Evaluating effects of four controlling methods in bare strips on soil temperature, water, and salt accumulation under film-mulched drip irrigation

Field Crops Research 214 (2017) 350–358

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Evaluating effects of four controlling methods in bare strips on soil temperature, water, and salt accumulation under film-mulched drip irrigation

MARK

⁎

Shuai Tana, Quanjiu Wanga,b, , Di Xua, Jihong Zhanga, Yuyang Shana a

State Key Laboratory Base of Eco-Hydraulic Engineering in Arid Area, Xi’an University of Technology, Xi’an, 710048, China State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A & F University, 712100, Yangling, China

b

A R T I C L E I N F O

A B S T R A C T

Keywords: Controlling method Soil temperature Soil water Salt accumulation Water-use efficiency

Film-mulched drip irrigation as an effective water saving irrigation method has been widely utilized in arid areas. Unnecessary soil-water loss and excessive salt accumulation from soil evaporation, however, still occur in the bare strips between adjacent films under drip irrigation so that developing a useful method to combat this has been a challenge. Applying the methods of soil evaporation control in the bare strips under film-mulched drip irrigation may alleviate this problem. In 2013 and 2014, we thus adopted four controlling methods (STM: straw mulching, SAM: sand mulching, PAM: polyacrylamide amendment application, and CSS: surface soil compaction) in bare strips to evaluate their effects on soil properties and cotton productivity under film-mulched drip irrigation in southern Xinjiang, northwestern China. The main results showed that the four controlling methods gave more stable daily soil temperatures in bare strips with respect to CK. In general, STM and PAM reduced the soil temperature while CSS and SAM increased it. Moreover, the four controlling methods effectively reduced daily soil evaporation by 34.6–96.2% and 61.1–77.3% in 2013 and 2014, respectively. Lower evapotranspiration was found in the four controlling methods. The salt accumulation amount from late seedling stage to harvest reduced greatly in the four controlling methods, especially in STM and PAM. There were no significant differences in cotton yield and water-use efficiency (WUE), but the WUE for the four controlling methods slightly increased by 10.2–12.2% and 1.1–8.5% in 2013 and 2014, respectively, with respect to CK. The highest yield and WUE were found in SAM during the both seasons, indicating that SAM could be more effective than the other controlling methods at the experimental site. The controlling methods in bare strips under film-mulched drip irrigation can provide an alternative option to prevent the risk of soil salinization and enhance crop productivity in the arid regions of Xinjiang and other similar regions in the world. However, long-term use of the controlling methods in bare strips under film-mulched drip irrigation should be further evaluated.

1. Introduction

accumulation from soil evaporation, however, have taken place in the bare strips which are arranged between adjacent films to allow for soil aeration and transmission of light as well as to avoid high soil temperature stress for crop growth. Therefore, developing a useful method to control the soil evaporation in the bare strips has been a challenging. Some studies have indicated that different controlling methods, such as straw or sand mulching surface soil, chemical amendments application, and surface soil compaction, can successfully control soil evaporation. Straw mulching as a common method can significantly reduce soil evaporation by decreasing the exchange of water vapor between soil surface and atmosphere (Huang et al., 2005). It can thus alter the water balance between soil evaporation and plant

Water shortage and soil salinization are two key factors limiting sustainable development of agriculture in arid areas (Li et al., 2016) so that it has forced producers of dryland crops (e.g. cotton) to ensure a favorable soil-water/salt environment in root zone for crop growth (Ji and Unger, 2001). In recent years, the technique of film-mulched drip irrigation combining the benefits of drip irrigation and film mulching has been widely used in arid areas to effectively moderate soil evaporation, prevent the risk of soil degradation, and increase water-use efficiency (WUE) and crop yields (Díaz-Pérez et al., 2005; Miles et al., 2012; Ning et al., 2015; Yang et al., 2016). Water loss and salt

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Corresponding author at: State Key Laboratory Base of Eco-Hydraulic Engineering in Arid Area, Xi’an University of Technology, Xi’an, 710048, China. E-mail address: [email protected] (Q. Wang).

http://dx.doi.org/10.1016/j.fcr.2017.09.004 Received 16 August 2017; Accepted 5 September 2017 0378-4290/ © 2017 Elsevier B.V. All rights reserved.

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transpiration, modify microclimate (e.g., temperature and microbial biomass) (Gupta and Gupta, 1985; Gupta and Acharya, 1993; Kumar and Goh, 1999), and moderate the salt accumulation in root zone (Pang et al., 2010; Zhao et al., 2014; Zribi et al., 2015). Sand mulching is another approach to controlling soil evaporation. This practice can decrease soil evaporation by 10–20% compared with no mulch (Modaihsh et al., 1985; Gale et al., 1993), control the soil salinity in root zone, and improve the management of insect pests (Davenport and Schiffhauer, 2000). Soil compaction can change the continuity and tortuosity of soil so that it may further affect soil water availability, heat fluxes, penetration resistance, and aeration (Hartmann et al., 2012; Schjønning et al., 2013; Siczek et al., 2015). At a proper range of compaction, it can increase soil retention and soil water availability (Warkentin, 1971; Sharma and Bhagat, 1993), and WUE (Sharma et al., 1995). Applying chemical materials is also an effective way to restrain soil evaporation, particularly for polyacrylamide application. Polyacrylamide can promote the ability of porous soils, especially in sandy soils, to store water (Sivapalan, 2006). The practice can also delay wilting where soil evaporation is intense and control or minimize the adverse impacts of salinity (Yang et al., 2014; Al-Uzairy, 2015). When the controlling methods are applied to the bare strips between adjacent films, it may be helpful in reducing invalid water loss and salt accumulation from soil evaporation, enhancing WUE, as well as achieving a more profitable crop yield under film-mulched drip irrigation. Moreover, the controlling methods may further affect the distributions of water, salinity, and temperature in soil which are complex and difficult to predict. Therefore, a two-year experiment was conducted in cotton field to evaluate the effects of four controlling methods (straw mulching, polyacrylamide application, surface soil compaction, and sand mulching) in bare strips on soil properties (i.e. soil temperature, water, salinity) and cotton productivity (i.e. cotton yield, aboveground biomass and WUE) under film-mulched drip irrigation in southern Xinjiang, northwestern China.

the mid-June and ended in the early September during the two seasons. The field was irrigated 11 and 12 times in 2013 and 2014, respectively. The total amounts of applied water, recorded by water meters with a precision of 0.001 m3, were 457.5 mm and 495 mm in 2013 and 2014, respectively. The irrigation water was extracted from the Kongque River with a salinity of 0.75 g L−1 (fresh water) in 2013 and from groundwater with a salinity of 2.01 g L−1 in 2014 (brackish water). Inorganic fertilizers (225 kg ha−1 urea with 46.4% N, 375 kg ha−1 diammonium phosphate with 46% P2O5 and 18% N, and 300 kg ha−1 potassium sulphate with 45% K2O) were applied before sowing. At squaring and flowering stages, 600 kg ha−1 urea, 98 kg ha−1 diammonium phosphate, and 88 kg ha−1 potassium sulphate was applied. Herbicides were used before planting, pesticides were applied every 5–7 days from seedling stage to boll stage with a sprayer pump, and topping was conducted manually at the end of July.

2. Materials and methods

2.4. Data collection and calculations

2.1. Experimental site description

2.4.1. Meteorological data A Davis wireless Vantage Pro2 weather station (Davis Instruments, Hayward, USA) was installed about 30 m away from the experiment field to automatically collect meteorological data, such as rainfall, solar radiation, maximum and minimum air temperature, relative humidity, and wind speed at a height of 2 m. Daily reference crop evapotranspiration (ETo) calculated using the Penman-Monteith equation (Allen et al., 1998) during 2013 and 2014 seasons are displayed in Fig. 2. The irrigation amount in 2014 (495 mm) was thus higher than that in 2013 (457.5 mm) due to similar ETo (578.9 mm in 2013 and 584.5 mm in 2014), lower rainfall (60.1 mm in 2013 and 23.3 mm in 2014), and brackish irrigation water during the growing season for cotton in 2014.

2.3. Experimental setup The experiment was performed at late seedling stage (16 June 2013 and 14 June 2014) to ensure good seed emergence for all plots. Four controlling methods and an untreated control (CK) were applied to bare strips. The four controlling methods were: (1) STM, the bare strips were uniformly mulched with air-dried cotton straw with 20–30 cm length at a rate of 16.5 t ha−1 (nearly complete coverage); (2) CSS, the topsoil of bare strips was compacted by using a concrete plank (30-cm width, 20cm length, and 4-cm thickness, about 10 kg) and the bulk density of the 0–20 cm layer increased from 1.55 to 1.68 g cm−3; (3) PAM, the bare strips were uniformly applied with polyacrylamide solution at a rate of 42 kg ha−1; (4) SAM, the bare strips were uniformly mulched with airdried 1–2 mm sand at a rate of 240 t ha−1 (about 1.5-cm thickness). All treatments were arranged in a randomized block designed with three replicates. Each plot was 7 × 7 m and adjacent plots were separated by 1 m to eliminate the effect of the lateral movement of soil water.

The field experiment was conducted at Bazhou Irrigation Experimental Station (41°35′N, 86°09′E, and 901 m a.s.l.) in the Tarim Basin of Xinjiang of northwestern China, during 2013 and 2014 seasons. The site is representative of continental desert climate with a longterm annual precipitation of 58 mm and an average potential evaporation of 2788.2 mm (Wang et al., 2014; Li et al., 2015), making irrigation necessary for crop growth. The predominant soil texture at the site was a silt loam with a texture of 41.4% sand, 54.4% silt, and 4.2% clay according to the United States Department of Agriculture soil taxonomy. The average bulk density and field capacity of 1-m soil profile were 1.56 g cm−3 and 0.25 cm3 cm−3, respectively. The soil salt content of the field in 1-m soil profile varied from 3.24 to 13.5 g kg−1, indicating slight to moderate salinity. The average groundwater table was deeper than 5 m during the two seasons.

2.4.2. Soil temperature and evaporation measurements Soil temperature in the bare strips for each plot was measured with soil thermometers (Hongxing Thermal Instruments, Wuqiang County, Hebei Province, China) from 5 to 20 cm at 5-cm intervals and recorded daily at 8:00 and 20:00 to calculate daily soil temperature of 20-cm soil profile. Soil evaporation in the bare strips for each plot was monitored daily at 20:00 with microlysimeters (12.5-cm diameter, 20-cm length, and 1.8-mm wall thickness). Details of the microlysimeter arrangement can be found elsewhere (e.g., Hernández et al., 2015; Vial et al., 2015; Wang et al., 2015).

2.2. Cotton cultivation and irrigation management Cotton (Gossypium hirsutum L.) was sown after plowing on 26 April 2013 and 3 May 2014 at a density of 22 seeds m−2. The planting pattern and drip lines arrangement in the field followed the local practice of “one film, two drip lines and four rows” (Fig. 1). Four rows of cotton were covered by one white plastic film of 110-cm width and irrigated with two drip lines with emitter intervals of 30 cm and a discharge rate of 2.0 L h−1. The width of the bare strip between a pair of mulches was 30 cm. There was no irrigation at seedling stage (from early May to mid-June) because of a flood irrigation about 300 mm with a salinity of 0.8 dS m−1 in mid-April each year. The irrigation schemes during the both growing seasons are illustrated in Fig. 2. The irrigation began in

2.4.3. Soil-water content and salinity Soil samples were collected to determine soil-water content (SWC) and salinity at a 10-cm interval from 0 to 40 cm and at a 20-cm interval from 40 to 100 cm by using an auger with 5-cm diameter in the middle of wide, narrow, and bare strips. The samples were collected at the late 351

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Fig 1. Daily reference crop evapotranspiration (ETo), rainfall, and irrigation at the experimental site during (a) 2013 and (b) 2014 seasons.

main growth stages for cotton (seedling, squaring, flower-boll stage) one day before irrigation and harvest. All auger holes were refilled with soil to minimize the experimental error after each sampling. The soil samples were weighed, dried in a fan-assisted oven at 105 ± 2 °C for 24 h, and reweighed to determine the gravimetric SWC. Volumetric SWC was then obtained by multiplying the gravimetric SWC with the average soil bulk density of 1-m soil profile. A DDS-307A conductivity meter (Shanghai Precision & Scientific Instrument Inc., Shanghai, China) was used to measure the electrical conductivity at a 1:5 soil:water extract (EC1:5) at 25 °C. The value of EC1:5 for each soil sample can be converted into soil salt content (SC, g kg−1) based on a linear relationship (SC = 4.25 EC1:5; r2 = 0.987; n = 26).

aboveground biomass and harvest index (HI, the ratio of aboveground biomass to cotton yield). 2.5. Calculations and analysis methods 2.5.1. Evapotranspiration calculation Evapotranspiration (ET) was calculated based on the water-balance equation (Hussain and Al-Jaloud, 1998; Sun et al., 2006): ET = P + I − D ± ΔW

(1)

where P is the rainfall (mm), I is the irrigation amount (mm), D is the amount of downward drainage out of 1-m soil profile (mm), and ΔW is the variation in the amount of water storage in 1-m soil profile (mm). The effects of groundwater and runoff were negligible because of the deep groundwater table (> 5 m) and drip irrigation. D was calculated from field capacity (θFC, cm3 cm−3), irrigation amount (I), and soil-water storage (SWS, mm) in 1-m soil profile one day before irrigation (Eq. (2)). There were deficient data of SWS for

2.4.4. Aboveground biomass and yield measurement At harvest, cotton yield (seeds and lint) was obtained from a 6.67m2 area for each plot on 7 and 15 September 2013 and 2014, respectively. Three plants from each plot were randomly collected, cut, and oven-dried at 70 °C until they reached a constant weight to determine

Fig. 2. Planting and drip-line arrangements in the experimental plot.

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each irrigation so that the average SWS during the growing seasons was used to replace it. The D was given as: D = P + I + SWS − 1000θFC

Table 1 Statistical analyses of daily soil temperature for the four controlling methods and CK in 20-cm soil profile in bare strips during the irrigation periods in 2013 (16–21 July) and 2014 (16–21 July).

(2)

If D > 0, it means that drainage occurs in 1-m soil profile. If D < 0, there is no drainage in 1-m soil profile. Weights were assigned as proportions of the strip widths at different locations, and ΔW was calculated as:

3 1 2 Δ W= 1000( Δθ bare + Δθnarrow + Δθwide) 14 2 7

Treatment Average (ºC)

(3)

2.5.2. Salt accumulation calculation Salt accumulation amount from the late seedling stage to harvest during the both seasons was obtained as:

3 1 2 ΔSCbare + ΔSCnarrow + ΔSC wide) 14 2 7

CV (%)

Average (°C)

S.D. (°C)

CV (%)

5.9 10.4 8.3 11.4 11.8

26.2 ab 27.2 a 23.7 c 26.9 a 25.0 b

2.0 3.2 2.5 2.7 3.6

7.5 11.9 10.5 10.1 14.4

*** *** ***

(4) significant difference in daily soil temperature between STM and CK. PAM had the lowest daily soil temperature of 23.7 °C. CSS and SAM dramatically increased daily soil temperature with respect to CK. 3.2. Soil evaporation Similar changes in cumulative soil evaporation for all treatments in bare strips were found during the both irrigation periods (Fig. 3). All controlling methods had lower cumulative soil evaporations than CK. Lower daily soil evaporations were recorded in 2014 even though under different controlling methods, because of lower soil temperature (Table 1) from lower air temperature during the irrigation period. Another possible reason was the lower water potential gradient between soil and atmosphere from the lower osmotic potential with brackish water irrigation in 2014. The daily soil evaporation for the four controlling methods were much lower than that for CK (p < 0.05, Table 2). The reductions in soil evaporation for the four controlling methods varied from 34.6 to 96.2% and 61.1 to 77.3% in 2013 and 2014, respectively. The lowest daily soil evaporationwas measured in STM (0.38 mm day−1) in 2013 and SAM (0.65 mm day−1) in 2014. It also was noted that there were no significant differences in soil evaporation among the four controlling methods except for CSS in 2013, suggesting that the four controlling methods may have same effects on soil evaporation.

2.5.3. WUE calculation WUE (kg m−3) for all treatments was calculated as (Sun et al., 2012):

100Y ETtotal

2014

Different letters within a column indicate significant differences at p < 0.05. ***p < 0.001. S.D. represents standard deviation. NS represents no significance. STM: straw mulching; CSS: surface soil compaction; PAM: polyacrylamide amendment application; SAM: sand mulching; CK: untreated control.

where ΔS is the amount of salt accumulation amount in 1-m soil profile (g m−2); Si and Sf are the soil salt amount at late seedling stage and harvest in 1-m soil profile (g m−2), respectively; ρs is the average bulk density of 1-m soil profile (g cm−3); ΔSCbare, ΔSCnarrow, and ΔSCwide are the differences in soil salt content for the bare, narrow and wide soil strips between late seedling stage and harvest in 1-m soil profile (g kg−1), respectively.

WUE =

S.D. (°C)

STM 25.9 c 1.5 CSS 29.4 ab 3.1 PAM 27.6 bc 2.3 SAM 29.3 ab 3.3 CK 29.8 a 3.5 Significance Treatment Year Treatment × Year

where Δθbare, Δθnarrow, and Δθwide are the differences in volumetric SWCs for the bare, narrow and wide soil strips between late seedling stage and harvest in 1-m soil profile (cm3 cm−3), respectively.

Δ S= Sf − Si = 1000ρs [(

2013

(5) −1

where Y is the cotton yield at harvest (t ha ) and ETtotal is the total evapotranspiration (mm) during the entire growing season. 2.5.4. Statistical methods A SPSS (Statistical Product and Service Solutions) software (version 21.0, IBM Corporation, USA) were used to conduct statistical analyses. The soil temperature, evaporation, SWS, soil salt amount, and cotton productivity were analyzed for average and standard deviation for each treatment (n = 3). The analysis of variance was used to compare the average for each treatment. The least significant differences were adopted to detect differences in the average among all treatments.

3.3. SWS and water balance 3. Results It has been reported that 85% cotton root were distributed in 30 − 50 cm topsoil under film-mulched drip irrigation (Hu et al., 2009; Kang et al., 2012; Chen et al., 2017). The 40-cm soil layer was thus considered to be the main root zone for cotton. To better understand the effect of the four controlling methods on soil water, the average SWSs for the controlling methods in main root zone were analyzed (Fig. 4). At late seedling stage, significant differences among all treatments (p < 0.05) were found in the initial SWS in main root zone during the both seasons, with a consequent impact on the average SWS. The possible reason could be the spatial variability of soil. Compared to the initial SWS in main root zone, the average SWSs for STM, CSS, and PAM increased during the two seasons, revealing that the three controlling methods could retain more water in soil with film-mulched drip irrigation. As for SAM and CK, the average SWSs were lower than the initial SWSs during 2013 and 2014 seasons. It is possibly due to more transpiration for cotton in SAM and more soil evaporation in CK according to the above results of soil evaporation for different controlling methods.

3.1. Soil temperature An irrigation period (13–19 July 2013 and 16–21 July 2014) was chosen for monitoring soil temperature and evaporation because of approximately 70 − 80% canopy cover and stable air temperature. Controlling methods had significant effects on daily soil temperature of 20-cm soil profile in bare strips (p < 0.05, Table 1). Coefficients of variation (CVs) for daily soil temperature for all controlling methods were lower than that for CK during the irrigation period, especially in 2013, indicating that the four controlling methods could stabilize soil temperature. The lowest CV was obtained in STM during the both seasons. The daily soil temperatures for all treatments in 2013 were much higher than those in 2014 (p < 0.001), which was likely due to higher air temperature during the irrigation period in 2013. In 2013, STM and PAM clearly reduced daily soil temperature in comparison with CK (29.8 °C) by 3.9 and 2.3 °C (p < 0.05), respectively, while CSS and SAM had no significant effects on it. In 2014, there was no 353

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Fig. 3. Cumulative soil evaporations for the four controlling methods and CK in bare strips during irrigation periods in (a) 2013 (13–19 July) and (b) 2014 (16–21 July). STM: straw mulching; CSS: surface soil compaction; PAM: polyacrylamide amendment application; SAM: sand mulching; CK: untreated control. The error bars represent standard deviations.

methods in ETb−h were found. The ranking of the treatment effect on ETb−h was in an order of CK > SAM > CSS > PAM > STM. In 2014, there were no significant differences (p > 0.05) among all treatments in ETb−h and the lowest ETb−h was found in CSS which was 4.9% lower than that in CK.

Table 2 Statistical analyses of daily soil evaporation for the four controlling methods and CK in 20-cm depth in bare strips during the irrigation periods in 2013 (13–19 July) and 2014 (16–21 July). Treatment

STM CSS PAM SAM CK Significance

2013

2014

Average (mm day−1)

Reduction relative to CK (%)

0.13 c 2.19 b 0.76 c 0.38 c 3.35 a

96.2 34.6 77.5 88.7 –

Treatment Year Treatment × Year

Average (mm day−1)

0.97 1.12 0.76 0.65 2.87

Reduction relative to CK (%)

b b b b a

3.4. Salt accumulation At late seedling stage, significant differences (p < 0.05) were found in the initial salt amount (Si) in the 40-cm and 1-m soil profiles at different locations (bare and mulched strips, and whole domain) among all treatments during the both seasons (Table 4). Like the initial SWS, the reason for the differences could be the soil spatial variability. To avoid the influences of Si and better evaluate the effects of the four controlling methods on soil salinity, the salt accumulation amount from late seedling stage to harvest (ΔS) were analyzed (Table 4). Controlling methods and locations significantly affected soil salinity (p < 0.05). The four controlling methods decreased ΔS greatly by 40.3–116.6% for 40-cm soil profile and 20.2–92.8% for 1-m soil profile in bare strips during the both years in comparison with CK (p < 0.05). The ΔS in the bare strips for all treatments were larger than zero apart from PAM in 2013, indicating that there has been salt accumulation for all treatments in the bare strips but the controlling methods could effectively delay the salt accumulation from soil evaporation. As to the mulched strips, there were also significant differences in ΔS (p < 0.05) among all treatments and the ΔS for all treatments were almost lower than zero in the 40-cm and 1-m soil profiles during the two seasons, revealing soil salt was leached by irrigation water in the film-mulched area, even though brackish water was used for irrigation in 2014. PAM had the lowest ΔS in the mulched strips in 40-cm and 1-m soil profiles. As for the whole domain, significant differences among all treatments were also found in ΔS (p < 0.05). The ΔS for the four controlling methods

66.0 61.1 73.4 77.3 – *** NS ***

Different letters within a column indicate significant differences among all treatments at p < 0.05. *** p < 0.001. NS represents no significance. STM: straw mulching; CSS: surface soil compaction; PAM: polyacrylamide amendment application; SAM: sand mulching; CK: untreated control.

There were significant differences (p < 0.05) in the initial SWS for all treatments so that the changes in average SWS for all treatments could not better represent the effect of controlling methods on soil water. The ET from late seedling to harvest (ETb−h) were thus analyzed (Table 3). The ETb-h in 2014 (498.1–523.7 mm) were lower than that in 2013 (530.8–567.5 mm) likely due to the poor cotton growth caused by brackish water irrigation. The four controlling methods greatly decreased (p < 0.05) ETb−h by 5.4–6.5% in 2013 in comparison with CK and no significant (p > 0.05) differences among the four controlling

Fig. 4. The initial and average SWSs for the four controlling methods and CK in 40-cm depth during (a) 2013 and (b) 2014 seasons. STM: straw mulching; CSS: surface soil compaction; PAM: polyacrylamide amendment application; SAM: sand mulching; CK: untreated control. The error bars represent standard deviations. Different letters within a column indicate significant differences among all treatments at p < 0.05.

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Table 3 Water balances for the four controlling methods and CK in 1-m soil profile during 2013 and 2014 seasons. Year

Treatment

Initial SWS (mm)

Final SWS (mm)

Drainage (mm)

Rainfall (mm)

I (mm)

ETb-h (mm)

2013

STM CSS PAM SAM CK STM CSS PAM SAM CK

160.4 bc 99.9 d 182.2 b 145.6 c 211.0 a 79.3 d 115.8 c 225.2 a 85.6 d 198.1 b

147.2 b 85.0 d 168.4 a 126.3 c 161.1 a 74.8 d 136.1 c 216.1 a 83.2 d 192.8 b

0.0 0.0 0.0 0.0 0.0 0.0 0.0 16.3 0.0 0.0

60.1 60.1 60.1 60.1 60.1 23.3 23.3 23.3 23.3 23.3

457.5 457.5 457.5 457.5 457.5 495.0 495.0 495.0 495.0 495.0

530.8 b 532.5 b 531.4 b 537.0 b 567.5 a 522.8 a 498.1 b 511.1 ab 520.7 ab 523.7 a

***

*** *** ***

*** NS –

– – –

– – –

– – NS

** NS NS

2014

Significance Treatment Year Treatment × Year

Different letters within a column indicate significant differences among all treatments at p < 0.05. **p < 0.01 and ***p < 0.001. NS represents no significance. STM: straw mulching; CSS: surface soil compaction; PAM: polyacrylamide amendment application; SAM: sand mulching; CK: untreated control.

3.5. Aboveground biomass and yield

were much lower than that for CK in 40-cm and 1-m soil profiles during the both seasons except for CSS and SAM in 40-cm soil profile during 2014 season. The main order of ΔS for the whole domain in the 1-m soil profile during the both seasons was: CK > CSS > SAM > STM > PAM.

At harvest, no significant differences (p > 0.05) were found in cotton yield and HI among all treatments in the two years (Table 5). SAM had the highest cotton yield of 6.40 t ha−1 in 2013 and 5.85 t ha−1 in 2014, which were 5.5% and 7.9% higher than that for CK

Table 4 Soil salt accumulations (ΔS) for the four controlling methods and CK in the bare strip, mulched strip, and whole domain in 40-cm and 1-m soil profiles in 2013 and 2014. Year

2013

Location

Bare strip

Mulched strip

Whole domain

2014

Bare strip

Mulched strip

Whole domain

Treatment

STM CSS PAM SAM CK STM CSS PAM SAM CK STM CSS PAM SAM CK STM CSS PAM SAM CK STM CSS PAM SAM CK STM CSS PAM SAM CK

40-cm soil profile

1-m soil profile

Si(g cm−2)

ΔS(g cm−2)

Si(g cm−2)

ΔS(g cm−2)

2821.1 bc 3925.0 b 5091.8 a 1879.6 c 5459.8 a 2478.1 b 3295.7 b 5427.0 a 1233.8 c 5427.0 a 2551.6 b 3430.6 b 5355.2 a 1372.2 c 5434.0 a 4747.1 b 5045.4 a 3845.4 b 1163.6 c 6099.6 a 4194.7 b 5377.1 a 3693.5 b 618.4 c 4982.5 ab 4313.1 ab 5306 a 3726.1 b 735.2 c 5221.8 a

232.1 c 64.1 c −348.1 d 507.2 b 2095.1 a −686.0 c 98.9 a −2171.2 d −667.2 c −214.6 b −489.3 b 91.4 a −1780.5 c −15.6 b 280.4 a 331.5 c 570.2 b 570.2 b 407.8 bc 954.7 a −584.3 b 219.9 a −1522.2 c 29.5 a −506.9 b −388.1 d 294.9 a −1073.8 e 110.6 b −193.7 c

3629.9 b 4269.7 b 11602.5 a 2317.2 b 10286.4 a 3201.4 bc 3753.8 b 10157.2 a 1771.4 c 10832.2 a 3293.2 bc 3864.3 b 10466.9 a 1888.4 c 10715.3 a 5304.0 b 5814.5 a 4972.5 b 1481.8 c 7213.4 a 4735.9 b 6318.5 a 5015.9 ab 981.2 c 6102.3 a 4857.7 b 6210.5 a 5006.6 ab 1088.5 c 6340.4 a

218.8 c 289.5 c 732.6 b 480.7 bc 3043.2 a −818.6 b 59.1 a −909.6 b −752.8 b 78.4 a −596.3 c 108.5 b −557.7 c −488.5 c 713.7 a 663.0 c 994.5 b 251.9 d 427.6 d 1246.4 a −459.0 d 931.1 b −996.6 f 74.1 c 1382.1 a −218.6 d 944.7 b −729.1 f 149.9 c 1353.0 a

*** ** ** NS *** NS NS

*** *** *** *** *** *** ***

*** *** * NS ** NS NS

*** *** *** *** *** *** ***

Significance Treatment Year Location Treatment × Location Treatment × Year Year × Location Treatment × Year × Location

Different letters within a column indicate significant differences among all treatments at p < 0.05. *p < 0.05, **p < 0.01 and ***p < 0.001. NS represents no significance. STM: straw mulching; CSS: surface soil compaction; PAM: polyacrylamide amendment application; SAM: sand mulching; CK: untreated control.

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temperature in 2013, indicating that CSS and PAM with brackish water irrigation may more effectively enhance soil temperature. The increase in the soil temperature for CSS and SAM may result from the increase in the thermal conductivity of denser soil (Kranabetter and Chapman, 1999; Li, 2003) or improvement of volume fraction of solid phase (AbuHamdeh, 2003; Lipiec and Hatano, 2003; Lipiec et al., 2007). In our study, the four controlling methods significantly reduced daily soil evaporation in bare strips during the two years. The reduction in the soil evaporation depended on the different controlling methods. The presence of straw in STM intercepted solar radiation and reduced wind speed close to the soil surface (Horton et al., 1996; Li et al., 2013), thereby gave the lowest daily soil temperature of 20-cm soil profile in 2013 and conserved water by the suppression, leading to the lowest soil evaporation among all treatments in 2013. In 2014, the lowest daily soil evaporation was recorded in SAM. One reason may be the improvement of topsoil porosity, suppressing the capillary action (Modaihsh et al., 1985). Another possible reason for this could be improvement of resistance to soil evaporation due to the presence of sand on the soil surface. The result is in agreement with the previous studies that a coarse-textured layer overlying fine-textured soil suppresses evaporation (Yamanaka et al., 2004; Diaz et al., 2005; Assouline et al., 2014). The four controlling methods also decreased the ETb−h especially in 2013, mainly due to the dramatic reduction in the soil evaporation in bare strips. High soil salinity may reduce cotton growth, although cotton is a tolerant crop to salinity (Zhang et al., 2014). The four controlling methods could greatly delay salt accumulation for 1-m soil profile in bare strips, thus moderate the salt accumulation in the whole domain. The lower ΔS for whole domain in 1-m soil profile was found in STM and PAM among all treatments. The straw in STM reduced soil evaporation to conserve more water in the soil, thus promoted ion exchange and absorption and increased the total dissolved salts, leading to a higher salt-leaching efficiency during the irrigation period (Zhao et al., 2014). As for PAM, because it may have a notable impact on improvement of soil saturated hydraulic conductivity (Zahow and Amrhein, 1992), thereby greatly facilitated more salt leaching, in agreement with the results found in the coastal saline soils by Wang et al. (2012). Due to significant differences in soil temperature, evaporation and salinity among all treatments, the four controlling methods may further affect the yield and WUE for cotton. In our study, the four controlling methods slightly increased WUE owing to the reduction in the ETtotal for the four controlling methods during the both seasons, even though some of them slightly decreased the yield. The positive impacts of the four controlling methods on yield and WUE could be explained by more water application in cotton transpiration due to the reduction in soil evaporation. Among all treatments, SAM gave the highest yield and WUE for cotton during the both seasons, indicating that the practice may be more effective than the other three controlling methods in crop productivity at this experimental site. The possible reasons may be attributed to the greater SWC, higher soil temperature and lower soil salinity which may increase the microbial biomass and enzyme activity in main root zone (Qiu et al., 2014; Ren et al., 2016) and the capacity of photosynthesis.

Table 5 Cotton yield, aboveground biomass, harvest index (HI), total evapotranspiration (ETtotal) and water-use efficiency (WUE) for the four controlling methods and CK in 2013 and 2014. Year

Treatment

2013

STM CSS PAM SAM CK STM CSS PAM SAM CK

2014

Significance Treatment Year Treatment × Year

Yield (t ha−1) 6.34 6.32 6.27 6.42 6.07 5.19 5.25 5.34 5.85 5.42 NS *** NS

a a a a a a a a a a

Biomass (t ha−1)

HI (%)

ET (mm)

13.34 a 13.97 a 13.72 a 13.74 a 13.66 a 10.30 a 9.63 a 8.51 a 10.03 a 9.20 a

47.5 45.2 45.7 46.7 44.4 50.4 54.5 62.7 58.3 58.9

580.8 582.5 581.4 587.0 617.5 572.8 548.1 561.1 570.7 573.7

NS *** NS

NS *** NS

** *** NS

b b b b a a a a a a

WUE (kg m−3) 1.09 1.08 1.08 1.09 0.98 0.91 0.96 0.95 1.02 0.94 NS *** NS

Different letters within a column indicate significant differences all treatments at p < 0.05. **p < 0.01 and ***p < 0.001. NS represents no significance. STM: straw mulching; CSS: surface soil compaction; PAM: polyacrylamide amendment application; SAM: sand mulching; CK: untreated control.

in 2013 and 2014, respectively. In 2013, the four controlling methods slightly increased HI by 1.9–7.6% compared to CK (p > 0.05). By comparison, the higher HI was only found in PAM in 2014. In addition, the cotton yield in 2013 was much higher than that in 2014 (p < 0.001), while the HI in 2013 was lower than that in 2014. The possible reason was brackish water irrigation in 2014 so that it lowered stem and leaf production, leading to little difference between cotton yield and aboveground biomass, and then giving a high HI. Due to no SWC data at sowing and no treatment at seedling stage, the ET at seedling stage was assumed as 50 mm to estimate the ET during the entire growing season (ETtotal) and the WUE for cotton based on the findings reported by Liu et al. (2006) at this experimental site. In general, lower WUE was found in 2014 which was also caused by brackish water irrigation. There were no significant differences (p > 0.05) in WUE among all treatments. Compared to CK, the four controlling methods almost increased WUE by 10.2–12.2% and 1.1–8.5% during 2013 and 2014 seasons, respectively, with the exception of STM in 2014. The highest WUE was found in SAM during the both seasons. The order of WUE was SAM > STM > CSS > PAM > CK in 2013 and SAM > CSS > PAM > CK > STM in 2014. 4. Discussion 4.1. Effect of the four controlling methods on soil properties and cotton productivity Soil temperature is an essential factor for influencing soil microbial activity, the respiration rate of fields soils and root extension. In the present study, the four controlling methods provided lower CVs of daily soil temperature of 20-cm soil profile in bare strips with respect to CK during the two years, suggesting that the four controlling methods could stabilize soil temperature. This is probably because the four controlling methods increased SWC and thermal capacity making less differences between maximum and minimum soil temperature. There were different effects on soil temperature due to different controlling methods. Average daily soil temperatures of 20-cm profile for STM and PAM in bare strips were lower than that for CK during the both seasons except for STM in 2014 when compared to CK, likely because of the reduction of heat from solar energy for STM and improvement of water retention for PAM. As for CSS and SAM, the two methods greatly increased the soil temperature in 2014 but had no effects on daily soil

4.2. Application and sustainability of the four controlling methods In the present study, the four controlling methods can regulate soil temperature, greatly reduce daily soil evaporation and salinity, thus generally enhance WUE for cotton. The findings indicate that the controlling methods provide a potential opportunity to control water loss, prevent the risk of soil degradation by salinization and increase crop productivity. However, different controlling methods had different impacts on soil temperature, implying that the methods may maximize their positive effects on crop productivity in different circumstances. High or low soil temperature may be harmful to crop growth. It has 356

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canopy development. Also, the four controlling methods decreased the ET from late seedling stage to harvest. Moreover, the four controlling methods greatly reduced salt accumulation in the bare strips 40.3–116.6% for 40-cm soil profile and 20.2–92.8% for 1-m soil profile, consequently moderating the salt accumulation in the whole domain. In addition, the four controlling methods slightly increased the WUE for cotton by 10.2–12.2% and 1.1–8.5% during 2013 and 2014 seasons, respectively, except for STM in 2014. Among all treatments, the highest yield and WUE were obtained in SAM during the two seasons. The combination of controlling method and film-mulched drip irrigation could provide a feasible option to moderate soil evaporation and salinity and enhance crop productivity in the arid region of southern Xinjiang and other similar regions in the world. It should be noted that the conclusions of our study were based on two years of investigation and the salinity of irrigation water during the two growing seasons was different. To evaluate the sustainability for the application of controlling methods in bare strips under film-mulched drip irrigation, further long-term studies should be carried out.

been reported that > 38 °C or < 10 °C is detrimental for cotton seedling emergence and root metabolic activity (Singh and Dhaliwal, 1972; Nabi and Mullins, 2008). In this study, the soil temperatures for all treatments were within the range of 10–38 °C, thus could not visibly affect cotton growth. CSS and SAM generally increased soil temperature, revealing that the both practices could be recommended at seedling stage to promote the root growth and canopy development for cotton when soil temperature is low. Furthermore, CSS and SAM could also protect cotton seedling from strong wind at initial stage. In contrast, STM and PAM decreased soil temperature, which are disadvantageous to the crop establishment at seedling stage. However, the two practices could be applied at flowering or early boll stages to relieve the heat stress for root growth and nitrate uptake for cotton (Munevar and Wollum, 1982; Huang et al., 2001; Arai-sanoh et al., 2010) when soil temperature becomes high. In our short-term experiment, the four controlling methods in the bare strips with film-mulched drip irrigation provided some benefits for controlling soil evaporation and salinity as well as improvement of cotton productivity. On the other hand, the long-term environmental risk of the controlling methods in the bare strips with film-mulched drip irrigation should also be taken into account. STM is good for sustainable material recycling but it may cause lower crop productivity due to its slow decomposition, the reduction in available nitrogen (Kar and Kumar, 2007), inhibiting root extension, and aeration problem. Thus it is important to improve the productivity in STM through suitable nutrient management (e.g. larger nitrogen inputs) (Liu et al., 2003) and optimum application rate of straw. As for CSS, soil compaction can be conducted easily by using a tractor or other traffic tools but heavy compaction could pose a risk to root extension and aeration in soil. Hilfiker et al. (1984) noted that the ranges of bulk density detrimental to crop root growth have been estimated at 1.6 g cm−3 for clay, 1.4–1.8 g cm−3 for loamy and 1.7–1.9 g cm−3 for sandy soils. Thus, the proper intensity of compaction in the bare strips with film-mulched drip irrigation should be further studied. As for PAM, it could be beneficial to control soil evaporation and salinity as well as promote crop productivity. However, the cost of polyacrylamide is higher than the other methods. Moreover, more water is needed to dissolve polyacrylamide due to the slight solubility of polyacrylamide. In SAM, the crop productivity was higher than that of the other three controlling methods but the main problem of this method is the risk of soil degradation by improvement of sand content in soil. In the Loess Plateau, Qiu et al. (2014) pointed out that gravel-sand mulching significantly increased sand content in sandy soil and had adverse effects on total N and C, microbial biomass C, and enzyme activities after its 16-year application. In our study, the soil texture was silt loam with 41.4% sand at our experimental site was much lower than that in the study (72.9%) from Qiu et al. (2014). Moreover, the controlling methods only applied in the bare strips and could decrease their adverse impacts in comparison with that applied in the whole soil domain. Thus, SAM at our experimental site could last for many years, but the potential risk of soil degradation should be still concerned. It could be improved by providing supplemental inputs of organic matter and nitrogen to improve soil structure and nutrient in soil (e.g., manure and crop residue) (Qiu et al., 2014).

Acknowledgments This study was financially supported by the National Natural Science Foundation of China (Grant Nos. 51679190 and 51409213) and the National Key Research and Development Program of China (Grant Nos. 2016YFC0501401-02 and 2016YFC0501405-04). References Abu-Hamdeh, N.H., 2003. Thermal properties of soils as affected by density and water content. Biosyst. Eng. 86 (1), 97–102. Al-Uzairy, B.N., 2015. The effectiveness of two soil amendments: gypsum and polyacrylamide on soil erosion under saline conditions in Australia. Int. J. Environ. Sci. Dev. 6 (5), 375–380. Allen, R.G., Pereira, L.S., Raes, D., Smith, M., 1998. Crop evapotranspiration-guidelines for computing crop water requirements. FAO Irrigation and Drainage Paper 56. FAO, Rome. Arai-sanoh, Y., Ishimaru, T., Ohsumi, A., Kondo, M., 2010. Effects of soil temperature on growth and root function in rice. Plant Prod. Sci. 13 (3), 235–242. Assouline, S., Narkis, K., Gherabli, R., Lefort, P., Prat, M., 2014. Analysis of the impact of surface layer properties on evaporation from porous systems using column experiments and modified definition of characteristic length. Water Resour. Res. 50 (5), 3933––3955. Chen, W., Jin, M., Liu, Y., Xian, Y., Huang, J., 2017. Monitoring cotton root growth dynamics under mulched drip irrigation using monirhizotron technique. Trans. Chin. Soc. Agric. Eng. 33 (2), 87––93. Díaz-Pérez, J.C., Phatak, S.C., Giddings, D., Bertrand, D., Mills, H.A., 2005. Root zone temperature, plant growth, and fruit yield of tomatillo as affected by plastic film mulch. HortScience 40 (5), 1312–1319. Davenport, J.R., Schiffhauer, D.E., 2000. Cultivar influences cranberry response to surface sanding. HortScience 35 (1), 53–54. Diaz, F., Jimenez, C., Tejedor, M., 2005. Influence of the thickness and grain size of tephra mulch on soil water evaporation. Agric. Water Manage. 74 (1), 47–55. Gale, W.J., McColl, R.W., Fang, X., 1993. Sandy fields traditional farming for water conservation in China. J. Soil Water Conserv. 48 (6), 474––477. Gupta, R., Acharya, C.L., 1993. Effect of mulch induced hydrothermal regime on root growth, water use efficiency, yield and quality of strawberry. J. Indian Soc. Soil Sci. 41 (1), 17––25. Gupta, J.P., Gupta, G.N., 1985. Effect of mulches on hydro-thermal environment of soil and crop production in arid western Rajasthan. Ann. Arid Zone 24 (2), 131––142. Hartmann, P., Zink, A., Fleige, H., Horn, R., 2012. Effect of compaction, tillage and climate change on soil water balance of Arable Luvisols in northwest Germany. Soil Tillage Res. 124, 211–218. Hernández, M., Echarte, L., Della Maggiora, A., Cambareri, M., Barbieri, P., Cerrudo, D., 2015. Maize water use efficiency and evapotranspiration response to N supply under contrasting soil water availability. Field Crops Res. 178, 8–15. Hilfiker, R.E., Lowery, B., Daniel, T.C., 1984. Soil Penetrometer Resistance and Bulk Density Characteristics Utilizing Four Tillage Systems. ASAE Paper No. 84–2028. ASAE, St. Joseph, MI. Horton, R., Bristow, K.L., Kluitenberg, G.J., Sauer, T.J., 1996. Crop residue effects on surface radiation and energy balance. Theor. Appl. Climatol. 2 (1–2), 27–37. Hu, X.T., Hu, C., Wang, J., Meng, X.B., Chen, F.H., 2009. Effects of soil water content on cotton root growth and distribution under mulched drip irrigation. Agric. Sci. China 8 (6), 709–716. Huang, B., Liu, X., Xu, Q., 2001. Supraoptimal soil temperatures induced oxidative stress in leaves of creeping bentgrass cultivars differing in heat tolerance. Crop Sci. 41 (2), 430–435. Huang, Y., Chen, L., Fu, B., Huang, Z., Gong, J., 2005. The wheat yields and water-use

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