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Straw mulching increases precipitation storage rather than water use efficiency and dryland winter wheat yield
Agricultural Water Management 206 (2018) 95–101
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Straw mulching increases precipitation storage rather than water use efficiency and dryland winter wheat yield
T
⁎
Jun Wanga,b, , Rajan Ghimirec, Xin Fua,b, Upendra M. Sainjud, Wenzhao Liue a
Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying Capacity, Northwest University, Xi’an 710127, China College of Urban and Environmental Science, Northwest University, Xi’an 710127, China c Agricultural Science Center, New Mexico State University, 2346 State Road 288, Clovis, NM 88101, USA d USDA-ARS, Northern Plains Agricultural Research Laboratory, 1500 North Central Avenue, Sidney, MT 59270, USA e CAS & MWR, Institute of Soil and Water Conservation, Yangling 712100, Shaanxi Province, China b
A R T I C LE I N FO
A B S T R A C T
Keywords: Soil water conservation Dryland farming Water use
Straw mulching is widely used to conserve soil water and increase crop yields. The effects of wheat straw mulching rate and method on dryland soil water storage, winter wheat (Triticum aestivum L.) growth and yield, and water-use efficiency (WUE) were examined from 2008 to 2015 in the Loess Plateau of China. Treatments included wheat straw mulching at a high rate of 9000 kg ha−1 (HSM) and low rate of 4500 kg ha−1 (LSM) throughout the year, straw mulching at a rate of 9000 kg ha−1 during summer fallow (FSM), and no mulching (CK). Soil water storage at wheat planting and precipitation-storage efficiency (PSE) were greater with straw mulching than without. Soil water storage at harvest was greater with HSM than CK and FSM. Wheat yield components such as number of wheat seedling, plant, tiller, and spike and thousand-grain weight varied with treatments and years, but wheat aboveground biomass and grain yields were usually greater with mulching than without during years with below-average precipitation. Harvest index and WUE were lower with LSM and HSM than other treatments in most years, but evapotranspiration did not vary with treatments. Overall, the increased PSE due to straw mulching did not increase yield and WUE, and straw mulching could sustain dryland wheat grain yield only in dry years.
1. Introduction Precipitation is one of the major factors dictating dryland crop production in the world. Reducing soil water evaporation, increasing precipitation storage efficiency (PSE) and improving crop water use efficiency are main challenges for sustaining dryland crop yields. During the last several decades, straw mulching has been widely used to conserve soil water and increase crop yields as well as to improve soil fertility and reduce erosion in arid and semiarid regions of Spain (Jordán et al., 2010), India (Chakraborty et al., 2008; Chakraborty et al., 2010; Sharma et al., 2011), USA (Baumhardt and Jones, 2002), and China (Su et al., 2007; Wang et al., 2012; Li et al., 2013; Wang and Shangguan, 2015; Zhang et al., 2015). In the northern Plain and Loess Plateau of China, it has been shown that straw mulching can improve wheat WUE by 10–20% compared with no mulching (Deng et al., 2006).
However, the effect of straw mulching on soil water conservation and crop yield has been highly variable, depending on mulching practices (Cook et al., 2006; Zhang et al., 2015), climate and soil conditions (Tolk et al., 1999; Stagnari et al., 2014; Wang et al., 2015). Chakraborty et al. (2010) found that wheat (T. aestivum L.) grain yield and water-use efficiency (WUE) were 13–25% greater with straw mulching than without in India. Jordán et al. (2010) found that soil available water was related with mulching rates by a polynomial function in southern Spain. In a three-year field experiment on the Loess Plateau of China, Zhang et al. (2015) found that soil water content at the 0–2 m soil layer increased by 1–23%, wheat yield by 13–23%, and WUE by 24–33% using wheat straw mulch compared with no mulch. However, Gao et al. (2009) found that mulching did not have a significant effect on wheat yield when soil water content at planting was high in the Loess Plateau of China. Similarly, Lu et al. (2014) reported that straw mulching increased soil water content, but reduced
Abbreviations: CK, no mulching; ET, evapotranspiration; FSM, wheat straw mulching at 9000 kg ha−1 during the summer fallow; HSM, wheat straw mulching at 9000 kg ha−1 throughout the year; LSM, wheat straw mulching at 4500 kg ha−1 throughout the year; PSE, precipitation-storage efficiency; SWH, soil water storage at harvest; SWP, soil water storage at planting; WUE, water-use efficiency ⁎ Corresponding author at: College of Urban and Environmental Science, Northwest University Xuefu Avenue No.1, Chang’an District, Xi’an 710127, China. E-mail address: [email protected] (J. Wang). https://doi.org/10.1016/j.agwat.2018.05.004 Received 4 January 2018; Received in revised form 7 May 2018; Accepted 7 May 2018 0378-3774/ © 2018 Elsevier B.V. All rights reserved.
Agricultural Water Management 206 (2018) 95–101
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The soil has an average bulk density of 1.30 Mg m−3, pH of 8.3, organic matter content of 10.50 g kg−1, total N of 0.80 g kg−1, alkaline dissolved N of 37.0 mg kg−1, total P of 0.66 g kg−1, Olsen P of 3.0 mg kg−1, exchangeable K of 129 mg kg−1, and CaCO3 of 108.4 g kg−1 at the 0–20 cm depth. The study had a randomized complete block design with four treatments and three replications. Treatments included control with no mulching (CK), wheat straw mulching throughout the year at 4500 kg ha−1 (LSM) and 9000 kg ha−1 (HSM), and wheat straw mulching during the summer fallow period (July to mid-September) at 9000 kg ha−1 (FSM). The plot size for each treatment was 6.7 m wide by 10 m long. Plots were tilled with a moldboard plow (Yili 1L-220, Shandong Yili Co.) to a depth of 20 cm after previous crop harvest in late June, hoed manually to 5 cm in mid-August, and cultivated with a rotary tiller to 20 cm in September before planting. Wheat straw cut to a length of 5–10 cm was applied at the soil surface by hand before winter wheat planting in LSM and HSM in September of every year. In FSM, wheat straw was applied immediately after previous crop harvest in late June and removed from the soil surface manually before planting in September. As the presence of decayed wheat straw can affect the germination and growth of winter wheat (Chen et al., 2009), wheat straw was removed at planting with FSM.
corn (Zea mays L.) yield and WUE compared with no mulching in silty clay loam soil in northeastern China with an annual precipitation of 573 mm. The neutral or negative effect of straw mulching may attribute to the potential seedlings death due to lower soil temperature in the early period (Gao and Li, 2005; Gao et al., 2009; Awe et al., 2015) and the reduction of soil N availability to crops by increasing N immobilization with straw application in the later growth stage (Lu et al., 2015). The Loess Plateau of China, with a 6000-yr-old agricultural history, encompasses a vast expanse of 620, 000 km2 area in northwestern China and is characterized by high precipitation variability (Wang et al., 2017). Winter wheat monoculture is one of the most common cropping systems in the drylands of the Loess Plateau, and wheat yield mainly depends on soil available water (Wang et al., 2011). Wheat straw mulching is typically used during the summer fallow period or throughout the year to conserve soil water and enhance crop yields (Deng et al., 2006; Zhang et al., 2015). Considering about 55–60% of annual precipitation occurred during summer fallow period from July through September in this region (Liu et al., 2010), the effect of straw mulching on soil water conservation and crop yield was not well compared between mulching during fallow and the whole agricultural year. Similarly, seasonal and interannual variability in precipitation may alter effect of wheat straw mulching on PSE, multiyear studies are needed to clarify the effects of straw mulching based on data of the whole year. In this study, we aimed to evaluate the effects of straw mulching rates and time on soil water storage at planting (SWP) and harvesting (SWH), PSE, evapotranspiration (ET), winter wheat growth and yield, and WUE from 2008 to 2015 compared with no mulching in the Loess Plateau of China. We hypothesized that straw mulching would increase SWP, SWH, PSE, winter wheat growth and yield, and WUE compared with no mulching, regardless of mulching rates and time.
2.2. Crop management Winter wheat (cultivar Chuangwu 134) was sown in late September or early October each year at seed rate of 165 kg ha−1 using a no-till disk drill with 20 cm row spacing, and harvested in late June in the following year. At planting, N fertilizer as urea (46% N) at 135 kg N ha−1 and phosphorus (P) fertilizer as calcium superphosphate (20% P) at 39 kg P ha−1 were broadcast and then incorporated to a depth of 20 cm using the rotary tiller. Potassium chloride fertilizer was not applied because of high potassium (K) content in the soil according to the soil test. All fertilizers were applied before straw mulching with HSM and LSM and after removing mulch with FSM or no mulching with CK in September. Hand weeding was done as needed to control weeds during wheat growing and fallow periods. No irrigation was applied.
2. Materials and methods 2.1. Experimental site and treatments The field experiment was carried out from 2008 to 2015 at the Changwu Agro-Ecological Research Station in the Loess Plateau (107° 44.70′ E, 35° 12.79′ N) in Changwu County, Shaanxi Province of China. The experimental site is 1220 m above the sea level and has a slope of < 1%. The site is located in the warm temperate zone with a continental monsoon climate. The average annual air temperature is 9.2 °C. The 24-yr average annual precipitation is 574 mm, more than half of which occurs from July to September (Table 1). The mean frost-free period is 194 d and the annual open pan evaporation is 1440 mm. The soil is a light silt loam (Heilutu series), which corresponds to a Calcarid Regosol in the FAO/UNESCO classification system (FAO/Unesco, 1988). The soil is with 35 g kg−1 sand, 656 g kg−1 silt, and 309 g kg−1 clay at the 0–20 cm depth. The average field capacity, saturation point, and soil wilting point are 0.29, 0.51, and 0.10 m3 m−3, respectively.
2.3. Measurements During the wheat growing season, seedling number, plant number, tiller per plant, and spike number were measured from two 1 m2 areas randomly within the plot in late October, early December, late March, and late June, respectively. In late June, total aboveground biomass (grains, stems, and leaves) was harvested by cutting all plants at a height of 2 cm above the ground manually from the entire plot without returning crop residues to the soil and weighed. A portion of the biomass was weighed, dried at 70 °C for 3 d to a uniform moisture level (Wang et al., 2011), and weighed again to determine dry matter yield, from which total biomass yield was determined. Grain yield was determined by threshing plants on the ground and measuring the yield on
Table 1 Precipitation during fallow (Pf, July to mid-September) and winter wheat growing season (Pg, late September to June of the following year) periods and total annual precipitation (Pt), drought index (DI) and precipitation type from 2008 to 2009 to 2014–2015. Year
Pf (mm)
DI for Pf
Type
Pg (mm)
DI for Pg
Type
Pt (mm)
DI for Pt
Type
2008–2009 2009–2010 2010–2011 2011–2012 2012–2013 2013–2014 2014–2015
324 280 458 449 346 395 323
−0.65 −1.29 1.32 1.19 −0.32 0.40 −0.66
Dry Dry Wet Wet Normal Wet Dry
162 195 232 210 154 244 287
−1.06 −0.36 0.43 −0.04 −1.23 0.68 1.60
Dry Dry Wet Normal Dry Wet Wet
486 475 690 659 500 639 610
−1.04 −1.17 1.22 0.88 −0.89 0.66 0.33
Dry Dry Wet Wet Dry Wet Normal
7-yr average
368
212
580
Dry, normal and wet year are classified by DI > − 0.35, −0.35 ≤ DI ≤ 0.35, and 0.35 < DI, respectively. 96
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oven-dried basis after drying a subsample at 70 °C for 3 d. Harvest index was calculated by dividing grain yield by total aboveground biomass yield. Soil water content was measured to a depth of 2 m at both planting (SWP) and harvest (SWH) in each year with a neutron probe. The neutron probe was placed in the center of the plot and calibrated against gravimetrically measured soil water content. Water content was measured at 0.1-m intervals for the 0–1 m layer and at 0.2-m intervals for the 1–2 m layer. Total soil water storage to 2 m was determined by adding water contents from all depth intervals. Daily total precipitation was recorded by an automatic weather station throughout the experimental period. There were boarder dikes around each plot to prevent water flow, so the surface runoff was considered negligible. No irrigation was applied during the experimental period. The groundwater table remained at a depth of about 60 m belowground (Li, 1983). According to our previous study, soil water within 2 m profile was not recharged completely after the summer fallow in most years for winter wheat monoculture system at the experimental site (Wang et al., 2011). Therefore, both drainage and the upward flow into the root zone was not considered. The intensity of the precipitation received was not high enough to observe significant drainage at the research site. Since precipitation is the sole water supply in the rainfed areas of the Loess Plateau, the PSE (Nielsen and Vigil, 2010; Wang et al., 2011) was calculated as: PSE (%) = (SWP-SWH’)/Pf
Table 2 Effect of wheat straw mulching on soil water storage at planting (SWP) and harvest (SWH), precipitation-storage efficiency (PSE), evapotranspiration (ET), and winter wheat water use efficiency (WUE) averaged across years.
−1
WUE (kg ha
mm
−1
) = Y/ET
SWH (mm)2
PSE (%)3
ET (mm)
WUE (kg ha−1 mm−1)
CK LSM HSM FSM Significance Treatment Year Treatment × Year
337 348 351 346
255 259 267 252
24.3 27.4 26.6 28.2
294 302 296 306
19.1 16.3 15.9 17.9
NS *** NS
*** *** ***
** *** NS
b a a a
b ab a b
** *** NS
*** *** ***
b a ab a
a c c b
3. Results
(1) 3.1. Precipitation About 53% of the total annual precipitation occurred during the summer fallow period (July to mid-September) (Table 1). Based on the DI, three precipitation year types were distinguished as normal (2014–2015), dry (2008–2009, 2009–2010 and 2012–2013) and wet (2010–2011, 2011–2012 and 2013–2014) years. Discrepancies were found between precipitation during fallow and growing season within the year of 2011–2012, 2012–2013 and 2014–2015. A dry fallow and a wet growing stage were found in the normal year of 2014–2015.
(2) (3)
3.2. Soil water storage and precipitation-use efficiency
where Pg is the precipitation during the growing season and Y is the grain yield of winter wheat. The drought index (DI) for annual precipitation (Xing et al., 2001) was calculated using the following equation to assess variations and status in precipitation among different years: DI = (P−M)/σ
SWP (mm)2
Numbers followed by different letters within a column are significantly different at P ≤ 0.05 by the least significance difference test. NS, not significant, ** and *** significant at p ≤ 0.01 and p ≤ 0.001 levels. 1 Treatments are CK, no mulching; FSM, wheat straw mulching at 9000 kg ha−1 during summer fallow; HSM, wheat straw mulching at 9000 kg ha−1 throughout the year; and LSM, wheat straw mulching at 4500 kg ha−1 throughout the year. 2 Both SWP and SWH was averaged for 7 years from 2008 to 2015. 3 PSE was average was averaged for 6 years from 2009 to 2015.
where Pf is the total precipitation during the fallow period, and SWP and SWH’ are soil water at wheat planting and at harvest of previous year’s wheat, respectively. As wheat was grown during the winter, water losses due to plant interception and evaporation from plant surfaces were considered negligible (Nielsen and Vigil, 2010; Wang et al., 2013). Therefore, the ET and WUE during the winter wheat growing season were calculated as ET (mm) = (SWP-SWH) + Pg
Treatment1
The SWP, SWH, and PSE varied among treatments, with a significant treatment × year interaction for PSE (Table 2). Averaged across years, SWP was 3–4% greater with straw mulching than no mulching. The SWH was 5% greater with HSM than CK. Among years, SWP and SWH were greater in 2011–2012 than other years. In 2009–2010, PSE was greater with HSM than CK and FSM (Table 3). The PSE was greater with FSM in 2010–2011, and lower with CK in 2012–2013 than other treatments in the respective year. In 2014–2015, PSE was greater with FSM than HSM. Averaged across years, PSE was 13–16% greater with LSM and FSM than CK (Table 2). Averaged across treatments, PSE was greater in 2014–2015 than other years.
(4)
Where P is the annual precipitation, M is the average precipitation, and is the standard deviation for precipitations. Precipitation year type was classified as the wet, normal and dry when DI is > 0.35, −0.35−0.35 and < −0.35, respectively (Xing et al., 2001). Similarly, the DIs for precipitation during fallow and growing periods were calculated to assess the status in seasonal precipitation among different years.
3.3. Winter wheat growth and yield Number of seedling, tiller, plant, and spike, aboveground biomass and grain yields, thousand-grain weight, and harvest index of winter wheat varied among treatments and years, with significant treatment × year interaction (Table 4). Seedling number was greater with FSM than LSM and HSM in 2009–2010 and 2011–2012, but was greater with CK or LSM than FSM in 2010–2011 and 2012–2013 (Table 5). Plant number was greater with CK than FSM in 2009–2010 and 2011–2012, but was greater with LSM or HSM than CK in 2010–2011 and 2012–2013. In 2013–2014 and 2014–2015, plant number was greater with FSM or HSM than other treatments. Tiller number was greater with HSM than CK in 2008–2009, 2010–2011, 2012–2013, and 2014–2015. In contrast, tiller number was greater with CK than HSM and FSM in 2009–2010 and 2011–2012. In 2013–2014, tiller number
2.4. Data analysis Data for soil water and wheat parameters were analyzed using the MIXED procedure of SAS (Littell et al., 1996). Mulching, year, and mulching × year interaction were considered as fixed effects and replication as the random effect. Means were separated by using the Fisher’s protected least significant difference test when treatments and interactions were significant. Unless otherwise stated, the differences among treatments and treatment × year interaction were considered significant at P ≤ 0.05. Relationship between WUE and PSE was analyzed using a regression (PROC REG) procedure.
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Table 3 Effect of wheat straw mulching on precipitation-storage efficiency (PSE) and winter wheat water-use efficiency (WUE) from 2008 to 2009 to 2014–2015. Treatment1 SWP (mm) CK LSM HSM FSM SWH (mm) CK LSM HSM FSM PSE (%) CK LSM HSM FSM ET (mm) CK LSM HSM FSM WUE (kg ha−1 mm−1) CK LSM HSM FSM
2008–2009
2009–2010
2010–2011
2011–2012
2012–2013
2013–2014
2014–2015
315 319 315 308
297 322 327 311
b a a ab
361 369 370 370
368 374 371 369
320 331 353 339
340 352 351 346
360 372 374 376
238 236 231 229
229 235 257 214
ab ab a b
259 256 259 261
265 263 273 265
253 261 271 257
251 259 268 256
290 300 311 281
– – – –
21.2 31.0 34.2 29.4
c ab a b
28.8 29.2 24.8 34.1
24.3 26.2 24.9 24.1
15.7 20.0 23.0 21.5
21.9 23.1 20.1 22.7
33.7 35.1 32.8 37.2
ab ab b a
239 245 245 241
263 282 265 292
312 320 307 315
220 224 235 236
333 337 327 335
356 359 350 382
ab ab b a
19.4 17.2 18.9 19.6
a b a a
17.4 17.6 18.7 16.9
b b b a
335 345 344 341 ab ab a b
16.4 14.6 13.1 14.1
a b b b
22.0 19.4 20.3 20.9
a b ab ab
24.6 22.8 21.6 22.3
c bc a ab
b a a a
a b b b
24.3 19.0 15.3 23.7
a b c a
b a a a
12.2 a 7.2 c 7.6 c 10.6 b
Numbers followed by different letters within a column are significantly different at P ≤ 0.05 by the least significance difference test. NS, not significant, ** and *** significant at p ≤ 0.01 and p ≤ 0.001 levels. 1 Treatments are CK, no mulching; FSM, wheat straw mulching at 9000 kg ha−1 during summer fallow; HSM, wheat straw mulching at 9000 kg ha−1 throughout the year; and LSM, wheat straw mulching at 4500 kg ha−1 throughout the year.
was greater with FSM than HSM in 2009–2010, 2010–2011, and 2011–2012, but greater with CK than other treatments in 2012–2013 and 2013–2014. Harvest index was lower with LSM than other treatments in 2008–2009. In 2009–2010, 2010–2011, and 2011–2012, harvest index was greater with CK than HSM. In 2012–2013, 2013–2014, and 2014–2015, harvest index was greater with CK and FSM than LSM and HSM. Averaged across years, seedling number was greater with CK than HSM (Table 4). Tiller and plant numbers were greater with LSM and HSM than CK and FSM, but the trend reversed for grain yield and harvest index. Spike number and thousand-grain weight were greater with FSM than other treatments. Aboveground biomass yield was greater with HSM than CK. Grain yield was not significantly different between CK and FSM, and they were greater than HSM and LSM. Among years, number of seedling, plant, tiller, and spike were, respectively, greater in 2008–2009, 2009–2010, 2010–2011, and
was greater with FSM than LSM and HSM. Spike number was greater with LSM and FSM than CK in 2008–2009 and 2009–2010. In 2010–2011 and 2011–2012, spike number was greater with LSM than other treatments. Spike number was greater with FSM than LSM and HSM in 2012–2013 and 2014–2015 and greater with HSM than LSM and FSM in 2013–2014. Aboveground biomass yield was greater with LSM or HSM than CK or FSM in 20008–2009, 2009–2010, 2010–2011, and 2012–2013 (Table 6). Biomass was greater with FSM than LSM in 2011–2012 and 2013–2014, but was greater with CK than other treatments in 2014–2015. Grain yield was lower with LSM in 2008–2009, but higher with CK in 2010–2011 than other treatments. In 2009–2010, grain yield was greater in LSM and HSM than CK. Grain yield was greater with CK and FSM than LSM and HSM in 2011–2012, 2013–2014, and 2014–2015. The 1000-grain weight was greater with LSM or HSM than other treatments in 2008–2009 and 2014–2015. The 1000-grain weight
Table 4 Effect of wheat straw mulching on number of winter wheat seedlings, plants, tillers, and spikes, thousand-grain weight, aboveground biomass and grain yields, and harvest index averaged across years. Treatment1
Seedling number (million ha−1)
Tiller number (plant−1)
Plant number (million ha−1)
Spike number (million ha−1)
Thousandgrain weight (g)
Aboveground biomass yield (Mg ha−1)
Grain yield (Mg ha−1)
Harvest index
CK LSM HSM FSM Significance Treatment Year Treatment × year
2.08 2.07 2.05 2.07
6.25 6.50 6.53 6.41
13.6 14.0 14.0 13.8
4.39 4.63 4.32 4.73
45.5 45.3 45.4 46.0
14.2 14.9 15.1 14.6
5.63 4.93 4.72 5.46
0.402 0.333 0.315 0.378
*** *** ***
a ab b ab
*** *** ***
c a a b
*** *** ***
b a a b
c b c a
*** *** ***
*** *** ***
b b b a
*** *** ***
b ab a ab
*** *** ***
a b b a
a b b a
*** *** ***
Numbers followed by different letters within a column are significantly different at P ≤ 0.05 by the least significance difference test. *** significant at p ≤ 0.001 levels. 1 Treatments are CK, no mulching; FSM, wheat straw mulching at 9000 kg ha−1 during summer fallow; HSM, wheat straw mulching at 9000 kg ha−1 throughout the year; and LSM, wheat straw mulching at 4500 kg ha−1 throughout the year. 98
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Table 5 Effect of wheat straw mulching on number of winter wheat seedling, plants, tiller and spikes from 2008 to 2009 to 2014–2015. Treatment1
2008–2009
2009–2010
2010–2011
2011–2012
2012–2013
2013–2014
2014–2015
2.34 2.33 2.31 2.37
ab bc c a
1.92 1.91 1.83 1.86
a a b b
2.07 2.03 2.04 2.08
ab b b a
2.07 2.08 2.05 2.04
ab a ab b
2.28 2.28 2.29 2.28
1.40 1.38 1.37 1.39
15.6 15.3 15.3 15.1
a ab ab b
12.7 14.3 13.8 13.8
c a b b
13.9 13.2 12.8 13.5
a b c b
12.5 13.0 13.0 12.7
b a a ab
15.3 15.1 14.9 15.7
b bc c a
11.9 13.9 14.3 12.7
d b a c
6.70 6.63 6.57 6.37
a ab b c
6.63 7.50 7.53 7.43
b a a a
6.70 6.53 6.30 6.50
a b c b
6.07 6.23 6.33 6.23
c b a b
6.73 6.60 6.53 6.90
ab bc c a
5.67 6.70 7.00 6.10
d b a c
4.46 4.75 4.81 4.83
b a a a
4.34 4.60 4.13 4.43
b a c b
5.00 5.14 4.76 4.90
b a d c
2.96 2.90 2.80 3.00
ab b c a
6.90 6.87 6.97 6.53
ab b a c
2.76 3.24 2.67 4.49
c b c a
−1
Seedling number (million ha ) CK 2.51 LSM 2.51 HSM 2.48 FSM 2.51 Plant number (million ha−1) CK 13.2 LSM 13.4 HSM 13.5 FSM 13.5 Tiller number (plant−1) CK 5.27 b LSM 5.33 ab HSM 5.47 a FSM 5.37 ab Spike number (million ha−1) CK 4.37 b LSM 4.91 a HSM 4.15 b FSM 4.96 a
Numbers followed by different letters within a column are significantly different at p ≤ 0.05 by the least significance difference test. 1 Treatments are CK, no mulching; FSM, wheat straw mulching at 9000 kg ha−1 during summer fallow; HSM, wheat straw mulching at 9000 kg ha−1 throughout the year; and LSM, wheat straw mulching at 4500 kg ha−1 throughout the year.
2013–2014 than other years (Table 5). Grain yield and aboveground biomass were greater in 2013–2104 and harvest index and thousandgrain weight were greater in 2011–2012 than other years.
were greater in 2012–2013 and 2013–2014 than other years (Table 3). The WUE decreased as PSE increased for all treatments, except for HSM (Fig. 1).
3.4. Evapotranspiration and water use efficiency
4. Discussion
The ET did not vary among treatments, but varied among years (Table 2). The WUE varied among treatments and years, with a significant treatment × year interaction. The WUE was lower with LSM in 2008–2009, but greater with CK in 2010–2011, 2012–2013, and 2014–15 than other treatments (Table 3). The WUE was greater with HSM than FSM in 2009–2010 and greater with CK than LSM in 2011–2012. In 2013–2014, WUE was greater with CK and FSM than LSM and HSM. Averaged across years, WUE was greater with CK than other treatments (Table 2). Averaged across treatments, ET and WUE
Straw mulching increased SWP by 3–4% and PSE by 8–16% compared with no mulching, and the effect was more obvious in below average precipitation years than above average precipitation years suggesting that straw mulching could be a good water conservation strategy for dry areas. Higher soil water storage with straw mulching may result from reducing evaporation by providing an insulation layer (Baumhardt and Jones, 2002) and lowering the daily soil temperature and/or from increasing rainfall infiltration and hydraulic conductivity during the summer period (Scott et al., 2010; Awe et al., 2015). Higher
Table 6 Effect of wheat straw mulching on winter wheat biomass and grain yields, harvest index, and thousand-grain weight from 2008 to 2009 to 2014–2015. Treatment1
2008–2009
2009–2010
2010–2011
2011–2012
2012–2013
2013–2014
2014–2015
4.60 4.98 4.93 4.91
b a a ab
5.47 5.02 4.50 4.78
a b c bc
6.87 6.22 6.23 6.57
a b b a
5.40 5.11 5.08 5.25
8.08 6.39 5.01 7.95
a b c a
4.36 2.58 2.66 4.05
a b b a
10.6 15.7 17.4 13.0
d b a c
13.0 13.0 13.5 12.0
b b a c
14.4 13.7 14.3 14.7
ab b ab a
12.8 14.2 14.7 13.2
22.4 21.3 20.5 23.6
b c c a
13.0 11.9 11.9 12.1
a b b b
−1
Grain yield (Mg ha ) CK 4.67 a LSM 4.23 b HSM 4.65 a FSM 4.73 a Aboveground biomass (Mg ha−1) CK 13.0 b LSM 14.3 a HSM 13.5 ab FSM 13.2 b Harvest index CK 0.359 a LSM 0.296 b HSM 0.343 a FSM 0.358 a Thousand-grain weight (g) CK 47.5 c LSM 49.7 a HSM 49.1 b FSM 49.4 b
0.437 0.317 0.282 0.377 43.6 43.1 42.4 45.2
a c d b
b c d a
0.421 0.388 0.332 0.398 48.7 45.7 45.1 49.2
a b c ab
0.476 0.454 0.437 0.448
b c d a
50.4 51.5 50.2 50.6
a ab b b
ab ab b a
b a a b
0.423 0.360 0.345 0.396 44.2 43.4 42.7 42.1
a b b a
a b c d
0.361 0.300 0.243 0.337 46.4 45.0 45.4 44.2
a b b c
a b c a
0.336 0.217 0.222 0.335 38.1 38.6 42.9 41.6
a b b a
d c a b
Numbers followed by different letters within a column are significantly different at p ≤ 0.05 by the least significance difference test. 1 Treatments are CK, no mulching; FSM, wheat straw mulching at 9000 kg ha−1 during summer fallow; HSM, wheat straw mulching at 9000 kg ha−1 throughout the year; and LSM, wheat straw mulching at 4500 kg ha−1 throughout the year. 99
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(Table 4), a result of increased soil water availability (Table 2). Such effects were pronounced more during the normal or dry years than the wet years (Tables 5 and 6). Straw mulching throughout the year (LSM and HSM) reduced wheat grain yield and harvest index at the cost of biomass yield compared with CK and FSM (Table 4). It is likely that increased soil water availability due to straw mulching throughout the year favored early biomass growth due to increased plant and tiller numbers but soil may not have stored enough moisture to continue yield formation. Studies show that water deficit in any period of winter wheat development can result in a substantial decline in the yield and efficiency with which soil water reserves are utilized (Verda et al., 2014). Besides, straw mulching also affects soil nutrient dynamics and thereby wheat yield (Lu et al., 2015). Although we did not measure soil N content, straw mulch applied at planting possibly immobilized soil inorganic N, thereby reducing N availability and grain yield. In southern Australia, Scott et al. (2010) found that the concentration of Nitrate-N in soil solution decreased as the rate of straw amount as mulch increased. Addition of crop residue with high C/N ratio, such as wheat straw, can reduce N availability to crops by increasing N immobilization (Lu et al., 2015). Gao et al. (2009) reported that straw mulching favored more wheat vegetative than reproductive growth compared with no mulching. Straw mulching during fallow, however, produced similar grain yield and harvest index compared with no mulching, suggesting that straw mulching is only beneficial when applied during the fallow period and that additional N fertilization may be needed to increase wheat grain yield when mulch is applied. The effectiveness of year-round straw mulching in increasing grain and biomass yields was evident during the dry years, such as in 2008–2009, 2009–2010, and 2012–2013, when grain and biomass yields were greater with HSM or LSM than other treatments (Tables 1 and 6). The trends reversed in the wet years. This suggests that straw mulching is beneficial in sustaining wheat yield only during dry periods. Several researchers (Chen et al., 2013; Lu et al., 2014, 2015) have reported that wheat straw mulching increased winter wheat yields compared with no mulching when soil water content is low. BalwinderSingh et al. (2011) found that mulching improved crop growth and yield attributes when water was limiting in northwest India, however this only led to significantly higher yield when there was prolonged water stress prior to anthesis. In a meta-analysis of the effect of straw mulching on soil water content and wheat yield, Wang et al. (2015) found that wheat straw mulching improved winter wheat yield compared with no mulching when annual precipitation was < 250 mm. Straw mulching during fallow or no mulching increased harvest index than other treatments in most years by enhancing grain yield relative to total biomass yield in this study. Although straw mulching increased SWP, it did not affect ET (Table 2), suggesting that wheat consumed similar amount of water, regardless of treatments. Greater amount of water may have used in early biomass growth leading to greater biomass in mulched treatments, but no difference in grain yield and reduced WUE with LSM and HSM compared with other treatments. Some researchers (Huang et al., 2005; Lenssen et al., 2014) have reported linear relationship between wheat grain yield and WUE. Our results, however, were in contrast to those reported for greater WUE with straw mulching than without in the semiarid areas (Deng et al., 2006; Chakraborty et al., 2010). Straw mulching reduced WUE compared with no mulching, specifically, during years with > 500 mm annual precipitation. Above-average growing season precipitation increased PSE, but reduced wheat growth and yield parameters as well as WUE in 2014–2015 than other years (Tables 1, 3, 5, and 6). Increased soil water recharge during the fallow increased PSE in 2014–2015. This, followed by increased precipitation during the growing season, resulted in anaerobic condition, which may have reduced wheat growth, yield, and WUE in 2014–2015. Straw mulching appears to be beneficial compared with no mulching for increasing PSE during the dry years, but not necessarily increase WUE
Fig. 1. Relationship between water use efficiency (WUE) and precipitation storage efficiency (PSE) under different treatments. Treatments are CK, no mulching; FSM, wheat straw mulching at 9000 kg ha−1 during summer fallow; HSM, wheat straw mulching at 9000 kg ha−1 throughout the year; and LSM, wheat straw mulching at 4500 kg ha−1 throughout the year. The solid, dot, dash and dash-dot lines were fitted for CK, LSM, FSM and HSM, respectively. The n.s. means the fitting was not significant.
rate of straw mulching conserved more soil water until crop harvest than mulching during fallow or no mulching, as shown by greater SWH with HSM than CK and FSM. This is in agreement with that reported by Stagnari et al. (2014) in a Mediterranean environment. Decomposition of wheat residue due to higher soil temperature and water content during fallow and shorter duration of mulching probably reduced the effectiveness of FSM to conserve soil water at wheat harvest in the present study. Only 24–28% of the total precipitation during summer fallow was stored in the soil (Table 2), a case similar to that reported by Wang et al. (2011) in the Loess Plateau of China. Straw mulching applied either at lower rate throughout the year or at higher rate during fallow was more effective in increasing PSE than no mulching, a result of reduced water loss due to evaporation. Baumhardt et al. (2013) also found that PSE was greater with wheat residue cover than without under cotton (Gossipium hirsutum L.) in the southern high plain of USA. Straw mulching during fallow period increased PSE during years with wet fallows. In contrast, year-round mulching, specifically HSM, increased PSE during years with a dry fallow, such as in 2009–2010 (Tables 1 and 3). However, increased PSE due to straw mulching did not improve WUE leading to low or no effects on wheat yield (Fig. 1). It is likely that some of the wheat straw used for mulching contributed to soil organic matter accumulation, and thereby increased SWP and PSE (Iqbal et al., 2011; Wang et al., 2011). It may take several years to see the effects of increased soil organic matter due to straw mulching to show difference in water use efficiency. Higher PSE with mulching generally resulted in greater soil water storage at planting (Table 2), which can enhance the germination and growth of wheat in dryland farming systems, but may not be enough to support yield formation and increase WUE (Deng et al., 2006). Increased SWP and PSE with LSM and HSM translated into enhanced wheat plant stand and tiller numbers (Tables 2 and 4), probably due to greater soil water availability for early growth of the crop. The lower seedling number with HSM appeared to be a result of death of some seedlings due to lower soil temperature at planting from high rate of mulching, a case similar to that observed by several researchers (Gao and Li 2005; Awe et al., 2015). This occurred, specifically, during years with dry growing season, such as 2009–2010 and 2012–2013 (Tables 1 and 5). Straw mulching during fallow (FSM) appeared to have a beneficial effect in increasing wheat spike number with heavier grains 100
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and wheat yield during years with > 500 mm annual precipitation. Wheat straw mulching could be a good strategy to mitigate drought impacts in drylands of Loess Plateau and similar agroecosystems.
FAO/Unesco, 1988. Soil Map of the World, Revised Legend. FAO, Rome. Gao, Y.J., Li, S.X., 2005. Cause and mechanism of crop yield reduction under straw mulch in dryland. Trans. CSAE 21, 15–19 in Chinese with English abstract. Gao, Y., Li, Y., Zhang, J., Liu, W., Dang, Z., Cao, W., Qiang, Q., 2009. Effects of mulch, N fertilizer, and plant density on wheat yield wheat nitrogen uptake, and residual soil nitrate in a dryland area of China. Nutr. Cycl. Agroecosyst. 85, 109–121. Huang, Y., Chen, L., Fu, B., Huang, Z., Gong, J., 2005. The wheat yields and water-use efficiency in the Loess Plateau: straw mulch and irrigation effects. Agric. Water Manage. 72, 209–222. Iqbal, M., Anwarul, H., Es, H.M.V., 2011. Influence of residue management and tillage systems on carbon sequestration and nitrogen phosphorus, and potassium dynamics of soil and wheat production in semi-arid region. Commun. Soil Sci. Plan. 42, 528–547. Jordán, A., Zavala, L.M., Gil, J., 2010. Effects of mulching on soil physical properties and runoff under semi-arid conditions in southern Spain. Catena 81, 77–85. Lenssen, A.W., Sainju, U.M., Iversen, W.M., Allen, B.L., Evans, R.G., 2014. Crop diversification, tillage, and management influences on spring wheat yield and soil water use. Agron. J. 106, 1445–1454. Li, S.X., Wang, Z.H., Li, S.Q., Gao, Y.J., Tian, X.H., 2013. Effect of plastic sheet mulch, wheat straw mulch, and maize growth on water loss by evaporation in dryland areas of China. Agric. Water Manage. 116, 39–49. Li, Y.S., 1983. The properties of water cycle in soil and their effect on water cycle for land in the Loess Plateau. Acta Ecol. Sin. 3, 91–101 In Chinese. Littell, R.C., Milliken, G.A., Stroup, W.W., Wolfinger, R.D., 1996. SAS System for Mixed Models. SAS Inst. Inc., Cary, NC. Liu, W., Zhang, X.C., Dang, T., Ouyang, Z., Li, Z., Wang, J., Wang, R., Gao, C., 2010. Soil water dynamics and deep soil recharge in a record wet year in the southern loess plateau of China. Agric. Water Manage 97, 1133–1138. Lu, X., Li, S., Bu, Q., Cheng, D., Duan, W., Sun, Z., 2014. Effects of rainfall harvesting and mulching on corn yield and water use in the corn belt of northeast China. Agron. J. 106, 2175–2184. Lu, X., Li, Z., Sun, Z., Bu, Q., 2015. Straw mulching reduces maize yield, water, and nitrogen use in northeastern China. Agron. J. 107, 406–414. Nielsen, D.W., Vigil, M.F., 2010. Precipitation storage efficiency during fallow in wheatfallow systems. Agron. J. 10, 537–543. Scott, B.J., Eberbach, P.L., Evans, J., Wade, L.J., 2010. In: Clayton, E.H., Burns, H.M. (Eds.), EH Graham Centre Monograph No. 1: Stubble Retention in Cropping Systems in Southern Australia: Benefits and Challenges. Industry & Investment NSW, Orange. Sharma, P., Abrol, V., Sharma, R.K., 2011. Impact of tillage and mulch management on economics energy requirement and crop performance in maize-wheat rotation in rainfed subhumid inceptisols, India. Eur. J. Agron. 34, 46–51. Stagnari, F., Galieni, A., Speca, S., Cafiero, G., Pisante, M., 2014. Effects of straw mulch on growth and yield of durum wheat during transition to Conservation Agriculture in Mediterranean environment. Field Crop. Res. 167, 51–63. Su, Z., Zhang, J., Wu, W., Cai, D., Lv, J., Jiang, G., Huang, J., Gao, J., Hartmann, R., Gabriels, D., 2007. Effects of conservation tillage practices on winter wheat water-use efficiency and crop yield on the Loess Plateau. China. Agric. Water Manage. 87, 307–314. Tolk, J.A., Howell, T.A., Evett, S.R., 1999. Effect of mulch, irrigation, and soil type on water use and yield of maize. Soil Till. Res. 50, 137–147. Verda, B., Vida, G., Verda-Laszlo Bencze, S., Veisz, O., 2014. Effect of simulating drought in various phenophases on the water use efficiency of winter wheat. J. Agron Crop Sci. 201, 1–9. Wang, L., Shangguan, Z., 2015. Water–use efficiency of dryland wheat in response to mulching and tillage practices on the Loess Plateau. Sci. Rep. 5, 12225. Wang, J., Liu, W., Dang, T., 2011. Responses of soil water balance and precipitation storage efficiency to increased fertilizer application in winter wheat. Plant Soil 347, 41–51. Wang, X., Wu, H., Dai, K., Zhang, D., Feng, Z., Zhao, Q., Wu, X., Jin, K., Cai, D., Oenema, O., Hoogmoed, W.B., 2012. Tillage and crop residue effects on rainfed wheat and maize production in northern China. Field Crop. Res. 132, 106–116. Wang, J., Liu, W.Z., Dang, T.H., Sainju, U.M., 2013. Nitrogen fertilization effect on soil water and wheat yield in the Chinese Loess Plateau. Agron. J. 105, 143–149. Wang, L., Chen, J., Shangguan, Z., 2015. Yield responses of wheat to mulching practices in dryland farming on the loess plateau. PLoS One 10, e0127402. Wang, X., Jiao, F., Li, X., An, S., 2017. The loess plateau. In: Zhang, L., Schwarzel, K. (Eds.), Multifunctional Land-Use Systems for Managing the Nexus of Environmental Resources. United Nations University, Dresden, Germany, pp. 11–27. Xing, N.Q., Zhang, Y.Q., Wang, L.X., 2001. The Study on Dryland Agriculture in North China. Chinese Agriculture Press, Beijing. Zhang, P., Wei, T., Wang, H., Wang, M., Meng, X., Mou, S., Zhang, R., Jia, Z., Han, Q., 2015. Effects of straw mulch on soil water and winter wheat production in dryland farming. Sci. Rep. 5, 10725.
5. Conclusions Wheat straw mulching increased SWP, PSE, winter wheat seedling growth, plant, and tiller numbers compared with no mulching in the semiarid Loess Plateau of China. Mulching throughout the year, however, reduced spike number, grain yield, thousand-grain weight, harvest index, and water-use efficiency at the expense of aboveground biomass yield, but mulching during summer fallow maintained grain yield compared with no mulching. Mulching rate had little effect on soil water storage and wheat characteristics. Further study may confirm the benefit of straw mulching on N fertilization and SOC accrual, this revealed benefit of straw mulching on precipitation storage and wheat yield compared with no mulching, specifically during the dry years. It did not increase WUE and wheat yield during years with > 500 mm annual precipitation. Because of increased precipitation storage efficiency and similar wheat yields, straw mulching should be applied during fallow period or at low rate throughout the year in dry years to increase soil water conservation and improve agricultural sustainability in drylands. Acknowledgements This work was supported by the National Natural Science Foundation of China (grant numbers 31570440, 31270484) and the International Scientific and Technological Cooperation and Exchange Project of Shaanxi Province, China (grant number 2015KW-026). References Awe, G.O., Reichert, J.M., Wendroth, O.O., 2015. Temporal variability and covariance structures of soil temperature in a sugarcane field under different management practices in southern Brazil. Soil Till. Res. 150, 93–106. Balwinder-Singh, Eberbach, P.I., Humphreys, E., Kukal, S.S., 2011. The effect of rice straw mulch on evapotranspiration, transpiration, and soil evaporation of irrigated wheat in Punjab, India. Agric. Water Manage. 98, 1847–1855. Baumhardt, R.L., Jones, O.R., 2002. Residue management and tillage effects on soil-water storage and grain yield of dryland wheat and sorghum for a clay loam in Texas. Soil Till. Res. 68, 71–82. Baumhardt, R.L., Schwartz, R., Howell, T., Evett, S.R., Colaizzi, P., 2013. Residue management effects on water use and yield of deficit irrigated cotton. Agron. J. 105, 1026–1034. Chakraborty, D., Nagarajan, S., Aggarwal, P., Gupta, V.K., Tomar, R.K., Garg, R.N., Sahoo, R.N., Sarkar, A., Chopra, U.K., Sarma, K.S.S., Kalra, N., 2008. Effect of mulching on soil and plant water status: and the growth and yield of wheat (Triticum aestivum L.) in a semi-arid environment. Agric. Water Manage. 95, 1323–1334. Chakraborty, D., Garg, R.N., Tomar, R.K., Singh, R., Sharma, S.K., Singh, R.K., Trivedi, S.M., Mittal, R.B., Sharma, P.K., Kamble, K.H., 2010. Synthetic and organic mulching and nitrogen effect on winter wheat (Triticum aestivum L.) in a semi-arid environment. Agric. Water Manage. 97, 738–748. Chen, H.Q., Hou, R.X., Gong, Y.S., Li, H.W., Fan, M.S., Kuzyakov, K., 2009. Effects of 11 years of conservation tillage on soil organic matter fractions in wheat monoculture in Loess Plateau of China. Soil Till. Res. 106, 85–94. Chen, S.Y., Zhang, X.Y., Sun, H.Y., Shao, L.W., 2013. Cause and mechanism of winter wheat yield reduction under straw mulch in the North China Plain. Chin. J. EcoAgric. 21, 519–525 in Chinese with English Abstract. Cook, H.F., Valdes, G.S., Lee, H.C., 2006. Mulch effects on rainfall interception, soil physical characteristics and temperature under Zea mays L. Soil Till. Res. 91, 227–235. Deng, X.P., Shan, L., Zhang, H., Turner, N.C., 2006. Improving agricultural water use efficiency in arid and semiarid areas of China. Agric. Water Manage. 80, 23–40.
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Straw mulching increases precipitation storage rather than water use efficiency and dryland winter wheat yield
T
⁎
Jun Wanga,b, , Rajan Ghimirec, Xin Fua,b, Upendra M. Sainjud, Wenzhao Liue a
Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying Capacity, Northwest University, Xi’an 710127, China College of Urban and Environmental Science, Northwest University, Xi’an 710127, China c Agricultural Science Center, New Mexico State University, 2346 State Road 288, Clovis, NM 88101, USA d USDA-ARS, Northern Plains Agricultural Research Laboratory, 1500 North Central Avenue, Sidney, MT 59270, USA e CAS & MWR, Institute of Soil and Water Conservation, Yangling 712100, Shaanxi Province, China b
A R T I C LE I N FO
A B S T R A C T
Keywords: Soil water conservation Dryland farming Water use
Straw mulching is widely used to conserve soil water and increase crop yields. The effects of wheat straw mulching rate and method on dryland soil water storage, winter wheat (Triticum aestivum L.) growth and yield, and water-use efficiency (WUE) were examined from 2008 to 2015 in the Loess Plateau of China. Treatments included wheat straw mulching at a high rate of 9000 kg ha−1 (HSM) and low rate of 4500 kg ha−1 (LSM) throughout the year, straw mulching at a rate of 9000 kg ha−1 during summer fallow (FSM), and no mulching (CK). Soil water storage at wheat planting and precipitation-storage efficiency (PSE) were greater with straw mulching than without. Soil water storage at harvest was greater with HSM than CK and FSM. Wheat yield components such as number of wheat seedling, plant, tiller, and spike and thousand-grain weight varied with treatments and years, but wheat aboveground biomass and grain yields were usually greater with mulching than without during years with below-average precipitation. Harvest index and WUE were lower with LSM and HSM than other treatments in most years, but evapotranspiration did not vary with treatments. Overall, the increased PSE due to straw mulching did not increase yield and WUE, and straw mulching could sustain dryland wheat grain yield only in dry years.
1. Introduction Precipitation is one of the major factors dictating dryland crop production in the world. Reducing soil water evaporation, increasing precipitation storage efficiency (PSE) and improving crop water use efficiency are main challenges for sustaining dryland crop yields. During the last several decades, straw mulching has been widely used to conserve soil water and increase crop yields as well as to improve soil fertility and reduce erosion in arid and semiarid regions of Spain (Jordán et al., 2010), India (Chakraborty et al., 2008; Chakraborty et al., 2010; Sharma et al., 2011), USA (Baumhardt and Jones, 2002), and China (Su et al., 2007; Wang et al., 2012; Li et al., 2013; Wang and Shangguan, 2015; Zhang et al., 2015). In the northern Plain and Loess Plateau of China, it has been shown that straw mulching can improve wheat WUE by 10–20% compared with no mulching (Deng et al., 2006).
However, the effect of straw mulching on soil water conservation and crop yield has been highly variable, depending on mulching practices (Cook et al., 2006; Zhang et al., 2015), climate and soil conditions (Tolk et al., 1999; Stagnari et al., 2014; Wang et al., 2015). Chakraborty et al. (2010) found that wheat (T. aestivum L.) grain yield and water-use efficiency (WUE) were 13–25% greater with straw mulching than without in India. Jordán et al. (2010) found that soil available water was related with mulching rates by a polynomial function in southern Spain. In a three-year field experiment on the Loess Plateau of China, Zhang et al. (2015) found that soil water content at the 0–2 m soil layer increased by 1–23%, wheat yield by 13–23%, and WUE by 24–33% using wheat straw mulch compared with no mulch. However, Gao et al. (2009) found that mulching did not have a significant effect on wheat yield when soil water content at planting was high in the Loess Plateau of China. Similarly, Lu et al. (2014) reported that straw mulching increased soil water content, but reduced
Abbreviations: CK, no mulching; ET, evapotranspiration; FSM, wheat straw mulching at 9000 kg ha−1 during the summer fallow; HSM, wheat straw mulching at 9000 kg ha−1 throughout the year; LSM, wheat straw mulching at 4500 kg ha−1 throughout the year; PSE, precipitation-storage efficiency; SWH, soil water storage at harvest; SWP, soil water storage at planting; WUE, water-use efficiency ⁎ Corresponding author at: College of Urban and Environmental Science, Northwest University Xuefu Avenue No.1, Chang’an District, Xi’an 710127, China. E-mail address: [email protected] (J. Wang). https://doi.org/10.1016/j.agwat.2018.05.004 Received 4 January 2018; Received in revised form 7 May 2018; Accepted 7 May 2018 0378-3774/ © 2018 Elsevier B.V. All rights reserved.
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The soil has an average bulk density of 1.30 Mg m−3, pH of 8.3, organic matter content of 10.50 g kg−1, total N of 0.80 g kg−1, alkaline dissolved N of 37.0 mg kg−1, total P of 0.66 g kg−1, Olsen P of 3.0 mg kg−1, exchangeable K of 129 mg kg−1, and CaCO3 of 108.4 g kg−1 at the 0–20 cm depth. The study had a randomized complete block design with four treatments and three replications. Treatments included control with no mulching (CK), wheat straw mulching throughout the year at 4500 kg ha−1 (LSM) and 9000 kg ha−1 (HSM), and wheat straw mulching during the summer fallow period (July to mid-September) at 9000 kg ha−1 (FSM). The plot size for each treatment was 6.7 m wide by 10 m long. Plots were tilled with a moldboard plow (Yili 1L-220, Shandong Yili Co.) to a depth of 20 cm after previous crop harvest in late June, hoed manually to 5 cm in mid-August, and cultivated with a rotary tiller to 20 cm in September before planting. Wheat straw cut to a length of 5–10 cm was applied at the soil surface by hand before winter wheat planting in LSM and HSM in September of every year. In FSM, wheat straw was applied immediately after previous crop harvest in late June and removed from the soil surface manually before planting in September. As the presence of decayed wheat straw can affect the germination and growth of winter wheat (Chen et al., 2009), wheat straw was removed at planting with FSM.
corn (Zea mays L.) yield and WUE compared with no mulching in silty clay loam soil in northeastern China with an annual precipitation of 573 mm. The neutral or negative effect of straw mulching may attribute to the potential seedlings death due to lower soil temperature in the early period (Gao and Li, 2005; Gao et al., 2009; Awe et al., 2015) and the reduction of soil N availability to crops by increasing N immobilization with straw application in the later growth stage (Lu et al., 2015). The Loess Plateau of China, with a 6000-yr-old agricultural history, encompasses a vast expanse of 620, 000 km2 area in northwestern China and is characterized by high precipitation variability (Wang et al., 2017). Winter wheat monoculture is one of the most common cropping systems in the drylands of the Loess Plateau, and wheat yield mainly depends on soil available water (Wang et al., 2011). Wheat straw mulching is typically used during the summer fallow period or throughout the year to conserve soil water and enhance crop yields (Deng et al., 2006; Zhang et al., 2015). Considering about 55–60% of annual precipitation occurred during summer fallow period from July through September in this region (Liu et al., 2010), the effect of straw mulching on soil water conservation and crop yield was not well compared between mulching during fallow and the whole agricultural year. Similarly, seasonal and interannual variability in precipitation may alter effect of wheat straw mulching on PSE, multiyear studies are needed to clarify the effects of straw mulching based on data of the whole year. In this study, we aimed to evaluate the effects of straw mulching rates and time on soil water storage at planting (SWP) and harvesting (SWH), PSE, evapotranspiration (ET), winter wheat growth and yield, and WUE from 2008 to 2015 compared with no mulching in the Loess Plateau of China. We hypothesized that straw mulching would increase SWP, SWH, PSE, winter wheat growth and yield, and WUE compared with no mulching, regardless of mulching rates and time.
2.2. Crop management Winter wheat (cultivar Chuangwu 134) was sown in late September or early October each year at seed rate of 165 kg ha−1 using a no-till disk drill with 20 cm row spacing, and harvested in late June in the following year. At planting, N fertilizer as urea (46% N) at 135 kg N ha−1 and phosphorus (P) fertilizer as calcium superphosphate (20% P) at 39 kg P ha−1 were broadcast and then incorporated to a depth of 20 cm using the rotary tiller. Potassium chloride fertilizer was not applied because of high potassium (K) content in the soil according to the soil test. All fertilizers were applied before straw mulching with HSM and LSM and after removing mulch with FSM or no mulching with CK in September. Hand weeding was done as needed to control weeds during wheat growing and fallow periods. No irrigation was applied.
2. Materials and methods 2.1. Experimental site and treatments The field experiment was carried out from 2008 to 2015 at the Changwu Agro-Ecological Research Station in the Loess Plateau (107° 44.70′ E, 35° 12.79′ N) in Changwu County, Shaanxi Province of China. The experimental site is 1220 m above the sea level and has a slope of < 1%. The site is located in the warm temperate zone with a continental monsoon climate. The average annual air temperature is 9.2 °C. The 24-yr average annual precipitation is 574 mm, more than half of which occurs from July to September (Table 1). The mean frost-free period is 194 d and the annual open pan evaporation is 1440 mm. The soil is a light silt loam (Heilutu series), which corresponds to a Calcarid Regosol in the FAO/UNESCO classification system (FAO/Unesco, 1988). The soil is with 35 g kg−1 sand, 656 g kg−1 silt, and 309 g kg−1 clay at the 0–20 cm depth. The average field capacity, saturation point, and soil wilting point are 0.29, 0.51, and 0.10 m3 m−3, respectively.
2.3. Measurements During the wheat growing season, seedling number, plant number, tiller per plant, and spike number were measured from two 1 m2 areas randomly within the plot in late October, early December, late March, and late June, respectively. In late June, total aboveground biomass (grains, stems, and leaves) was harvested by cutting all plants at a height of 2 cm above the ground manually from the entire plot without returning crop residues to the soil and weighed. A portion of the biomass was weighed, dried at 70 °C for 3 d to a uniform moisture level (Wang et al., 2011), and weighed again to determine dry matter yield, from which total biomass yield was determined. Grain yield was determined by threshing plants on the ground and measuring the yield on
Table 1 Precipitation during fallow (Pf, July to mid-September) and winter wheat growing season (Pg, late September to June of the following year) periods and total annual precipitation (Pt), drought index (DI) and precipitation type from 2008 to 2009 to 2014–2015. Year
Pf (mm)
DI for Pf
Type
Pg (mm)
DI for Pg
Type
Pt (mm)
DI for Pt
Type
2008–2009 2009–2010 2010–2011 2011–2012 2012–2013 2013–2014 2014–2015
324 280 458 449 346 395 323
−0.65 −1.29 1.32 1.19 −0.32 0.40 −0.66
Dry Dry Wet Wet Normal Wet Dry
162 195 232 210 154 244 287
−1.06 −0.36 0.43 −0.04 −1.23 0.68 1.60
Dry Dry Wet Normal Dry Wet Wet
486 475 690 659 500 639 610
−1.04 −1.17 1.22 0.88 −0.89 0.66 0.33
Dry Dry Wet Wet Dry Wet Normal
7-yr average
368
212
580
Dry, normal and wet year are classified by DI > − 0.35, −0.35 ≤ DI ≤ 0.35, and 0.35 < DI, respectively. 96
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oven-dried basis after drying a subsample at 70 °C for 3 d. Harvest index was calculated by dividing grain yield by total aboveground biomass yield. Soil water content was measured to a depth of 2 m at both planting (SWP) and harvest (SWH) in each year with a neutron probe. The neutron probe was placed in the center of the plot and calibrated against gravimetrically measured soil water content. Water content was measured at 0.1-m intervals for the 0–1 m layer and at 0.2-m intervals for the 1–2 m layer. Total soil water storage to 2 m was determined by adding water contents from all depth intervals. Daily total precipitation was recorded by an automatic weather station throughout the experimental period. There were boarder dikes around each plot to prevent water flow, so the surface runoff was considered negligible. No irrigation was applied during the experimental period. The groundwater table remained at a depth of about 60 m belowground (Li, 1983). According to our previous study, soil water within 2 m profile was not recharged completely after the summer fallow in most years for winter wheat monoculture system at the experimental site (Wang et al., 2011). Therefore, both drainage and the upward flow into the root zone was not considered. The intensity of the precipitation received was not high enough to observe significant drainage at the research site. Since precipitation is the sole water supply in the rainfed areas of the Loess Plateau, the PSE (Nielsen and Vigil, 2010; Wang et al., 2011) was calculated as: PSE (%) = (SWP-SWH’)/Pf
Table 2 Effect of wheat straw mulching on soil water storage at planting (SWP) and harvest (SWH), precipitation-storage efficiency (PSE), evapotranspiration (ET), and winter wheat water use efficiency (WUE) averaged across years.
−1
WUE (kg ha
mm
−1
) = Y/ET
SWH (mm)2
PSE (%)3
ET (mm)
WUE (kg ha−1 mm−1)
CK LSM HSM FSM Significance Treatment Year Treatment × Year
337 348 351 346
255 259 267 252
24.3 27.4 26.6 28.2
294 302 296 306
19.1 16.3 15.9 17.9
NS *** NS
*** *** ***
** *** NS
b a a a
b ab a b
** *** NS
*** *** ***
b a ab a
a c c b
3. Results
(1) 3.1. Precipitation About 53% of the total annual precipitation occurred during the summer fallow period (July to mid-September) (Table 1). Based on the DI, three precipitation year types were distinguished as normal (2014–2015), dry (2008–2009, 2009–2010 and 2012–2013) and wet (2010–2011, 2011–2012 and 2013–2014) years. Discrepancies were found between precipitation during fallow and growing season within the year of 2011–2012, 2012–2013 and 2014–2015. A dry fallow and a wet growing stage were found in the normal year of 2014–2015.
(2) (3)
3.2. Soil water storage and precipitation-use efficiency
where Pg is the precipitation during the growing season and Y is the grain yield of winter wheat. The drought index (DI) for annual precipitation (Xing et al., 2001) was calculated using the following equation to assess variations and status in precipitation among different years: DI = (P−M)/σ
SWP (mm)2
Numbers followed by different letters within a column are significantly different at P ≤ 0.05 by the least significance difference test. NS, not significant, ** and *** significant at p ≤ 0.01 and p ≤ 0.001 levels. 1 Treatments are CK, no mulching; FSM, wheat straw mulching at 9000 kg ha−1 during summer fallow; HSM, wheat straw mulching at 9000 kg ha−1 throughout the year; and LSM, wheat straw mulching at 4500 kg ha−1 throughout the year. 2 Both SWP and SWH was averaged for 7 years from 2008 to 2015. 3 PSE was average was averaged for 6 years from 2009 to 2015.
where Pf is the total precipitation during the fallow period, and SWP and SWH’ are soil water at wheat planting and at harvest of previous year’s wheat, respectively. As wheat was grown during the winter, water losses due to plant interception and evaporation from plant surfaces were considered negligible (Nielsen and Vigil, 2010; Wang et al., 2013). Therefore, the ET and WUE during the winter wheat growing season were calculated as ET (mm) = (SWP-SWH) + Pg
Treatment1
The SWP, SWH, and PSE varied among treatments, with a significant treatment × year interaction for PSE (Table 2). Averaged across years, SWP was 3–4% greater with straw mulching than no mulching. The SWH was 5% greater with HSM than CK. Among years, SWP and SWH were greater in 2011–2012 than other years. In 2009–2010, PSE was greater with HSM than CK and FSM (Table 3). The PSE was greater with FSM in 2010–2011, and lower with CK in 2012–2013 than other treatments in the respective year. In 2014–2015, PSE was greater with FSM than HSM. Averaged across years, PSE was 13–16% greater with LSM and FSM than CK (Table 2). Averaged across treatments, PSE was greater in 2014–2015 than other years.
(4)
Where P is the annual precipitation, M is the average precipitation, and is the standard deviation for precipitations. Precipitation year type was classified as the wet, normal and dry when DI is > 0.35, −0.35−0.35 and < −0.35, respectively (Xing et al., 2001). Similarly, the DIs for precipitation during fallow and growing periods were calculated to assess the status in seasonal precipitation among different years.
3.3. Winter wheat growth and yield Number of seedling, tiller, plant, and spike, aboveground biomass and grain yields, thousand-grain weight, and harvest index of winter wheat varied among treatments and years, with significant treatment × year interaction (Table 4). Seedling number was greater with FSM than LSM and HSM in 2009–2010 and 2011–2012, but was greater with CK or LSM than FSM in 2010–2011 and 2012–2013 (Table 5). Plant number was greater with CK than FSM in 2009–2010 and 2011–2012, but was greater with LSM or HSM than CK in 2010–2011 and 2012–2013. In 2013–2014 and 2014–2015, plant number was greater with FSM or HSM than other treatments. Tiller number was greater with HSM than CK in 2008–2009, 2010–2011, 2012–2013, and 2014–2015. In contrast, tiller number was greater with CK than HSM and FSM in 2009–2010 and 2011–2012. In 2013–2014, tiller number
2.4. Data analysis Data for soil water and wheat parameters were analyzed using the MIXED procedure of SAS (Littell et al., 1996). Mulching, year, and mulching × year interaction were considered as fixed effects and replication as the random effect. Means were separated by using the Fisher’s protected least significant difference test when treatments and interactions were significant. Unless otherwise stated, the differences among treatments and treatment × year interaction were considered significant at P ≤ 0.05. Relationship between WUE and PSE was analyzed using a regression (PROC REG) procedure.
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Table 3 Effect of wheat straw mulching on precipitation-storage efficiency (PSE) and winter wheat water-use efficiency (WUE) from 2008 to 2009 to 2014–2015. Treatment1 SWP (mm) CK LSM HSM FSM SWH (mm) CK LSM HSM FSM PSE (%) CK LSM HSM FSM ET (mm) CK LSM HSM FSM WUE (kg ha−1 mm−1) CK LSM HSM FSM
2008–2009
2009–2010
2010–2011
2011–2012
2012–2013
2013–2014
2014–2015
315 319 315 308
297 322 327 311
b a a ab
361 369 370 370
368 374 371 369
320 331 353 339
340 352 351 346
360 372 374 376
238 236 231 229
229 235 257 214
ab ab a b
259 256 259 261
265 263 273 265
253 261 271 257
251 259 268 256
290 300 311 281
– – – –
21.2 31.0 34.2 29.4
c ab a b
28.8 29.2 24.8 34.1
24.3 26.2 24.9 24.1
15.7 20.0 23.0 21.5
21.9 23.1 20.1 22.7
33.7 35.1 32.8 37.2
ab ab b a
239 245 245 241
263 282 265 292
312 320 307 315
220 224 235 236
333 337 327 335
356 359 350 382
ab ab b a
19.4 17.2 18.9 19.6
a b a a
17.4 17.6 18.7 16.9
b b b a
335 345 344 341 ab ab a b
16.4 14.6 13.1 14.1
a b b b
22.0 19.4 20.3 20.9
a b ab ab
24.6 22.8 21.6 22.3
c bc a ab
b a a a
a b b b
24.3 19.0 15.3 23.7
a b c a
b a a a
12.2 a 7.2 c 7.6 c 10.6 b
Numbers followed by different letters within a column are significantly different at P ≤ 0.05 by the least significance difference test. NS, not significant, ** and *** significant at p ≤ 0.01 and p ≤ 0.001 levels. 1 Treatments are CK, no mulching; FSM, wheat straw mulching at 9000 kg ha−1 during summer fallow; HSM, wheat straw mulching at 9000 kg ha−1 throughout the year; and LSM, wheat straw mulching at 4500 kg ha−1 throughout the year.
was greater with FSM than HSM in 2009–2010, 2010–2011, and 2011–2012, but greater with CK than other treatments in 2012–2013 and 2013–2014. Harvest index was lower with LSM than other treatments in 2008–2009. In 2009–2010, 2010–2011, and 2011–2012, harvest index was greater with CK than HSM. In 2012–2013, 2013–2014, and 2014–2015, harvest index was greater with CK and FSM than LSM and HSM. Averaged across years, seedling number was greater with CK than HSM (Table 4). Tiller and plant numbers were greater with LSM and HSM than CK and FSM, but the trend reversed for grain yield and harvest index. Spike number and thousand-grain weight were greater with FSM than other treatments. Aboveground biomass yield was greater with HSM than CK. Grain yield was not significantly different between CK and FSM, and they were greater than HSM and LSM. Among years, number of seedling, plant, tiller, and spike were, respectively, greater in 2008–2009, 2009–2010, 2010–2011, and
was greater with FSM than LSM and HSM. Spike number was greater with LSM and FSM than CK in 2008–2009 and 2009–2010. In 2010–2011 and 2011–2012, spike number was greater with LSM than other treatments. Spike number was greater with FSM than LSM and HSM in 2012–2013 and 2014–2015 and greater with HSM than LSM and FSM in 2013–2014. Aboveground biomass yield was greater with LSM or HSM than CK or FSM in 20008–2009, 2009–2010, 2010–2011, and 2012–2013 (Table 6). Biomass was greater with FSM than LSM in 2011–2012 and 2013–2014, but was greater with CK than other treatments in 2014–2015. Grain yield was lower with LSM in 2008–2009, but higher with CK in 2010–2011 than other treatments. In 2009–2010, grain yield was greater in LSM and HSM than CK. Grain yield was greater with CK and FSM than LSM and HSM in 2011–2012, 2013–2014, and 2014–2015. The 1000-grain weight was greater with LSM or HSM than other treatments in 2008–2009 and 2014–2015. The 1000-grain weight
Table 4 Effect of wheat straw mulching on number of winter wheat seedlings, plants, tillers, and spikes, thousand-grain weight, aboveground biomass and grain yields, and harvest index averaged across years. Treatment1
Seedling number (million ha−1)
Tiller number (plant−1)
Plant number (million ha−1)
Spike number (million ha−1)
Thousandgrain weight (g)
Aboveground biomass yield (Mg ha−1)
Grain yield (Mg ha−1)
Harvest index
CK LSM HSM FSM Significance Treatment Year Treatment × year
2.08 2.07 2.05 2.07
6.25 6.50 6.53 6.41
13.6 14.0 14.0 13.8
4.39 4.63 4.32 4.73
45.5 45.3 45.4 46.0
14.2 14.9 15.1 14.6
5.63 4.93 4.72 5.46
0.402 0.333 0.315 0.378
*** *** ***
a ab b ab
*** *** ***
c a a b
*** *** ***
b a a b
c b c a
*** *** ***
*** *** ***
b b b a
*** *** ***
b ab a ab
*** *** ***
a b b a
a b b a
*** *** ***
Numbers followed by different letters within a column are significantly different at P ≤ 0.05 by the least significance difference test. *** significant at p ≤ 0.001 levels. 1 Treatments are CK, no mulching; FSM, wheat straw mulching at 9000 kg ha−1 during summer fallow; HSM, wheat straw mulching at 9000 kg ha−1 throughout the year; and LSM, wheat straw mulching at 4500 kg ha−1 throughout the year. 98
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Table 5 Effect of wheat straw mulching on number of winter wheat seedling, plants, tiller and spikes from 2008 to 2009 to 2014–2015. Treatment1
2008–2009
2009–2010
2010–2011
2011–2012
2012–2013
2013–2014
2014–2015
2.34 2.33 2.31 2.37
ab bc c a
1.92 1.91 1.83 1.86
a a b b
2.07 2.03 2.04 2.08
ab b b a
2.07 2.08 2.05 2.04
ab a ab b
2.28 2.28 2.29 2.28
1.40 1.38 1.37 1.39
15.6 15.3 15.3 15.1
a ab ab b
12.7 14.3 13.8 13.8
c a b b
13.9 13.2 12.8 13.5
a b c b
12.5 13.0 13.0 12.7
b a a ab
15.3 15.1 14.9 15.7
b bc c a
11.9 13.9 14.3 12.7
d b a c
6.70 6.63 6.57 6.37
a ab b c
6.63 7.50 7.53 7.43
b a a a
6.70 6.53 6.30 6.50
a b c b
6.07 6.23 6.33 6.23
c b a b
6.73 6.60 6.53 6.90
ab bc c a
5.67 6.70 7.00 6.10
d b a c
4.46 4.75 4.81 4.83
b a a a
4.34 4.60 4.13 4.43
b a c b
5.00 5.14 4.76 4.90
b a d c
2.96 2.90 2.80 3.00
ab b c a
6.90 6.87 6.97 6.53
ab b a c
2.76 3.24 2.67 4.49
c b c a
−1
Seedling number (million ha ) CK 2.51 LSM 2.51 HSM 2.48 FSM 2.51 Plant number (million ha−1) CK 13.2 LSM 13.4 HSM 13.5 FSM 13.5 Tiller number (plant−1) CK 5.27 b LSM 5.33 ab HSM 5.47 a FSM 5.37 ab Spike number (million ha−1) CK 4.37 b LSM 4.91 a HSM 4.15 b FSM 4.96 a
Numbers followed by different letters within a column are significantly different at p ≤ 0.05 by the least significance difference test. 1 Treatments are CK, no mulching; FSM, wheat straw mulching at 9000 kg ha−1 during summer fallow; HSM, wheat straw mulching at 9000 kg ha−1 throughout the year; and LSM, wheat straw mulching at 4500 kg ha−1 throughout the year.
2013–2014 than other years (Table 5). Grain yield and aboveground biomass were greater in 2013–2104 and harvest index and thousandgrain weight were greater in 2011–2012 than other years.
were greater in 2012–2013 and 2013–2014 than other years (Table 3). The WUE decreased as PSE increased for all treatments, except for HSM (Fig. 1).
3.4. Evapotranspiration and water use efficiency
4. Discussion
The ET did not vary among treatments, but varied among years (Table 2). The WUE varied among treatments and years, with a significant treatment × year interaction. The WUE was lower with LSM in 2008–2009, but greater with CK in 2010–2011, 2012–2013, and 2014–15 than other treatments (Table 3). The WUE was greater with HSM than FSM in 2009–2010 and greater with CK than LSM in 2011–2012. In 2013–2014, WUE was greater with CK and FSM than LSM and HSM. Averaged across years, WUE was greater with CK than other treatments (Table 2). Averaged across treatments, ET and WUE
Straw mulching increased SWP by 3–4% and PSE by 8–16% compared with no mulching, and the effect was more obvious in below average precipitation years than above average precipitation years suggesting that straw mulching could be a good water conservation strategy for dry areas. Higher soil water storage with straw mulching may result from reducing evaporation by providing an insulation layer (Baumhardt and Jones, 2002) and lowering the daily soil temperature and/or from increasing rainfall infiltration and hydraulic conductivity during the summer period (Scott et al., 2010; Awe et al., 2015). Higher
Table 6 Effect of wheat straw mulching on winter wheat biomass and grain yields, harvest index, and thousand-grain weight from 2008 to 2009 to 2014–2015. Treatment1
2008–2009
2009–2010
2010–2011
2011–2012
2012–2013
2013–2014
2014–2015
4.60 4.98 4.93 4.91
b a a ab
5.47 5.02 4.50 4.78
a b c bc
6.87 6.22 6.23 6.57
a b b a
5.40 5.11 5.08 5.25
8.08 6.39 5.01 7.95
a b c a
4.36 2.58 2.66 4.05
a b b a
10.6 15.7 17.4 13.0
d b a c
13.0 13.0 13.5 12.0
b b a c
14.4 13.7 14.3 14.7
ab b ab a
12.8 14.2 14.7 13.2
22.4 21.3 20.5 23.6
b c c a
13.0 11.9 11.9 12.1
a b b b
−1
Grain yield (Mg ha ) CK 4.67 a LSM 4.23 b HSM 4.65 a FSM 4.73 a Aboveground biomass (Mg ha−1) CK 13.0 b LSM 14.3 a HSM 13.5 ab FSM 13.2 b Harvest index CK 0.359 a LSM 0.296 b HSM 0.343 a FSM 0.358 a Thousand-grain weight (g) CK 47.5 c LSM 49.7 a HSM 49.1 b FSM 49.4 b
0.437 0.317 0.282 0.377 43.6 43.1 42.4 45.2
a c d b
b c d a
0.421 0.388 0.332 0.398 48.7 45.7 45.1 49.2
a b c ab
0.476 0.454 0.437 0.448
b c d a
50.4 51.5 50.2 50.6
a ab b b
ab ab b a
b a a b
0.423 0.360 0.345 0.396 44.2 43.4 42.7 42.1
a b b a
a b c d
0.361 0.300 0.243 0.337 46.4 45.0 45.4 44.2
a b b c
a b c a
0.336 0.217 0.222 0.335 38.1 38.6 42.9 41.6
a b b a
d c a b
Numbers followed by different letters within a column are significantly different at p ≤ 0.05 by the least significance difference test. 1 Treatments are CK, no mulching; FSM, wheat straw mulching at 9000 kg ha−1 during summer fallow; HSM, wheat straw mulching at 9000 kg ha−1 throughout the year; and LSM, wheat straw mulching at 4500 kg ha−1 throughout the year. 99
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(Table 4), a result of increased soil water availability (Table 2). Such effects were pronounced more during the normal or dry years than the wet years (Tables 5 and 6). Straw mulching throughout the year (LSM and HSM) reduced wheat grain yield and harvest index at the cost of biomass yield compared with CK and FSM (Table 4). It is likely that increased soil water availability due to straw mulching throughout the year favored early biomass growth due to increased plant and tiller numbers but soil may not have stored enough moisture to continue yield formation. Studies show that water deficit in any period of winter wheat development can result in a substantial decline in the yield and efficiency with which soil water reserves are utilized (Verda et al., 2014). Besides, straw mulching also affects soil nutrient dynamics and thereby wheat yield (Lu et al., 2015). Although we did not measure soil N content, straw mulch applied at planting possibly immobilized soil inorganic N, thereby reducing N availability and grain yield. In southern Australia, Scott et al. (2010) found that the concentration of Nitrate-N in soil solution decreased as the rate of straw amount as mulch increased. Addition of crop residue with high C/N ratio, such as wheat straw, can reduce N availability to crops by increasing N immobilization (Lu et al., 2015). Gao et al. (2009) reported that straw mulching favored more wheat vegetative than reproductive growth compared with no mulching. Straw mulching during fallow, however, produced similar grain yield and harvest index compared with no mulching, suggesting that straw mulching is only beneficial when applied during the fallow period and that additional N fertilization may be needed to increase wheat grain yield when mulch is applied. The effectiveness of year-round straw mulching in increasing grain and biomass yields was evident during the dry years, such as in 2008–2009, 2009–2010, and 2012–2013, when grain and biomass yields were greater with HSM or LSM than other treatments (Tables 1 and 6). The trends reversed in the wet years. This suggests that straw mulching is beneficial in sustaining wheat yield only during dry periods. Several researchers (Chen et al., 2013; Lu et al., 2014, 2015) have reported that wheat straw mulching increased winter wheat yields compared with no mulching when soil water content is low. BalwinderSingh et al. (2011) found that mulching improved crop growth and yield attributes when water was limiting in northwest India, however this only led to significantly higher yield when there was prolonged water stress prior to anthesis. In a meta-analysis of the effect of straw mulching on soil water content and wheat yield, Wang et al. (2015) found that wheat straw mulching improved winter wheat yield compared with no mulching when annual precipitation was < 250 mm. Straw mulching during fallow or no mulching increased harvest index than other treatments in most years by enhancing grain yield relative to total biomass yield in this study. Although straw mulching increased SWP, it did not affect ET (Table 2), suggesting that wheat consumed similar amount of water, regardless of treatments. Greater amount of water may have used in early biomass growth leading to greater biomass in mulched treatments, but no difference in grain yield and reduced WUE with LSM and HSM compared with other treatments. Some researchers (Huang et al., 2005; Lenssen et al., 2014) have reported linear relationship between wheat grain yield and WUE. Our results, however, were in contrast to those reported for greater WUE with straw mulching than without in the semiarid areas (Deng et al., 2006; Chakraborty et al., 2010). Straw mulching reduced WUE compared with no mulching, specifically, during years with > 500 mm annual precipitation. Above-average growing season precipitation increased PSE, but reduced wheat growth and yield parameters as well as WUE in 2014–2015 than other years (Tables 1, 3, 5, and 6). Increased soil water recharge during the fallow increased PSE in 2014–2015. This, followed by increased precipitation during the growing season, resulted in anaerobic condition, which may have reduced wheat growth, yield, and WUE in 2014–2015. Straw mulching appears to be beneficial compared with no mulching for increasing PSE during the dry years, but not necessarily increase WUE
Fig. 1. Relationship between water use efficiency (WUE) and precipitation storage efficiency (PSE) under different treatments. Treatments are CK, no mulching; FSM, wheat straw mulching at 9000 kg ha−1 during summer fallow; HSM, wheat straw mulching at 9000 kg ha−1 throughout the year; and LSM, wheat straw mulching at 4500 kg ha−1 throughout the year. The solid, dot, dash and dash-dot lines were fitted for CK, LSM, FSM and HSM, respectively. The n.s. means the fitting was not significant.
rate of straw mulching conserved more soil water until crop harvest than mulching during fallow or no mulching, as shown by greater SWH with HSM than CK and FSM. This is in agreement with that reported by Stagnari et al. (2014) in a Mediterranean environment. Decomposition of wheat residue due to higher soil temperature and water content during fallow and shorter duration of mulching probably reduced the effectiveness of FSM to conserve soil water at wheat harvest in the present study. Only 24–28% of the total precipitation during summer fallow was stored in the soil (Table 2), a case similar to that reported by Wang et al. (2011) in the Loess Plateau of China. Straw mulching applied either at lower rate throughout the year or at higher rate during fallow was more effective in increasing PSE than no mulching, a result of reduced water loss due to evaporation. Baumhardt et al. (2013) also found that PSE was greater with wheat residue cover than without under cotton (Gossipium hirsutum L.) in the southern high plain of USA. Straw mulching during fallow period increased PSE during years with wet fallows. In contrast, year-round mulching, specifically HSM, increased PSE during years with a dry fallow, such as in 2009–2010 (Tables 1 and 3). However, increased PSE due to straw mulching did not improve WUE leading to low or no effects on wheat yield (Fig. 1). It is likely that some of the wheat straw used for mulching contributed to soil organic matter accumulation, and thereby increased SWP and PSE (Iqbal et al., 2011; Wang et al., 2011). It may take several years to see the effects of increased soil organic matter due to straw mulching to show difference in water use efficiency. Higher PSE with mulching generally resulted in greater soil water storage at planting (Table 2), which can enhance the germination and growth of wheat in dryland farming systems, but may not be enough to support yield formation and increase WUE (Deng et al., 2006). Increased SWP and PSE with LSM and HSM translated into enhanced wheat plant stand and tiller numbers (Tables 2 and 4), probably due to greater soil water availability for early growth of the crop. The lower seedling number with HSM appeared to be a result of death of some seedlings due to lower soil temperature at planting from high rate of mulching, a case similar to that observed by several researchers (Gao and Li 2005; Awe et al., 2015). This occurred, specifically, during years with dry growing season, such as 2009–2010 and 2012–2013 (Tables 1 and 5). Straw mulching during fallow (FSM) appeared to have a beneficial effect in increasing wheat spike number with heavier grains 100
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and wheat yield during years with > 500 mm annual precipitation. Wheat straw mulching could be a good strategy to mitigate drought impacts in drylands of Loess Plateau and similar agroecosystems.
FAO/Unesco, 1988. Soil Map of the World, Revised Legend. FAO, Rome. Gao, Y.J., Li, S.X., 2005. Cause and mechanism of crop yield reduction under straw mulch in dryland. Trans. CSAE 21, 15–19 in Chinese with English abstract. Gao, Y., Li, Y., Zhang, J., Liu, W., Dang, Z., Cao, W., Qiang, Q., 2009. Effects of mulch, N fertilizer, and plant density on wheat yield wheat nitrogen uptake, and residual soil nitrate in a dryland area of China. Nutr. Cycl. Agroecosyst. 85, 109–121. Huang, Y., Chen, L., Fu, B., Huang, Z., Gong, J., 2005. The wheat yields and water-use efficiency in the Loess Plateau: straw mulch and irrigation effects. Agric. Water Manage. 72, 209–222. Iqbal, M., Anwarul, H., Es, H.M.V., 2011. Influence of residue management and tillage systems on carbon sequestration and nitrogen phosphorus, and potassium dynamics of soil and wheat production in semi-arid region. Commun. Soil Sci. Plan. 42, 528–547. Jordán, A., Zavala, L.M., Gil, J., 2010. Effects of mulching on soil physical properties and runoff under semi-arid conditions in southern Spain. Catena 81, 77–85. Lenssen, A.W., Sainju, U.M., Iversen, W.M., Allen, B.L., Evans, R.G., 2014. Crop diversification, tillage, and management influences on spring wheat yield and soil water use. Agron. J. 106, 1445–1454. Li, S.X., Wang, Z.H., Li, S.Q., Gao, Y.J., Tian, X.H., 2013. Effect of plastic sheet mulch, wheat straw mulch, and maize growth on water loss by evaporation in dryland areas of China. Agric. Water Manage. 116, 39–49. Li, Y.S., 1983. The properties of water cycle in soil and their effect on water cycle for land in the Loess Plateau. Acta Ecol. Sin. 3, 91–101 In Chinese. Littell, R.C., Milliken, G.A., Stroup, W.W., Wolfinger, R.D., 1996. SAS System for Mixed Models. SAS Inst. Inc., Cary, NC. Liu, W., Zhang, X.C., Dang, T., Ouyang, Z., Li, Z., Wang, J., Wang, R., Gao, C., 2010. Soil water dynamics and deep soil recharge in a record wet year in the southern loess plateau of China. Agric. Water Manage 97, 1133–1138. Lu, X., Li, S., Bu, Q., Cheng, D., Duan, W., Sun, Z., 2014. Effects of rainfall harvesting and mulching on corn yield and water use in the corn belt of northeast China. Agron. J. 106, 2175–2184. Lu, X., Li, Z., Sun, Z., Bu, Q., 2015. Straw mulching reduces maize yield, water, and nitrogen use in northeastern China. Agron. J. 107, 406–414. Nielsen, D.W., Vigil, M.F., 2010. Precipitation storage efficiency during fallow in wheatfallow systems. Agron. J. 10, 537–543. Scott, B.J., Eberbach, P.L., Evans, J., Wade, L.J., 2010. In: Clayton, E.H., Burns, H.M. (Eds.), EH Graham Centre Monograph No. 1: Stubble Retention in Cropping Systems in Southern Australia: Benefits and Challenges. Industry & Investment NSW, Orange. Sharma, P., Abrol, V., Sharma, R.K., 2011. Impact of tillage and mulch management on economics energy requirement and crop performance in maize-wheat rotation in rainfed subhumid inceptisols, India. Eur. J. Agron. 34, 46–51. Stagnari, F., Galieni, A., Speca, S., Cafiero, G., Pisante, M., 2014. Effects of straw mulch on growth and yield of durum wheat during transition to Conservation Agriculture in Mediterranean environment. Field Crop. Res. 167, 51–63. Su, Z., Zhang, J., Wu, W., Cai, D., Lv, J., Jiang, G., Huang, J., Gao, J., Hartmann, R., Gabriels, D., 2007. Effects of conservation tillage practices on winter wheat water-use efficiency and crop yield on the Loess Plateau. China. Agric. Water Manage. 87, 307–314. Tolk, J.A., Howell, T.A., Evett, S.R., 1999. Effect of mulch, irrigation, and soil type on water use and yield of maize. Soil Till. Res. 50, 137–147. Verda, B., Vida, G., Verda-Laszlo Bencze, S., Veisz, O., 2014. Effect of simulating drought in various phenophases on the water use efficiency of winter wheat. J. Agron Crop Sci. 201, 1–9. Wang, L., Shangguan, Z., 2015. Water–use efficiency of dryland wheat in response to mulching and tillage practices on the Loess Plateau. Sci. Rep. 5, 12225. Wang, J., Liu, W., Dang, T., 2011. Responses of soil water balance and precipitation storage efficiency to increased fertilizer application in winter wheat. Plant Soil 347, 41–51. Wang, X., Wu, H., Dai, K., Zhang, D., Feng, Z., Zhao, Q., Wu, X., Jin, K., Cai, D., Oenema, O., Hoogmoed, W.B., 2012. Tillage and crop residue effects on rainfed wheat and maize production in northern China. Field Crop. Res. 132, 106–116. Wang, J., Liu, W.Z., Dang, T.H., Sainju, U.M., 2013. Nitrogen fertilization effect on soil water and wheat yield in the Chinese Loess Plateau. Agron. J. 105, 143–149. Wang, L., Chen, J., Shangguan, Z., 2015. Yield responses of wheat to mulching practices in dryland farming on the loess plateau. PLoS One 10, e0127402. Wang, X., Jiao, F., Li, X., An, S., 2017. The loess plateau. In: Zhang, L., Schwarzel, K. (Eds.), Multifunctional Land-Use Systems for Managing the Nexus of Environmental Resources. United Nations University, Dresden, Germany, pp. 11–27. Xing, N.Q., Zhang, Y.Q., Wang, L.X., 2001. The Study on Dryland Agriculture in North China. Chinese Agriculture Press, Beijing. Zhang, P., Wei, T., Wang, H., Wang, M., Meng, X., Mou, S., Zhang, R., Jia, Z., Han, Q., 2015. Effects of straw mulch on soil water and winter wheat production in dryland farming. Sci. Rep. 5, 10725.
5. Conclusions Wheat straw mulching increased SWP, PSE, winter wheat seedling growth, plant, and tiller numbers compared with no mulching in the semiarid Loess Plateau of China. Mulching throughout the year, however, reduced spike number, grain yield, thousand-grain weight, harvest index, and water-use efficiency at the expense of aboveground biomass yield, but mulching during summer fallow maintained grain yield compared with no mulching. Mulching rate had little effect on soil water storage and wheat characteristics. Further study may confirm the benefit of straw mulching on N fertilization and SOC accrual, this revealed benefit of straw mulching on precipitation storage and wheat yield compared with no mulching, specifically during the dry years. It did not increase WUE and wheat yield during years with > 500 mm annual precipitation. Because of increased precipitation storage efficiency and similar wheat yields, straw mulching should be applied during fallow period or at low rate throughout the year in dry years to increase soil water conservation and improve agricultural sustainability in drylands. Acknowledgements This work was supported by the National Natural Science Foundation of China (grant numbers 31570440, 31270484) and the International Scientific and Technological Cooperation and Exchange Project of Shaanxi Province, China (grant number 2015KW-026). References Awe, G.O., Reichert, J.M., Wendroth, O.O., 2015. Temporal variability and covariance structures of soil temperature in a sugarcane field under different management practices in southern Brazil. Soil Till. Res. 150, 93–106. Balwinder-Singh, Eberbach, P.I., Humphreys, E., Kukal, S.S., 2011. The effect of rice straw mulch on evapotranspiration, transpiration, and soil evaporation of irrigated wheat in Punjab, India. Agric. Water Manage. 98, 1847–1855. Baumhardt, R.L., Jones, O.R., 2002. Residue management and tillage effects on soil-water storage and grain yield of dryland wheat and sorghum for a clay loam in Texas. Soil Till. Res. 68, 71–82. Baumhardt, R.L., Schwartz, R., Howell, T., Evett, S.R., Colaizzi, P., 2013. Residue management effects on water use and yield of deficit irrigated cotton. Agron. J. 105, 1026–1034. Chakraborty, D., Nagarajan, S., Aggarwal, P., Gupta, V.K., Tomar, R.K., Garg, R.N., Sahoo, R.N., Sarkar, A., Chopra, U.K., Sarma, K.S.S., Kalra, N., 2008. Effect of mulching on soil and plant water status: and the growth and yield of wheat (Triticum aestivum L.) in a semi-arid environment. Agric. Water Manage. 95, 1323–1334. Chakraborty, D., Garg, R.N., Tomar, R.K., Singh, R., Sharma, S.K., Singh, R.K., Trivedi, S.M., Mittal, R.B., Sharma, P.K., Kamble, K.H., 2010. Synthetic and organic mulching and nitrogen effect on winter wheat (Triticum aestivum L.) in a semi-arid environment. Agric. Water Manage. 97, 738–748. Chen, H.Q., Hou, R.X., Gong, Y.S., Li, H.W., Fan, M.S., Kuzyakov, K., 2009. Effects of 11 years of conservation tillage on soil organic matter fractions in wheat monoculture in Loess Plateau of China. Soil Till. Res. 106, 85–94. Chen, S.Y., Zhang, X.Y., Sun, H.Y., Shao, L.W., 2013. Cause and mechanism of winter wheat yield reduction under straw mulch in the North China Plain. Chin. J. EcoAgric. 21, 519–525 in Chinese with English Abstract. Cook, H.F., Valdes, G.S., Lee, H.C., 2006. Mulch effects on rainfall interception, soil physical characteristics and temperature under Zea mays L. Soil Till. Res. 91, 227–235. Deng, X.P., Shan, L., Zhang, H., Turner, N.C., 2006. Improving agricultural water use efficiency in arid and semiarid areas of China. Agric. Water Manage. 80, 23–40.
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