Elsevier

European Journal of Agronomy

Volume 63, February 2015, Pages 47-54
European Journal of Agronomy

Integrative effects of soil tillage and straw management on crop yields and greenhouse gas emissions in a rice–wheat cropping system

https://doi.org/10.1016/j.eja.2014.11.005Get rights and content

Highlights

  • Straw incorporation increases wheat yield but not rice yield.

  • Rotary tillage increases CH4 emissions regardless of straw practices.

  • Plowing with rotary tillage benefits crop yielding with less GHG emission.

Abstract

Significant efforts have been made to assess the impact of tillage regimes on crop yields and/or greenhouse gas (GHG) emissions across single crop growing season. However, few studies have quantified the impact across a whole rotation cycle in multiple cropping systems. Utilizing on a long-term tillage experiment with the rice–wheat rotation system in East China, we examined the GHG emissions under different tillage practices with or without crop straw incorporation. Results showed that compared to the no-straw control, straw incorporation increased wheat yield by 28.3% (P < 0.05), irrespective of tillage practices, but had no significant effect on rice yield. Although straw incorporation did not significantly affect CH4 emissions during the wheat season and N2O emissions during the whole rice–wheat cycle, it significantly stimulated CH4 emissions by 98.8% (P < 0.01) during the rice season. Also, there were no significant differences in CH4 and N2O emissions between tillage practices during the wheat season. Compared to plowing, rotary tillage increased CH4 emissions significantly by an average of 38.8% (P < 0.01) but had no significant impacts on N2O emissions during the rice season. Across the rotation cycle, annual yield-scaled global warming potential of CH4 and N2O emissions under no-tillage plus rotary tillage was 26.8% (P < 0.01) greater than that of rotary tillage plus plowing with or without straw incorporation. Significant interactions between soil tillage and straw management practices were found on annual GHG emissions, but not on crop yields. Together, these results indicate that plowing in the rice season plus rotary tillage in the wheat season may reduce GHG emissions while increasing crop yield in rice–wheat cropping areas.

Introduction

Soil tillage and straw management can alter carbon (C) and nitrogen (N) dynamics and consequently induce considerable changes in greenhouse gas (GHG) emissions and crop productivity (Paustian et al., 1997, Lal, 2004, Smith et al., 2008, Liu et al., 2014). For example, straw incorporation can stimulate GHG emissions through increasing C availability for methanogenics in paddy soils (Yan et al., 2005) and denitrifiers in dry-land soils (Luo et al., 1999). Also, in comparison to conventional tillage, no-tillage, and reduced tillage can enhance soil C sequestration by decreasing soil C decomposition and/or C turnover, thereby mitigating GHG emissions (Six et al., 2000, Al-Kaisi and Yin, 2005, Van Grogenigen et al., 2011, Ruan and Philip Robertson, 2013). Furthermore, reduced tillage and straw incorporation alone or in concert can improve crop yields through improving soil fertility (Malhi and Lemke, 2007, Küstermann et al., 2013).

Rice–wheat rotation system is the most popular cropping system in East Asia, covering ca. 13 million hectares each year in China (Frolking et al., 2002). Because this system consists of both irrigated rice and dry-land wheat, it raises unique challenges for quantifying the total GHG emissions. Agricultural practices, such as soil tillage and straw incorporation management, play an important role on crop productivity and/or GHG emissions (Ma et al., 2009, Pandey et al., 2012, Yao et al., 2013, Brennan et al., 2014). Therefore, it is imperative to assess the impact of agricultural practices on crop yields and GHG emissions and determine the mitigation potential management practices for agronomic innovations.

There are an increasing number of studies assessing soil tillage and straw management effects on GHG emissions and/or crop productivity in rice–wheat cropping areas. However, most of them have only considered single cropping season (Zou et al., 2005, Gangwar et al., 2006, Yao et al., 2009) and few have quantified the impact across a whole rotation cycle where multiple cropping is involved. For example, Zou et al. (2005) reported that straw incorporation increased CH4 emission and reduced N2O emission in the rice season. But Yao et al. (2009) showed that straw incorporation decreased N2O emission in the non-rice season. Also, reduced tillage perturbations were found to reduce CH4 and N2O emissions and grain yield (Pandey et al., 2012). To date, there are still many uncertainties about the effects of soil tillage and straw management practices on crop yields and GHG emissions. One of the main reasons might be due to the experimental duration, as most of existing studies were based on very short-term experiments (Ma et al., 2009, Yao et al., 2013). Yet effects of soil tillage and straw management practices on soil C storage and GHG mitigation are complex and may vary with practice duration (Duiker and Lal, 1999, Six et al., 2004, Smith et al., 2008). Also, it is worthy to mention that soil tillage and straw management practices are often intermingled together in field. However, existing field studies have mainly determined the effects of either tillage or straw management practices and the interactions of these two practices are not well documented (Bayer et al., 2014). Therefore, it is essential to further quantify the long-term effects of soil tillage and straw management on crop yields and GHG emissions across a whole rotation cycle in multiple cropping systems.

The objective of this study was to assess the effects of soil tillage and straw management on CH4 and N2O emissions and crop yields in the rice–wheat rotation system. Year-round measurements of CH4 and N2O emissions were conducted in an existing long-term field experiment to assess the net effect across the whole rotation cycle. Also, field soils were obtained from these long-term plots and incubated to estimate soil C and N mineralization under simulated soil tillage and straw management practices.

Section snippets

Experimental site description

Our field measurements of CH4 and N2O fluxes were conducted with the long-term tillage experiment located at the Institute of Agricultural Sciences in Taihu Lake District, Wuxi city (31°27′N, 120°25′E), Jiangsu Province, China. The Taihu region represents a northern subtropical monsoon climate with an annual temperature of about 15.7 °C, an average annual precipitation of 1094 mm, and the effective accumulated temperature (above 10 °C) of 4947 °C. The soil has a clayey loam, developed from loessial

CH4 fluxes and seasonal/annual cumulative emissions

During both rice seasons, CH4 fluxes were the highest right after transplanting (7 days) across all treatments and remained relatively high for another 3–4 weeks (Fig. 1a). CH4 fluxes decreased quickly after week 5 and remained at a low level since. The highest CH4 fluxes ranged from 391 to 1667 mg CH4single bondC m−2 d−1, and from 314 to 1933 mg CH4single bondC m−2 d−1 in 2011 and 2012, respectively. Averaged cumulative CH4 emissions were 3457 and 6872 kg CO2eq ha−1 for the non-straw and straw incorporated treatments,

Effects of soil tillage and straw incorporation on CH4 emission

Our results showed that straw incorporation can have significantly different effects on CH4 emissions between rice and wheat growing seasons (Fig. 1; Table 2). These differences likely stem from the resulting impacts of different management regimes on soil C and O2 for methanogens. Two pathways of CH4 production contribute to CH4 emissions in rice paddies. Acetotrophy process (C6H12O6 3CO2 + 3CH4) is considered to be the dominant process, contributing about 2/3 of the CH4 produced (Segers, 1998,

Conclusions

Our assessment of GHG emissions and crop yields across the whole rotation cycle showed different a picture from results either from the rice or wheat season alone. Also, trade-off occurred between crop yield and CH4 emissions as influenced by soil tillage and straw incorporation management practices. Based on annual GWP and crop yield analyses, tillage regimes of rotary tillage in the wheat season followed by plowing in the rice season, irrespective of straw management was an optimum practice

Acknowledgements

This work was supported by the National Key Technology Support Program of China (2011BAD16B14), the Program for New Century Excellent Talents in University (NCET-05-0492), the GEF Project of Climate Smart Staple Crop Production in China (P144531), the Innovation Program of CAAS and the grant of China Scholarship Council (CSC).

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