Elsevier

Soil and Tillage Research

Volume 163, November 2016, Pages 207-213
Soil and Tillage Research

Crop yield and soil carbon responses to tillage method changes in North China

https://doi.org/10.1016/j.still.2016.06.005Get rights and content

Highlights

  • Effects of 10 years conservation tillage plus 4 years deep tillage experiments were investigated in North China.

  • Crop yield and soil carbon were significant changed by conservation tillage conversion to deep tillage.

  • Deep tillage increased crop yields by 35, 24 and 24% compared with no tillage, rotary tillage and harrow tillage.

  • Deep tillage altered SOC pools by −1.5, 15.6 and 13.2 Mg ha−1 compared with no tillage, rotary tillage and harrow tillage.

Abstract

Subsoil compaction at 15–30 cm depths due to the increase of bulk density or decrease in porosity after long-term no tillage or reduced tillage (e.g. rotary tillage or harrow tillage) is of growing concern. Deep tillage is generally regarded as an important method to reduce subsoil compaction due to long-term conservation tillage and thereby improve crop production and soil conditions. We compared the responses of crop yield and soil carbon (C) among 10-year no tillage (NT), rotary tillage (RT), and harrow tillage (HT) treatments, and their conversions to deep tillage (DT) for 4 years involving NT-DT, RT-DT and HT-DT treatments. The soil organic carbon (SOC) pool under the NT treatment was 29 and 91% higher than the SOC pools of the HT and RT treatments, respectively, whereas the NT annual yield decreased by 0.6 Mg ha−1 yr−1 over 10 years. The NT-DT, RT-DT and HT-DT treatments increased crop yield by 35, 24 and 24% and altered the SOC pool by −1.5, 15.6 and 13.2 Mg ha−1 over the 4 years of deep tillage compared with the corresponding values for NT, RT, and HT, respectively. Therefore, conversion to DT after long-term NT, RT, and HT use can benefit crop yield and play an important role in improving soil carbon sequestration following the long-term adoption of RT and HT systems in North China.

Introduction

Achieving food security is an urgent, high-priority issue in China (Chen et al., 2011a). As a result, the continuous improvement of crop yield is a prominent goal in agricultural research. Mitigating and preventing further soil degradation due to erosion and soil organic carbon (SOC) loss are crucial for accomplishing this goal. Conservation tillage, which is generally defined as minimal soil disturbance resulting in a residue retention of at least 30% (Zhang et al., 2005), is becoming an economical and ecologically viable option for conserving energy and providing favorable soil conditions for sustainable crop production, soil carbon (C) sequestration, and efficient nitrogen fertilizer use (Mazzoncini et al., 2011, Chen et al., 2011b, Pramod et al., 2012). Currently, conservation tillage is used on 11% of the total global agricultural cropland (FAO, 2010). In China, the area under conservation tillage increased to 8.5 Mha in 2011, equivalent to 4.7% of the total agricultural cropland (Geng, 2012), and most of them use wheat-maize double cropping system in silt loam soils under temperate monsoon climates in the North China (Zhang et al., 2014).

Harrow tillage (HT), rotary tillage (RT) and no-tillage (NT) are frequently used to mitigate soil erosion and loss of SOC in North China (Zhang et al., 2005). However, after several successive years of these reduced tillage (i.e., only tilling to a depth less than 20 cm) or no-tillage systems, subsoil compaction at 15–30 cm depths appears to be increasing due to the increase of bulk density resulted by water infiltration and sowing and harvesting machineries (Kong et al., 2010, Wang et al., 2014). Furthermore, although adopting some form of conservation tillage is generally beneficial for increasing SOC levels and sequestering C in the topsoil (Ussiri and Lal, 2009, Martinez et al., 2013), the reduced incorporation of crop residues has been reported to increase subsoil bulk density and reduce crop root proliferation (Figuerola et al., 2012), thereby limiting water and nutrient availability (He et al., 2009) and resulting in reduced crop yields (Bhatia et al., 2010, Arvidsson et al., 2014). For example, many studies have demonstrated that decreases in crop yield in response to long-term NT adoption may be caused by reduced seed germination and emergence, lower early season soil temperatures, below-optimal plant populations, poorer weed control, delayed plant development and maturity, increased grain moisture content, and lower grain yield potential following adoption of NT (Toliver et al., 2012, Kovar et al., 1992, Fortin, 1993, Swan et al., 1994). Therefore, understanding the responses of SOC and crop yield to long-term conservation tillage is very important in China because achieving sustainable high yields and soil quality is a fundamental precondition for adopting conservation tillage.

Deep tillage (DT) to a depth more than 30 cm is an effective method to break up compacted subsoil layers and decrease soil bulk density (He et al., 2007, Hou et al., 2012). It has positive effects on soil structure, soil C sequestration, and crop yield in North China (Huang et al., 2006, Wang and Li, 2014, Xu et al., 2015). A previous study has demonstrated the bulk density was decreased by 8.7–11.8% and significant increased soil total porosity of the 10–40 cm layers after the long-term conservation tillage conversion to DT (Nie et al., 2015), which played an important role for the disruption of the compacted zone. However, the effects of tillage conversion on crop productivity and the SOC pool were unknown. Therefore, our objectives were to (1) quantify crop yield and SOC responses to 10-year HT, RT, and NT treatments and (2) determine how the conversion of these three conservation tillage methods to DT affected yield and SOC following the first 4 years after conversion to deep tillage.

Section snippets

Experimental site

The study site was located at Tai’an (North China, 36°09′N, 117°09′E), which typifies the soils and temperate continental monsoon climate of North China. The average annual precipitation and annual temperature were 710 mm and 13.8 °C, respectively, during the experiment. The soil is classified as Udolls according to the USDA Soil Taxonomy System (Soil Survey Staff, 1998). The soil texture is 40% sand, 44% silt and 16% clay. At the start of the experiment in 2002, the soil in the 0–30 cm layer had

Long-term conservation tillage effects on crop yield

Wheat and maize yields showed the largest decline with time under NT compared with the HT and RT treatments (Fig. 2a and b), although the HT and RT yields also generally decreased over time. The wheat yields under the HT, RT and NT treatments decreased by an average of 34, 31 and 52%, respectively, from 2005 to 2012. Maize yields showed similar declines, averaging 20, 16 and 24% decreases, respectively. The annual total yield of the wheat and maize production systems also decreased over the

Discussion

After the long-term adoption of NT, crop yield has been observed to decrease, remain unchanged, or increase only in the first several years in many regions (Powlson et al., 2014). Our study found that wheat and maize yields decreased in three conservation tillage treatments during 2005–2012, especially under the NT treatment, which produced the lowest annual yield. Similar trends have been reported in other studies (Soane et al., 2012, Gruber et al., 2012). However, many other studies have

Conclusions

In the present study, yield decreases were observed after the long-term use of 3 conservation tillage systems, including NT, HT, and RT. In addition, a negative effect of the RT treatment on soil C sequestration was observed, whereas the NT treatment was beneficial to C sequestration. The conversion of these long-term conservation tillage treatments to DT, i.e., NT-DT, HT-DT and RT-DT, resulted in significant improvements in the annual total yield of wheat and maize cropping system. Although

Acknowledgements

We appreciate the funding for this project awarded by the Natural Science Foundation of Shandong Province, China (ZR2015CQ007), the Youth Scientific Research Foundation of Shandong Academy of Agricultural Sciences (2015YQN37), the Special Research Funding for Public Benefit Industries (Agriculture) of China (201503121), and the National Science and Technology Research Projects of China (2012BAD14B07).

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