耕作方式和秸秆还田对砂姜黑土碳库及玉米小麦产量的影响

长期秸秆还田免耕覆盖措施导致沿淮区域砂姜黑土耕层变浅、下表层(10～30 cm)容重增加、土壤养分不均衡等问题凸显,限制了小麦-玉米周年生产力的提高。耕作和秸秆还田措施合理的搭配组合是解决这一问题的有效方法。通过8年的小麦-玉米一年两熟田间试验,设置4个处理:1)玉米季免耕-小麦季免耕秸秆不还田(N);2)玉米季深耕-小麦季深耕秸秆不还田(D);3)玉米季秸秆免耕覆盖还田+小麦秸秆免耕覆盖还田(NS);4)玉米季秸秆免耕覆盖还田+小麦季秸秆深耕还田(DS)。通过分析作物收获后不同土壤深度(0～60 cm)总有机碳(TOC)、颗粒态碳(POC)、微生物生物量碳(MBC)、易氧化态碳(KMnO4-C)、可溶性有机碳(DOC)和土壤碳库管理指数(CPMI),并结合小麦-玉米的周年产量变化,以期获得培肥砂姜黑土的最佳模式。研究结果表明:1)相对于长期免耕措施(N),DS处理能够提高0～30 cm土层TOC、POC、MBC、KMnO4-C等组分含量和CPMI;而NS措施仅提高土壤表层(0～10 cm)TOC、活性有机碳组分含量和CPMI;2)DS处理显著提升了小麦-玉米的周年生产力,其麦玉的周年产量均值分别比N、D和NS处理高出14.7%、12.9%和8.5%;3)MBC和KMnO4-C对于耕作和秸秆还田措施都是较为敏感指示因子。总的来说,玉米季小麦秸秆覆盖还田+小麦季玉米秸秆深耕还田(DS)是改善沿淮地区砂姜黑土土壤碳库、提高小麦-玉米周年产量的一种有效农田管理模式。

Influence of tillage and straw retention on soil carbon pool and maize-wheat yield in Shajiang black soil

Long-term no-tillage mulching with straw retention have led to the shallowness of plough layer, the increase of bulk density at the depth of 10-30 cm layer, and the imbalance of soil nutrients in Shajiang black soil along Huai River, which have limited the improvement of productivity of summer maize (Zea mays) and winter wheat (Triticum aestivum). Tillage practice and residue management play important roles in carbon pool and crop yields in soils. The reasonable combination of tillage with straw retention is an effective method to solve this problem. After 8-years field experiment in wheat - maize cropping systems, four treatments were set up, 1) no-tillage with straw removal for summer maize and winter wheat (N); 2) tillage with straw removal for summer maize and winter wheat (D); 3) no-tillage with straw mulching for summer maize and winter wheat (NS); and (4) no-tillage with straw mulching for summer maize and plough tillage with straw incorporation for winter wheat (DS). Soil samples were taken from the 0-10, 10-20, 20-30, 30-40, 40-50 cm and 50-60 cm soil depths. Soil total organic carbon (TOC), particulate organic C (POC), microbial biomass C (MBC), potassium permanganate-oxidizable C (KMnO4-C) and dissolved organic C (DOC) were measured. Carbon pool management index (CPMI) was also calculated. These indexes and the year-round yield of maize and wheat were comprehensively analyzed to gain the optimal mode for enriching the Shajiang black soil. Our tesults showed that DS treatment increased the contents of TOC, POC, MBC, KMnO4-C and CPMI at the depth of 0-30 cm layer, compared with N treatment, but NS treatment only enhanced the contents of above-mentioned indexes at the depth of 0-10 cm layer. The tillage operation incorporated the maize residue (straw, stubble, and root) to a greater soil depth in DS treatment, which meant that DS had a higher subsoil TOC, POC, MBC, KMnO4-C and CPMI content (10-30 cm) than the other treatments. There were no significant (P<0.05) differences in TOC, POC, MBC, KMnO4-C contents in the 30-60 cm layers among the four treatments. In addition, the total yields for summer maize and winter wheat in four treatments fluctuated widely from year to year. Treatment DS significantly (P<0.05) inceased the year-round crop yield, and the mean crop yield of DS was 14.7%, 12.9% and 8.5% greater than that of N, D and NS over 8 years. Moreover, microbial biomass carbon and KMnO4-C was significantly (P<0.05) affected by the tillage and straw retention and was sensitive to different management practices. Total organic carbon was positively correlated with MBC and KMnO4-C, suggesting they were suitable as an early indicator of soil quality. The significant crop yield improvement observed in DS was attributed to the combined effect of tillage practice and crop residue management on improving the soil fertility and enhancing the labile carbon pool in the Shajiang black soil, which promoted the growth of summer maize and winter wheat. Generally, treatment DS was an sustainable and effective management practice to improve the soil carbon pool and enhance the year-round yield of summer maize and winter wheat in Shajiang black soil along Huai River.