Effect of Straw Returning Mode on Soil Organic Carbon Sequestration

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the National Key R&D Program (No. 2016YFD0200308), Key Research and Development Program of Shaanxi (2019ZDLNY01-05-01) and the Key Technologies R&D Program of China during the 12th Five-Year Plan period (No. 2012BAD14B11)

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    [Objective] Aiming at overcoming the shortcomings of direct application of crushed straw into the soil under the wheat-maize rotation system, a years-long field experiment was carried out in an attempt to screen out an optimal mode for straw returning that could meet the targets of high yield, cost saving and soil fertility improvement.[Method] The nearly 10 years of field experiment on returning of wheat-maize straw was designed to have four treatments or straw returning modes, namely, (i)no return of either wheat or maize straw (WN-MN, CK1); (ii) return of wheat and maize straw, both crushed (WC-MC, CK2); (iii)leaving high wheat stubblein the field (WH-MN); and (ⅳ)leaving high wheat stubble and returning crushed maize straw (WH-MC). By comparing the treatments in the yield, gain and loss of soil organic carbon stock, carbon pool management index and other indices, advantages and disadvantages of the treatments were analyzed.[Result] Results show that Treatment of WC-MC and WH-MC was 81% and 243%, respectively, higher than the other two treatments (WH-MN, WN-MN). and 24.23% and 16.05%, respectively, higher than Treatment WN-MN in SOC stock. Compared with the SOC stock of the soil prior to the experiment, carbon sequestration of the four treatments varied in the range of -0.83~6.14 Mg·hm-2. Both sequestered C and non-sequestered C were positively related to cumulative carbon input, indicating that high-amount straw returning is more conducive to carbon sequestration. The minimum carbon input to maintain the basic organic carbon balance was 4.06 Mg·hm-2·a-1. The labile fraction of SOC (LFSOC)in each treatment decreased with the increase in soil depth. Compared with Treatment WN-MN, Treatment WC-MC, WH-MC and WH-MN increased LFSOC content in the 0~20 cm layer. Among them, the labile fraction of SOC (active organic carbon, dissolved organic carbon, microbial biomass carbon, hot water soluble carbon and particulate organic carbon)was the highest in Treatment WC-MC, and then in Treatment WH-MC, both of which were significantly higher than the other two (WH-MN and WN-MN). Treatment WH-MN was 35.7%, 21.4%, 34.1%, 24.2% and 36.8% higher than Treatment WN-MN in content of LOC, DOC, MBC, HWC and POC. The five components varied in the range of 35.5%-64.3%, 21.4%-55.3%, 34.1%-58.7%, 22.7%-42.9%, and 36.7%-60.7%, respectively, in sensitivity index (Table 3) and between the treatments, with Treatments WC-MC and WH-MC being significantly higher than Treatments WN-MN. Treatments WC-MC and WH-MC were also significantly higher in carbon management index than CK in each soil layer. In the season of 2015-2016, Treatment WC-MC and WH-MC was 34.5% and 20.1%, respectively, higher than Treatments WH-MN and WN-MN in annual crop yield, and in the season of 2016-2017, Treatmentl WH-MC wasthe highest or 11.1% higher on average than the three treatments. Moreover, in the season of 2015-2016 annual crop yield was found to be significantly and positively related to SOC and C inputs, but in the season of 2016-2017. it was not.[Conclusion] So in view of its effects SOC stock, LFSOC, CPMI, crop yield and saving cost, the mode of returning of crushed maize straw plus 25-30 cm long stubble left in the field for maize cultivation is deemed as an optimal straw-returning strategy for sustainable development of the agriculture under the intensive maize-wheat rotation system in Guanzhong Plain.

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ZHAO Huili, DONG Jinjin, SHI Jianglan, XU Miao, TIAN Xiaohong. Effect of Straw Returning Mode on Soil Organic Carbon Sequestration[J]. Acta Pedologica Sinica,2021,58(1):213-224.

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  • Received:September 02,2019
  • Revised:December 02,2019
  • Adopted:January 11,2020
  • Online: October 30,2020
  • Published: January 11,2021