Organic manure as an alternative to crop residues for no-tillage wheat–maize systems in North China Plain

Field Crops Research 149 (2013) 141–148

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Organic manure as an alternative to crop residues for no-tillage wheat–maize systems in North China Plain Xiaoqin Dai a , Yunsheng Li a,∗ , Zhu Ouyang a , Huimin Wang a , G.V. Wilson b a Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China b USDA-ARS National Sedimentation Laboratory, Oxford, MS 38655, USA

a r t i c l e

i n f o

Article history: Received 15 October 2012 Received in revised form 28 April 2013 Accepted 28 April 2013 Keywords: NT Soil properties Grain yield Biomass Weeds

a b s t r a c t No-tillage (NT) can provide both environmental and economic benefits and has been recognized as a sustainable land use practice in many areas worldwide. NT has induced some concerns in the North China Plain (NCP), e.g. unstable crop yield and fodder shortage, with regards to the amount of crop residues retained on the soil surface. The objective of this study was to explore whether or not manure inputs are a viable alternative to crop residue in no-till wheat and maize rotation systems in NCP. Field experiments were initiated in October 2004 including three management operations: conventional tillage with residue removed (CTr), NT with crop residue left on soil surface (NTc), and NT with manure inputs (NTm); and two fertilizer application practices: splitting fertilizer inputs (SF) and concentrated fertilizer inputs (CF). These treatments were arranged in a randomized complete block design, with three replications, and continued over a 4-year period. Crop yield, soil properties and weed population were measured in a wheat–maize double crop system. Compared to CTr, NT had a trend of reducing wheat biomass and grain yield which reduced by 4% and 6%, respectively, for NTc, and 5% and 4%, respectively, for NTm. Tillage treatments, thus use of manure instead of residue, had no significant effects on maize biomass and yield. Fertilizer application practices had no significant effects on biomass and yield of both crops. Continuous NT for 4 years significantly increased the bulk density, soil water content, soil organic carbon (SOC) of the surface soil, but decreased the soil electrical conductivity (EC). The increase in SOC in NTm was higher than in NTc. Although soil EC decreased less in NTm than in NTc, the effects of soil EC could be neglected in the study. The NTc or NTm significantly inhibited the dominant weed in wheat field. The CF inhibited the flixweed (Descurainia sophia) growth compared to the SF. The manure inputs were found to be a viable alternative to crop residue in this NT wheat–maize system in the NCP. © 2013 Elsevier B.V. All rights reserved.

1. Introduction The North China Plain (NCP) is the largest and most important agricultural region of China in that it represents 20% of total Chinese food production. Winter wheat–summer maize double cropping is widespread along with intensive soil tillage. In this system, wheat is seeded in October and harvested the following June, after which maize is immediately seeded and harvested in mid-September. The conventional management practice includes intensive soil cultivation, low organic manure inputs, and essentially complete crop residue removal. This present system has posed severe environmental problems. Ideally, good crop yields with minimal impact on soil quality and ecological factors are needed for sustainable agriculture in this region.

∗ Corresponding author. Tel.: +86 10 64889029; fax: +86 10 64851844. E-mail addresses: [email protected] (X. Dai), [email protected] (Y. Li). 0378-4290/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.fcr.2013.04.027

No-tillage (NT) with crop residue left on the soil surface has recently become more popular in many areas of the world due to its benefits, e.g. protects soil and water from losses, improves crop productivity and soil fertility, reduces costs of field preparation, fuel, equipment and labor compared to conventional tillage (CT) practices (Wang et al., 2006). Following the recognition of the increased rate of degradation of the environment, the Chinese government actively stimulated demonstration and extension of conservation tillage practices since 2002, including NT technology. Numerous studies on NT technology have been conducted in different ecological regions of China with a variety of local climate and soil conditions (He et al., 2009; Qin et al., 2010). These studies found that NT could increase grain yield, improve soil properties, and increase soil organic carbon and total nitrogen contents in the upper soil layers (Du et al., 2010; Hou et al., 2012), reduce soil temperature, reduce impact of raindrops on soil, and to reduce erosion (Dormaar and Carefoot, 1996). The tillage operations also had a significant influence on soil EC (Hasinur et al., 2008). In NCP, large salinated areas are distributed in the middle

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and east where soil evaporation increased soil salt concentration. The NT with soil cover by mulch was promising for inhibiting soil salt accumulation. However, in wheat–maize rotation system of NCP, excessive maize residue left on the soil surface after harvest can impede penetration of a NT planter. Lack of penetration can decrease the wheat sowing quality which influences wheat emergence and yield, thereby inhibiting the adaption of NT in this region (Li et al., 2006). The NCP is also an important region for livestock production. In 2009, the NCP’s annual production of meat, eggs and milk were respectively 18.8, 12.3 and 12.2 Mt, and respectively supplied 25%, 45% and 33% of total those production in the country (http://www.stats.gov.cn). Not only was a mass of fodder required, but it is inevitable to produce abundant animal waste. Only in Shandong, Henan and Hebei, the production of livestock manure almost amounted to 500 Mt in 2010, which was 23% of the total of the nation (Geng et al., 2013). It provided a lot of nitrogen and phosphorus nutrients for crop growth. For example, the nitrogen content in harvested maize stover was 1.15% and the average N use efficiency is 15% for cattle (IAEA, 2008), which means that about 85% N in maize stover excreted into manure. If the N loss was assumed to re-deposition, about 0.98 kg N in maize stover was recycled to the field when 100 kg maize stover is fed to cattle. So, the application of chemical fertilizer was greatly reduced when proper manure was added to the field. Manure amendments also can improve soil physical properties, nutrient status, and increase soil organic C (SOC) levels. Thus manure amendments may be a suitable practice for food security and agricultural sustainability. However, the NT leaving a large amount of maize residue on the field can result in shortage of fodder. We can take cattle as an example. For long term health, adult cattle should consume at least 2% of their body weight as forage (dry matter basis) and produce 6% of their body weight manure per day. Assuming one adult cattle is about 420 kg, and then one cattle need consume 8.4 kg maize stover and produce 25 kg manure daily (Powell et al., 2013). If all maize stover (9 Mg ha−1 ) in one hectare maize field was used to feed cattle, three cattle could be fed for about one year and produce 27 Mg manure which can meet the one hectare maize field requirement according to the limiting manure application to cropland to a maximum of 30 Mg ha−1 (Wang et al., 2010). Therefore, food security and livestock development must consider whether or not NT with manure substituted for residue retention is a suitable alternative for sustainable agriculture in this region. Agbede and Ojeniyi (2009) found that no tillage, with or without mulch, in combination with manure gave the best tillage–manure system for sorghum. This combination improved soil fertility and yield of sorghum more than other tillage–manure combinations. The application of manure to no-till can assist in reducing the deleterious effects of mechanical impedance (Mosaddeghi et al., 2009). However, there is little information concerning the combined impacts of tillage systems and manure application in NCP for wheat–maize system. Weeds are an important component in farmlands in that they compete for light, nutrient, water and other resources with crops, thereby influencing crop growth and yield. A switch from conventional to conservation tillage systems alters the weed species composition, total amount and temporal pattern of emergence of weeds, and thus results in a modified weed–crop relationship (Tuesca et al., 2001). Many studies found that NT had lower weed densities than CT treatments (Campbell et al., 1998). However, Swanton et al. (1999) did not observe consistent relationships between weed density and tillage system but found differences in composition of weed populations between CT and NT systems. Weed community changes fluctuated and were dependent on environment, location, and timing of management practices. There is a lack of information on how NT and residue management systems affect weed growth in NCP.

Fig. 1. Monthly rainfall and total rainfall during wheat (Tw), maize (Tm) and two cropping seasons (Twm) growth periods at Yucheng, Shandong Province of China.

Thus, the main objective of the study was to compare the effects of CT with residue removal, and NT with residue left on soil surface or with dairy manure inputs on crop yield, soil properties and weed growth in NCP in order to elucidate whether manure inputs are a viable alternative to crop residue for NT systems in NCP. 2. Materials and methods 2.1. Experimental site A field experiment was initiated in 2004 at the Yucheng Comprehensive Agricultural Experimental Station (YCES; 36◦ 57 N, 116◦ 36 E, 28 m a.m.s.l.), which belongs to Chinese Ecosystem Research Network (CERN). It is located in the southwest of Yucheng County, Shandong Province. Landform of this area is Yellow River alluvial plain, and representative of typical conditions of Huang-Huai-Hai Plain. The climate is a temperate, semi-humid monsoon climate. Average annual temperature is 13.1 ◦ C, and is highest in July when daily averages range from 25 to 27 ◦ C and lowest in January with a range of −0.8 to −4.1 ◦ C. In the growing season, rainfall data were collected from rainfall meters adjacent to the experimental field (Fig. 1). Annual mean precipitation is 581 mm, with about 70% of total precipitation in June–August. Soils at YCES are alluvial deposits of Yellow River and classified as fluvo-aquic loam. The texture is predominately silt loam (15% sand, 60% silt, and 25% clay) with a bulk density of 1.31 Mg m−3 . The dominant cropping system is winter wheat (Triticum aestivum) and maize (Zea mays) double cropped. 2.2. Treatment and crop management The experiment was set up as a factorial design including three tillage levels (NT with crop residue left on soil surface, NTc; NT with dairy manure substituted for residue removed, NTm; and CT with residue removal, CTr), and two fertilizer levels (splitting fertilizer inputs, SF and concentrated fertilizer inputs, CF). Each treatment had three replications and was arranged in randomized complete block. The plot area was 40 m × 7.5 m (300 m2 ). NT plots were seeded directly with a no-till planter with previous crop residue (cut to 5 cm) returned on the soil surface (NTc) or without previous crop residue but with fresh dairy manure inputs (NTm) which had the same nitrogen amounts as crop residue returned in NTc. In NT plots, the soil surface was not disturbed except by planting. Maize mulch piled up in the process of seeding timely was cleaned

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up by hand. The CTr treatments were ploughed by rotary tillage to 180–200 mm depth without previous crop residue left on the soil surface or dairy manure inputs. For split fertilizer inputs (SF), fertilizers were applied at sowing (40% of the total N as a basal dressing), turning-green (36%, the first leaf growing in the early of spring grew to 1–2 cm from soil surface and the phenomena were seen on a half of wheat seedling in the field) and flowering stage (24%) of wheat and elongation stage of maize. For concentrated fertilizer inputs (CF), the fertilizer was applied at sowing of wheat and elongation stage of maize. In all of the plots, 285 kg N ha−1 were applied for wheat and 207 kg N ha−1 were applied for maize, in which the N amounts of crop residue returned in the NTc plots and dairy manure inputted in the NTm plots was accounted for as if applied with the basal fertilizer. The dairy manure was collected from a near cattle farm. The N, P and K content of the manure was 19.6, 10.5 and 16.7 g kg−1 , respectively. The P and K was applied with N in the compound fertilizer which is an inorganic chemical fertilizer and contains N (as urea), P (as P2 O5 ) and K (as K2 O) at rate of 12:19:13, and the application rates were 116 kg N ha−1 , 178 kg P ha−1 and 122 kg K ha−1 , respectively (Hou et al., 2012). Wheat was seeded in mid-October of each year, in rows spaced 20 cm apart at a seeding rate of 188 kg ha−1 . The crop was harvested in early-June of the following year. All treatments received similar irrigation schemes, namely, surface irrigations of 75 mm were applied, respectively, on turning-green and flowering stage of wheat after broadcasting of fertilizers. Maize was planted with a population of 64,000 ha −1 in late-June of each year and was harvested in mid-September. For maize growing season, NT conducted for all plots and all other cultural practices were the same.

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corresponding to the aboveground biomasses were determined. Analyses were conducted on weed density, aboveground biomass per hectare and dry weight per plant. 2.5. Statistical analysis All statistical analysis was performed with SPSS software package release 16.0. Weed density data were not normally distributed. Before statistical analyses were done, a square-root transformation for weed density, biomass and dry weight per plant was used to stabilize variances. Weed density, biomass, and height along with wheat and maize biomass and grain yield were analyzed using GLM to test the effect of tillage operations and fertilizer application practices and possible interactions. The statistical significance of tillage, fertilization, soil depth and their interactions on soil physical and chemical variables were also analyzed using the GLM program. In GLM analysis, the CTr, NTc and NTm were considered as three independent tillage treatments. Means were compared using a Fisher’s protected least significant difference (LSD) test at P = 0.05. 3. Results 3.1. Crop biomass and yield

At wheat and maize harvest, aboveground biomass and grain yield was determined from three randomly sampled 3 m2 areas for wheat and 4 m2 areas for maize in each plot. Aboveground biomass was oven-dried to a constant weight and grain yield was air-dried and corrected to 12% moisture content. Soil samples were collected according to a systematic sampling design across the S-shaped transects in October 2008 when maize was harvested. Ten soil samples were collected from every plot at three depths (0–5, 5–10, 10–20 cm), composited and mixed to form a single sample per plot for each depth. The mulch layer was removed before taking the samples. Each soil sample was placed in a plastic bag at sampling and transferred to the laboratory. All visible root and fresh litter material were removed from the samples prior to sieving. A proportion of each sample was passed through a 2-mm sieve and stored at 4 ◦ C and the rest was stored after air-drying. Soil water content was determined using gravimetric methods and the bulk density was determined after drying to 105 ◦ C knowing the volume of the cores. The pH of soils was determined in a 1:2.5 soil to water suspension by a digital pH meter and electrical conductivity (EC) of soil (1:5) was measured by digital conductivity meter. The soil pH and EC were measured from field-moist soil. Soil particle size analysis was performed with a MasterSizer 2000 laser particle size analyzer produced by Malvern. Organic carbon was determined using the Walkley–Black method. Total nitrogen was measured using the Kjeldahl method.

Wheat aboveground biomass and yield ranged from 10.6 Mg ha−1 to 15.8 Mg ha−1 and 4.8 Mg ha−1 to 6.8 Mg ha−1 , respectively (Table 1). Yield and biomass were significantly different among years probably due to the differences in rainfall during the wheat growing period (Figs. 1 and 2). Tillage operation significantly influenced wheat biomass and grain yield (P < 0.05, Table 1). Wheat yields were significantly higher under CTr than NTm in 2006/2007 for CF, and wheat biomass was significantly higher in CTr than NTm in 2005/2006 for both SF and CF. In addition biomass was higher in CTr than NTc in both 2005/2006 and 2006/2007. The interaction of tillage, fertilization and year significantly influenced wheat grain yield (Table 1). Compared to CTr, the multi-year average grain yield across fertilizer treatments decreased significantly (P < 0.01) by 5% and 4% in NTc and NTm, respectively. The decrease in yield was mainly attributed to the effects in the later two years. The reduction in grain yield in the third and fourth year respectively was 9% and 7% in NTc, and 9% and 2% in NTm. The grain yield in NTm was higher than that in NTc for three of the four years for both fertilizer treatments. Fertilization had no significant effect on wheat biomass and yield, but the interaction of fertilization and year significantly influenced wheat yield (Table 1). Maize biomass and yield ranged from 14.1 Mg ha−1 to 20.1 Mg ha−1 and 5.8 Mg ha−1 to 8.6 Mg ha−1 , respectively (Table 2). Tillage treatments, fertilizer practices and their interactions had no significant influences on maize biomass and yield (Table 2). However, the year had a significant effect on maize biomass and yield (P < 0.01 for biomass and P < 0.001 for yield, Table 2) mainly due to the different rainfall amount during the maize growth period (Fig. 2). No differences were observed in yield or biomass produced among treatments for any year or fertilizer treatment. Thus, manure is a viable alternative to residue for maize production as well.

2.4. Weed measurements

3.2. Soil physical and chemical properties

Weed survey was carried out after fertilizers were applied in the green-turning stage of wheat in March 2008 and the elongation stage of wheat in mid-April 2009. The number of individuals of each dominant weed species was counted and sampled in each plot. Plant material was oven-dried at 65 ◦ C for 48 h, and dry weights

3.2.1. Bulk density, water content, pH and EC Soil bulk density in NTc and NTm plots averaged 1.45 g cm−3 and 1.41 g cm−3 in 0–5 cm, and 1.51 g cm−3 and 1.46 g cm−3 in 5–10 cm, respectively. This is an increase of 7% and 3% in 0–5 cm and 9% and 5% in 5–10 cm, respectively, compared to CTr. The NTc

2.3. Crop and soil measurements

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Table 1 Wheat aboveground biomass and grain yield influenced by tillage and fertilization methods at Yucheng, Shandong Province of China (mean ± standard error). Treatment

Aboveground biomass (Mg ha−1 )

Grain yield (Mg ha−1 )

SF

CF

SF

CF

2004/2005 CTr NTc NTm

14.8 ± 0.96 a 15.8 ± 0.17 a 13.9 ± 0.87 a

14.1 ± 0.78 a 14.4 ± 0.62 a 15.2 ± 0.50 a

5.8 ± 0.33 a 5.9 ± 0.09 a 5.6 ± 0.18 a

5.5 ± 0.26 a 5.6 ± 0.13 a 5.8 ± 0.08 a

2005/2006 CTr NTc NTm

11.9 ± 0.42 a 11.2 ± 0.29 ab 10.6 ± 0.32 b

12.1 ± 0.23 a 10.6 ± 0.38 b 10.9 ± 0.03 b

4.9 ± 0.20 a 4.8 ± 0.08 a 5.0 ± 0.17 a

5.4 ± 0.18 a 4.9 ± 0.15 a 4.9 ± 0.06 a

2006/2007 CTr NTc NTm

14.6 ± 0.78 a 13.9 ± 1.18 a 14.4 ± 0.96 a

14.5 ± 0.47 a 12.8 ± 0.38 b 13.0 ± 0.81 ab

6.4 ± 0.37 a 5.9 ± 0.27 a 6.6 ± 0.27 a

6.5 ± 0.19 a 5.8 ± 0.25 ab 5.2 ± 0.39 b

2007/2008 CTr NTc NTm

15.1 ± 0.40 a 13.9 ± 1.11 a 13.5 ± 0.53 a

14.7 ± 0.68 a 14.2 ± 0.45 a 14.8 ± 0.93 a

6.7 ± 0.09 a 6.0 ± 0.24 b 6.2 ± 0.17 ab

6.6 ± 0.18 a 6.4 ± 0.23 a 6.8 ± 0.34 a

Analysis of variance Tillage (T) Fertilization (F) Year (Y) T×F T×Y F×Y T×F×Y

*

*

ns

ns

***

***

ns ns ns ns

ns ns ** **

ns indicates not significant. Different letters on means indicates significant difference at P < 0.05 between tillage treatments within fertilizer treatments by year. * Significant at the 0.05 probability level. ** Significant at the 0.01 probability level. *** Significant at the 0.001 probability level.

Table 2 Maize aboveground biomass and grain yield influenced by tillage and fertilization methods at Yucheng, Shandong Province of China (mean ± standard error). Treatment

Aboveground biomass (Mg ha−1 )

Grain yield (Mg ha−1 )

SF

CF

SF

CF

2005 CTr NTc NTm

16.9 ± 0.61 a 18.3 ± 0.62 a 18.0 ± 0.44 a

18.0 ± 1.68 a 18.0 ± 0.87 a 20.1 ± 1.39 a

8.3 ± 0.35 a 8.6 ± 0.36 a 8.4 ± 0.35 a

8.3 ± 0.60 a 8.4 ± 0.70 a 8.6 ± 0.16 a

2006 CTr NTc NTm

15.9 ± 0.73 a 15.9 ± 0.48 a 16.2 ± 0.50 a

16.3 ± 0.50 a 15.6 ± 1.15 a 15.3 ± 0.09 a

6.7 ± 0.38 a 6.6 ± 0.24 a 7.0 ± 0.34 a

6.5 ± 0.25 a 6.2 ± 0.54 a 6.6 ± 0.33 a

2007 CTr NTc NTm

15.8 ± 0.19 a 15.9 ± 0.87 a 16.5 ± 2.15 a

15.2 ± 0.70 a 14.1 ± 0.72 a 14.1 ± 0.32 a

6.4 ± 0.18 a 6.0 ± 0.19 a 5.8 ± 0.51 a

6.3 ± 0.56 a 5.8 ± 0.25 a 5.9 ± 0.31 a

2008 CTr NTc NTm

17.8 ± 1.38 a 15.5 ± 1.71 a 16.9 ± 0.50 a

17.1 ± 1.94 a 19.3 ± 0.85 a 15.9 ± 0.21 a

8.0 ± 0.26 a 8.6 ± 0.32 a 7.8 ± 0.46 a

7.7 ± 0.29 a 8.6 ± 0.40 a 7.8 ± 0.57 a

Analysis of variance Tillage (T) Fertilization (F) Year (Y) T×F T×Y F×Y T×F×Y

ns ns

ns ns

**

***

ns ns ns ns

ns ns ns ns

ns indicates not significant. Different letters on means indicates significant difference at P < 0.05 between tillage treatments within fertilizer treatments by year. ** Significant at the 0.01 probability level. *** Significant at the 0.001 probability level.

Water content (%)

pH (soil:water 1:2.5)

EC (mS cm−1 )

SF

SF

SF

CF

0.21 ± 0.02 a 0.15 ± 0.01 b 0.22 ± 0.03 a

0.20 ± 0.04 a 9.9 ± 0.58 b 10.5 ± 0.41 b 0.94 ± 0.02 b 0.98 ± 0.03 b 10.6 ± 0.42 a 10.8 ± 0.19 a 0.16 ± 0.01 a 12.9 ± 0.37 a 11.8 ± 0.72 ab 1.15 ± 0.01 a 1.01 ± 0.03 a 11.2 ± 0.17 a 11.6 ± 0.40 a 0.22 ± 0.02 a 12.6 ± 0.19 a 12.9 ± 0.60 a 1.13 ± 0.05 a 1.16 ± 0.04 a 11.2 ± 0.38 a 11.2 ± 0.74 a

Soil depth (cm)

Treatment Bulk density (Mg cm−3 )

0–5

CTr NTc NTm

1.33 ± 0.01 c 1.48 ± 0.01 a 1.42 ± 0.02 b

1.39 ± 0.05 a 1.42 ± 0.03 a 1.39 ± 0.05 a

5–10

CTr NTc NTm

1.38 ± 0.03 b 1.51 ± 0.01 a 1.46 ± 0.03 ab

1.39 ± 0.04 b 19.2 ± 0.19 a 1.51 ± 0.02 a 19.7 ± 0.18 a 1.45 ± 0.02 ab 19.6 ± 0.36 a

10–20

CTr NTc NTm

– – –

SF

Analysis of variance Tillage (T) Fertilization (F) Depths (D) T×F T×D F×D T×F×D

CF

– – –

CF

CF

18.6 ± 0.12 b 18.6 ± 0.74 a 8.33 ± 0.01 b 8.30 ± 0.03 b 20.5 ± 0.38 a 19.9 ± 0.20 a 8.44 ± 0.03 a 8.51 ± 0.05 a 19.6 ± 0.36 ab 19.8 ± 0.53 a 8.44 ± 0.04 a 8.44 ± 0.02 a

20.1 ± 0.24 a 19.8 ± 0.21 a 20.1 ± 0.26 a

19.4 ± 0.58 a 8.44 ± 0.01 b 8.45 ± 0.01 b 0.25 ± 0.02 a 19.3 ± 0.36 a 8.59 ± 0.01 a 8.62 ± 0.07 a 0.18 ± 0.01 b 19.1 ± 0.26 a 8.56 ± 0.03 a 8.55 ± 0.00 ab 0.27 ± 0.02 a 19.8 ± 0.51 a 8.58 ± 0.02 a 8.62 ± 0.02 a 20.1 ± 0.13 a 8.64 ± 0.03 a 8.70 ± 0.04 a 19.9 ± 0.15 a 8.62 ± 0.03 a 8.67 ± 0.02 a

Organic C (g kg−1 )

Total N (g kg−1 )

C/N ratio

SF

SF

SF

CF

CF

0.25 ± 0.04 a 8.6 ± 0.22 a 0.21 ± 0.01 a 9.2 ± 0.14 a 0.26 ± 0.02 a 9.6 ± 1.21 a

10.0 ± 1.16 a 10.2 ± 1.07 a 10.0 ± 0.88 a

0.83 ± 0.03 a 0.89 ± 0.06 a 10.5 ± 0.54 a 11.1 ± 0.68 a 0.82 ± 0.03 a 0.87 ± 0.08 a 11.2 ± 0.36 a 11.1 ± 0.03 a 0.82 ± 0.03 a 0.83 ± 0.07 a 11.7 ± 1.01 a 12.1 ± 0.61 a

0.32 ± 0.02 ab 0.31 ± 0.03 a 7.5 ± 0.20 a 0.24 ± 0.02 b 0.26 ± 0.02 a 7.3 ± 0.85 a 0.33 ± 0.03 a 0.32 ± 0.01 a 8.0 ± 0.42 a

8.8 ± 0.32 a 8.0 ± 0.74 a 7.5 ± 0.20 a

0.68 ± 0.03 a 0.72 ± 0.06 a 11.0 ± 0.60 a 12.4 ± 1.58 a 0.66 ± 0.05 a 0.71 ± 0.08 a 12.2 ± 1.48 a 11.3 ± 0.27 a 0.69 ± 0.04 a 0.68 ± 0.05 a 11.7 ± 0.02 a 11.2 ± 0.59 a

***

*

***

***

ns

ns

ns

ns

ns ns

ns ns

ns ns

*

*

***

***

***

***

ns ns ns ns

ns

ns ns ns ns

ns ns ns ns

ns

ns

*

*

ns ns

ns ns

ns ns ns ns ns

*

ns ns

CF

145

ns indicates not significant. Different letters on means indicates significant difference at P < 0.05 between tillage treatments within fertilizer treatments by year. * Significant at the 0.05 probability level. *** Significant at the 0.001 probability level.

X. Dai et al. / Field Crops Research 149 (2013) 141–148

Fig. 2. Relationship of wheat and maize grain yield with rainfall amount in their respective growth periods at Yucheng, Shandong Province of China.

significantly increased bulk density of the surface soil (0–5 cm) compared to CTr for the SF treatment but the increase for CF was not significant (Table 3). However, both fertilizer treatments had significantly higher bulk density in NTc than CTr in the 5–10 cm depth. The NTm bulk density was also significantly higher than CTr in 0–5 cm depth for SF treatment but not different for CF or the 5–10 cm depth (Table 3). Tillage operations also significantly influenced gravimetric soil water content, pH and EC (Table 3). NTc increased soil water content only in the 0–5 cm for SF but not the CF or the 5–10 cm depth. NTc and NTm significantly increased the pH of 0–10 cm soil depth compared to CT (Table 3). Soil EC in NTc treatment decreased by 24% in 0–5 cm, 22% in 5–10 cm, and 21% in 10–20 cm compared to CTr (Table 3) but differences were only significant for the SF treatments. The NTm treatment had no significant effects on soil EC compared with CTr at any depth. Overall, bulk density, water content, pH and EC significantly increased as soil depth increased, but fertilization had no significant effects on soil bulk density, water content, pH and EC (Table 3).

3.2.2. Soil organic carbon and total nitrogen Soil organic carbon ranged from 7.3 g kg−1 to 12.9 g kg−1 with a consistent decrease with depth in all plots. Soil organic carbon in the 0–5 cm was significantly higher in NTc and NTm compared to CTr for SF and for CF in NTm. Differences in NTc and NTm were not significant for any depth or fertilization treatment. Thus, manure is a viable alternative to residue from a C sequestration standpoint.

Table 3 Soil profile distribution of soil physical and chemical properties as affected by tillage and fertilization methods in October 2008 at Yucheng, Shandong Province of China (mean ± standard error).

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Total soil nitrogen showed a similar trend as SOC with a decrease with depth and NTc and NTm treatments being significantly greater than CTr at the soil surface (Table 3). For 0–5 cm, total soil nitrogen in NTc and NTm increased by 13% and 20%, respectively, compared to CTr. The ratio of C/N increased by 5% in NTc and NTm compared to CTr but differences in C/N due to tillage operations were not significant. 3.3. Weed density and biomass 3.3.1. Flixweed density and biomass During the experiment, 10 weeds species were identified in early growth stage of wheat. Flixweed (Descurainia sophia) was the dominant weed species and other weed species were sporadic in the field. Weed species and biomass were collected over the whole plot in 2008 which influenced the occurrence of weeds in spring of 2009. Although the flixweed was still the dominant weed species in 2009, its density was decreased greatly. The flixweed density was 3.7–16.0 plant m−2 in 2008 and 0.6–2.3 plant m−2 in 2009, and among all tillage operations it was the highest in CTr and the lowest in NTm for both years (Table 4). Compared to CTr, flixweed density decreased by 10–34% in NTc, and 45–61% in NTm but was not statistically significant. The reduction was greater in NTm than in NTc particularly for the SF treatment as fertilization influenced flixweed density in wheat. Flixweed density in CF decreased by 47–58% compared to SF. However, tillage, fertilization and their interaction had no significant influence on flixweed density for both years (Table 4). The biomass of flixweed in CTr system also was the highest among all the treatments averaging 81.8 kg ha−1 in 2008 and 74.8 kg ha−1 in 2009 (Table 4). Flixweed biomass was 1.6–4.0 times as much as in CTr than in NTc and 2.9–5.2 times that in NTm. Moreover, in 2008, flixweed biomass averaged 58.3 kg ha−1 in SF compared to 20.5 kg ha−1 in CF across tillage treatments, and in 2009, 69.5 kg ha−1 in SF and 28.2 kg ha−1 in CF. Flixweed biomass in SF treatment was about 3 times that of CF for both years. Thus, flixweed biomass was significantly affected by tillage operations and fertilization in 2008, and significantly influenced by fertilization in 2009 (Table 4). The dry weight per plant of flixweed was 0.2–0.8 g in 2008, and 2.9–5.3 g in 2009 (Table 4). It was lower in 2008 than in 2009 because the field survey in 2008 was conducted at green-turning stage of wheat, and in 2009 at elongation stage. Both years, the dry weight per plant of flixweed was the highest in CTr and lowest in NTc. Tillage operations significantly influenced the dry weight per plant of flixweed in 2008 but not in 2009 (Table 4). Flixweed dry weight per plant in CTr system was 0.8–2.3 times that of NTc and NTm treatments. Fertilization influenced the dry weight of flixweed, but the difference was not significant (Table 4). 3.3.2. Flixweed height In 2009, flixweed height was measured. Flixweed height averaged 41.4–51.7 cm (Table 4). Tillage operations significantly influenced flixweed height but fertilization had no significant effect (Table 4). Compared to CTr, flixweed height decreased by 25% in NTc and 19% in NTm, which indicated NT inhibited weed growth. 4. Discussion 4.1. Effects of tillage and fertilization on grain yield The study found that NT had a trend of decreasing wheat yield especially in the last two years. The reduction in grain yield in the third and fourth year was similar to the results of Jia et al. (2004) in North China Plain, who found continuous NT in the first 3 years had no influence on wheat yield, but afterwards NT significantly

decreased wheat yield. Many studies found that wheat grain yield in NT was higher than in CT, but the effects were significant only in non-irrigated dry years, whereas in wet years, the trend was reversed (Peng and Zhang, 2006). In this study, plots were irrigated when under water stress. Irrigation combined with the clear relationship between rainfall and yield led to the soil water content in NTc and NTm being significantly higher than in CTr. Thus, soil moisture status had no significant negative effects on the difference of grain yield among the treatments. For NTc plots, crop residue impeded the efficiency of the NT planter. Li et al. (2006) have found that excessive residue shallowly mixed into soil where seed was placed results in a less consolidated seedbed and reduced wheat emergence and yield. Moreover, a large amount of residue left on the soil surface provides sufficient carbon source for soil microbial activities which can immobilize available nitrogen during residue decomposition (Bremer and Kuikman, 1997). Soil nutrient limitation was another possible reason of wheat yield reduction in the NTc plots. In the NTm plots, wheat yield also declined compared to CTr, but the reduction was less than in NTc plots. Wheat emergence in CTr was superior to that in NTm because CT can produce a more favorable seedbed compared to NTm even with the lower crop residue cover on the surface than in the NTm. For the NTc and NTm plots, soil bulk density and pH increases were other possible reasons for wheat yield reduction (Li et al., 2006). Tillage operation had no significant effects on maize biomass and yield, because the tillage and other management practices were the same in all treatments in maize growth period. Furthermore, due to no impedance from wheat residue, NT maize planter effectively penetrated the untilled soil and placed seed at the optimum depth for plant emergence. Maybe the differences in crop biomass and yields would be found between tillage operations because the long-term conventional tillage damaged to soil structure and developed a compaction pan at 15–20 cm depth, inversely, the long-term no tillage improved soil properties which were advantageous to crop growth (Chen et al., 2008). Considering the economic benefits and input costs of the different tillage systems, including the cost of seed, chemical fertilizer, pesticide, labor and the transport and processing – of residues to the animal, chopping of maize stalks into short segments, and the transport of animal manure to the field, etc., the input costs of NTc and NTm respectively decreased 10% and 8% and the economic benefits in no-tillage system increased by 17–19% compared to conventional tillage. No significant difference in benefits and costs between NTc and NTm was found (unpublished results). Thus, manure is clearly a viable alternative to residue in no-tillage system from an economic effects standpoint. 4.2. Effects of tillage on soil properties Bulk density is an important physical parameter of soil, which is closely related to other physical and chemical properties, that influences soil fertility and crop growth. Generally a negative relation was found between bulk density and grain yield (Gill and Aulakh, 1990). In this study, soil bulk density had an increasing trend after four years of continuous NT in wheat and maize rotation. For the NTc and NTm plots, soil bulk density increases were other possible reasons for wheat yield reduction. Hasinur et al. (2008) also found that NT increased bulk density compared to CT. However, there existed different opinions on the effects of tillage on bulk density. Dao (1996) reported that NT soil had lower bulk density than that under CT soil. López-Fando and Pardo (2009) observed no significant effect of tillage methods on soil bulk density. These contradictory results may be due to differences in crop species, soil properties, climatic characteristics and their complex interactions. In this region, further study was needed to determine whether long-term NT will significantly increase bulk density.

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147

Table 4 Flixweed density, dry weight per plant, biomass, and height and their analysis of variance influenced by tillage and fertilization methods in wheat field at Yucheng, Shandong Province of China (mean ± standard error). Year

2008

Treatment

CTr NTc NTm

Analysis of variance Tillage (T) Fertilization (F) T×F 2009

CTr NTc NTm

Analysis of variance Tillage (T) Fertilization (F) T×F

Density (plants m−2 )

Dry weight (g plant−1 )

Aboveground biomass (kg ha−1 )

Height (cm)

SF

CF

SF

CF

SF

CF

SF

16.0 ± 6.7 a 10.0 ± 5.0 a 4.6 ± 1.3 a

5.2 ± 1.5 a 3.9 ± 1.6 a 3.7 ± 1.3 a

0.80 ± 0.0 a 0.31 ± 0.0 c 0.44 ± 0.0 b

0.78 ± 0.1 a 0.24 ± 0.0 b 0.33 ± 0.0 b

124.2 ± 48.8 a 30.4 ± 15.0 b 20.3 ± 5.9 b

39.4 ± 9.9 a 10.8 ± 5.2 b 11.3 ± 3.0 b

– – –

ns ns ns 2.3 ± 0.8 a 1.5 ± 0.6 a 0.8 ± 0.2 a ns ns ns

0.6 ± 0.1 a 1.1 ± 0.5 a 0.7 ± 0.2 a

***

**

*

*

ns

ns

5.3 ± 0.2 a 3.6 ± 0.1 b 3.7 ± 0.8 ab ns ns ns

4.0 ± 0.7 a 2.9 ± 0.4 a 3.1 ± 0.8 a

123.6 ± 44.6 a 54.8 ± 23.5 a 30.1 ± 7.0 a

CF – – –

– – – 26.0 ± 8.9 a 37.2 ± 20.7a 21.4 ± 7.1 a

51.4 ± 2.5 a 37.9 ± 2.1 b 42.3 ± 1.0 b

ns

***

*

ns ns

ns

51.7 ± 2.6 a 39.2 ± 3.9 b 41.4 ± 1.6 b

ns indicates not significant. Different letters on means indicates significant difference at P < 0.05 between tillage treatments within fertilizer treatments by year. * Significant at the 0.05 probability level. ** Significant at the 0.01 probability level. *** Significant at the 0.001 probability level.

This study indicated that tillage operations and soil depth significantly influenced soil EC. The NTc significantly inhibited the accumulation of salt in the soil surface. In the middle and east of the North China Plain, a large area of saline water is distributed in the shallow ground-water aquifer. In the area, the increase of soil salt concentration mainly comes from strong evaporation effect. A large amount of residue cover decreased soil evaporation, so it reduced the accumulation of soil salinity in the topsoil (Zhang et al., 2009). The result was different from that of Hasinur et al. (2008), who found that NT had the highest EC compared to other tillage operations. Because NT in their study was set up in continuous apple orchard and CT in wheat–soybean rotation, in which crop type was different, the results were not attributed to tillage effect alone. Compared to CTr, the NTm had no significant effect on soil EC. The previous study indicated that the effect of soil salinity could be neglected when soil EC was lower than 0.2 mS cm−1 . Many crops yields are inhibited when soil EC is higher than 0.4–0.8 mS cm−1 (US Salinity Laboratory Staff, 1954). The NTc seems to be promising for these saline and alkali soils. However, in our study, soil EC ranged from 0.15 to 0.33 mS cm−1 and about 0.2 mS cm−1 in the topsoil. Therefore, soil salinity had no significant influence on crop growth in the study, but the long-term effects of different tillage operations on soil EC need further study. Compared to CT, soil organic carbon and total nitrogen were accumulated at surface several centimeters in NT with a strong concentration gradient from the surface to subsurface (Limousin and Tessier, 2007). In our study, NT also increased soil organic carbon and total nitrogen in 0–5 cm soil depth, and the increase in NTm was higher than that in NTc. But in 5–10 cm and 10–20 cm soil depth, no significant effect on soil organic carbon and total nitrogen was found in NT compared to CTr. From a soil profile view, soil organic carbon and total nitrogen decreased with increased soil depth. The results were similar with other studies (Gál et al., 2007; LópezFando and Pardo, 2009). Gál et al. (2007) found that soil organic carbon and total N in NT system greatly increased over CT in the upper 15 cm of surface but the effect sharply decreased with the increase in soil depth. López-Fando and Pardo (2009) indicated that soil N concentration and storage in soil surface 0–5 cm was higher after NT was conducted for 5 years than in CT but in the 10–20 or 20–30 cm depths soil N was significantly lower in NT than in CT. The increase in soil organic carbon and total nitrogen can be attributed to increased inputs of organic matter at the surface. Meanwhile,

NT decreased the contact of residue with soil microbes resulting in the slower decomposition, which will help NT sequester more soil organic carbon in soil surface (Chan et al., 2002). On the other hand, frequent and excessive tillage in CT did result in significant SOM loss. Furthermore, in our study, soil organic C increase in NTm plots was much more than that in NTc plots. Nayak et al. (2012) also observed the increase in SOC to be much higher with organic manure over with crop residue or green manure. Organic manures have already undergone some decomposition and organic C in these substances has already been converted to recalcitrant forms which allows for more C being sequestered in soil (Dick and Gregorich, 2004). Gong et al. (2009) also observed an increase in more stable C concentration for the manure addition and more labile C concentration for mineral fertilizer treatments. Tillage-induced changes in soil organic N are often directly related to changes in soil organic C (Zibilske et al., 2002).

4.3. Effects of tillage on weed populations This study found that tillage had no significant effects on weed density, but the trend was decreased flixweed density with NT. The reason was possibly that flixweed seed on the soil surface in NT systems may be more vulnerable to predation by rodents, soil fauna, and pathogens (Brust and House, 1988). NT significantly decreased the dry weight of flixweed, which indicated NTc or NTm inhibited their growth. Lower weed biomass and height recorded in NT in winter wheat cropping also indicated that NT affected weed growth. Chhokar et al. (2007) reported that NT decreased the Phalaris minor dry weight compared to CT with an average of 234.7 g/m2 in NT and 386.5 g/m2 in CT. This is mainly due to cultivated soil had a higher soil temperature, higher nitrogen content, better aeration, thereby providing a more favorable environment for weed growth and survival. Simultaneously, crop residues or cattle manure input in NT system can suppress weed establishment by altering environmental conditions related to germination, physically impeding seedling growth, and through allelopathic interactions (Crutchfield et al., 1986). Guo et al. (2007) indicated that some allelopathic substrate producing in the process of residue decompose could inhibit weed growth. However, Campbell et al. (1998) reported weed populations generally were not affected by tillage, but differed among N rate and placement treatments.

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In the study, fertilization had similar effects on density, dry weight and biomass of different weeds, e.g. SF promoted weed germination and growth. The biomass of flixweed was significantly different between fertilization treatments. The results indicated irrigation and fertilization in early growth stage of wheat promoted weed emergence and growth. Because weeds often germinate at the soil surface or near soil surface, especially under NT, while many agricultural weeds benefit from surface broadcast N or higher soil N levels (Blackshaw et al., 2005). Fertilization management of crop was an important component for weed management; however, the relationships among N placement, crop competition, environmental conditions and weed populations are not well understood and require further research. 5. Conclusions NT significantly reduced wheat biomass and grain yield after 2 years when it was conducted. The decrease in grain yield in NTm was lower than that in NTc thus manure may be a viable alternative to residue. Continuous NT for 4 years significantly increased the bulk density, pH, soil water content, soil organic C of the surface soil, but decreased the soil EC. The increase in soil organic C in NTm was higher than in NTc. Although soil EC decreased less in NTm than in NTc, the effects of soil EC could be neglected in the study. Flixweed was the dominant weed in the spring in wheat field, while NTc or NTm significantly inhibited the dominant weed in wheat field, thereby NT system might require lower rates of herbicide. The CF inhibited flixweed growth compared to the SF. Manipulation of crop fertilization should be considered an important component of weed management in NT system. It is clear that manure inputs are an excellent alternative to crop residue for NT in NCP, but long-term NT effects need further study. Considering the importance of food production in North China Plain, it is necessary to intensify the study of NT technologies in this region. Additional research is needed on NT planting (improving seed placement and germination), methods for preventing soil compaction, as well as residue and nitrogen fertilizer management in order to acquire higher and more sustainable yields. Acknowledgments This study was financially supported by the Strategic Science Plan of Institute of Geographical Sciences and Natural Resources Research (2012ZD004) and open foundation from Key International Collaboration Project of Ministry of Science and Technology of China (2004CB720501). Authors thank the anonymous reviewers for their constructive comments, which helped in improving the manuscript. References Agbede, T.M., Ojeniyi, S.O., 2009. Tillage and poultry manure effects on soil fertility and sorghum yield in southwestern Nigeria. Soil Till. Res. 104, 74–81. Blackshaw, R.E., Molnar, L.J., Larney, F.J., 2005. Fertilizer, manure and compost effects on weed growth and competition with winter wheat in western Canada. Crop Prot. 24, 971–980. Bremer, E., Kuikman, P., 1997. Influence of competition for nitrogen in soil on net mineralization of nitrogen. Plant Soil 190, 119–126. Brust, G.E., House, G.J., 1988. Weed seed destruction by arthropods and rodents in low-input soybean agroecosystems. Am. J. Altern. Agric. 3, 19–25. Campbell, C.A., Thomas, A.G., Biederbeck, V.O., McConkey, B.G., Selles, F., Spurr, D., Zentner, R.P., 1998. Converting from no-tillage to pre-seeding tillage: influence on weeds, spring wheat grain yields and N, and soil quality. Soil Till. Res. 46, 175–185. Chan, K.Y., Heenan, D.P., Oates, A., 2002. Soil carbon fractions and relationship to soil quality under different tillage and stubble management. Soil Till. Res. 63, 133–139. Chen, H., Bai, Y., Wang, Q., Chen, F., Li, H., Tullberg, J.N., Murray, J.R., Gao, H., Gong, Y., 2008. Traffic and tillage effects on wheat production on the Loess Plateau of China: 1. Crop yield and SOM. Aust. J. Soil Res. 46, 645–651.

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