西南喀斯特区坡耕地秸秆覆盖对土壤生态化学计量特征及产量的影响

土壤养分亏缺是限制作物生长的关键因素，同时也是制约作物产量的重要影响因子。为提高西南喀斯特区坡耕地土壤肥力和作物产量，于2018—2019年连续两年在贵州省黔西县开展了野外原位径流小区观测试验。通过该试验探讨不同秸秆覆盖率下土壤碳(C)、氮(N)、磷(P)、钾(K)含量及其生态化学计量特征，揭示不同秸秆覆盖率下土壤养分状况及土壤改良效果。共设6个秸秆覆盖梯度，玉米单作+秸秆覆盖(SM₀—SM₅,0,1111、2222、3889、5556,6944 kg/hm~2),其中SM₀为对照组(CK)。结果表明：(1)秸秆覆盖不同程度增加了土壤有机碳(SOC)、全氮(TN)及全磷(TP)含量，总体上随覆盖量的增加而增加，尤其是覆盖量较多的情况下(SM₄,SM₅),均显著高于对照(P<0.05),但两者之间差异不显著(P> 0.05),而全钾(TK)则随着覆盖量的增加而减少。(2)在高秸秆覆盖条件下(SM₄,SM₅),除了N∶P外，两...

Effects of straw mulching on soil ecological stoichiometry characteristics and yield on sloping farmland in karst area, Southwestern China

Soil nutrient deficiency is a key factor limiting crop growth and yield, but also threatens the survival of crops. In order to improve soil fertility and crop yield of sloping farmland in karst area of Southwestern China, the experiments were carried out in Qianxi county, Guizhou province for two consecutive years from 2018 to 2019. We explored the contents and the ecological stoichiometry characteristics of soil carbon, nitrogen, phosphorus, potassium and revealed the soil nutrient status and soil improvement effect under different straw mulching application rates through this experiment. There were six straw mulching gradients of maize monoculture+straw mulching (SM₀-SM₅, 0, 1111, 2222, 3889, 5556, 6944 kg/hm²), in which SM₀ was the control cheak (CK). The results showed that:(1) straw mulching increased the contents of soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) in different degrees, and generally increased with the increase of mulching rate. Especially in SM₄ and SM₅, which were significantly higher than those of the CK (P<0.05), but there was no significant difference between them (P > 0.05), while total potassium (TK) decreased with the increase of mulching rate. (2) Under the condition of high straw mulching (SM₄, SM₅), the stoichiometry ratio of soil nutrient elements in two years was significantly higher than that of the CK (P<0.05), except for N:P, but there was no significant difference between SM₄ and SM₅ (P>0.05). (3) Under the condition of straw mulching, the C:N and C:P in soil were lower, which accelerated the mineralization and decomposition of soil organic matter, and also showed that the availability of P was higher. (4) The crop yield of each mulching treatment was significantly higher than that of the CK (P<0.05), especially under the condition of high straw mulching, the yield of crop increased significantly, and the yield of SM₄ was the highest. The research showed that straw mulch on the ground is an important source of soil nutrients, which can be used as a supplementary means to supplement the soil nutrients absorbed by crops and lost with soil erosion. Based on the crop yield, the principal component analysis, grey correlation analysis, difference significance, it is suggested that straw mulching in about 6000 kg/hm² should be adopted for sloping farmland in the karst area of Southwestern China to promote the restoration of farmland ecosystem and achieve better effect of soil fertility and crop yield.