稻秸还田提高我国南方典型稻田冬绿肥产量和养分积累

  【目的】  提高冬绿肥的产量和养分积累量有利于轮作系统中主作物的高产稳产和光、温、养分资源的高效循环利用。研究稻秸还田对冬季豆科绿肥生长和养分积累及土壤性状的影响，为稻田豆科绿肥的高产栽培及稻秸资源化利用提供指导。  【方法】  在广西、四川和安徽，分别以盐渍水稻土、紫色土和黄棕壤为供试土壤，进行相同处理的豆科绿肥盆栽试验，供试品种均为当地主栽品种。稻秸添加量设 3个水平:0、3000、6000 kg/hm2 (S0、S1、S2)，每个稻秸添加水平下设两个施氮水平:0和45 kg/hm2 (N0、N45)，共包括6个处理。于豆科绿肥盛花期采集植株和土壤样品，测定鲜草产量和土壤理化性状。  【结果】  与稻秸不还田且不施氮肥处理(RS0N0)相比，盐渍水稻土、紫色土和黄棕壤上稻秸还田与氮肥配施处理的绿肥鲜草产量分别提高了63.0%～66.0%、35.2%～53.8%和103.6%～117.1%，植株氮累积量分别提高了19.1%～41.5%、43.7%～67.2%和65.1%～70.5%，磷累积量分别提高了12.1%～68.9%、31.4%～57.3%和37.9%～45.3%，钾累积量分别提高了22.0%～58.7%、30.7%～35.0%和89.2%～102.9%。在盐渍水稻土、紫色土，稻秸还田(S1、S2)均可提高绿肥鲜草产量和氮磷钾养分积累量，配合施氮没有进一步提高鲜草产量和氮磷钾养分积累量；而在黄棕壤与秸秆半量还田相比，稻秸全量还田降低了绿肥产量，但在一定程度上增加了绿肥地上部养分积累量，稻秸还田配合施用氮肥则显著增加了绿肥的产量和地上部养分积累量。盐渍水稻土稻秸还田与氮肥配施处理(RS1N45和RS2N45)提高了土壤有效磷含量；黄棕壤土壤有效磷含量、土壤速效钾含量随稻秸添加量增加先下降后上升，与不施肥对照相比，3种土壤上稻秸与氮肥配施处理均显著提高了土壤无机氮含量。偏最小二乘法路径模型分析表明，稻秸还田及土壤类型对豆科绿肥鲜草产量和地上部氮、磷、钾的累积量均有极显著正影响(P < 0.01)，氮肥处理仅对豆科绿肥鲜草产量有极显著正影响(P < 0.01)。  【结论】  稻秸还田不同程度地促进了豆科绿肥对土壤速效养分的吸收，提高了豆科绿肥鲜草产量和地上部氮磷钾累积量。在肥力较高的盐渍水稻土和紫色土上，稻秸全量还田可显著增加豆科绿肥的鲜草产量，维持土壤有效养分，无需配合施用氮肥。在肥力较低的黄棕壤上，全量还田(6000 kg/hm2)需配施氮肥才可充分发挥稻秸还田的增产效果，缓解土壤中有效养分含量的下降。

Returning rice straw to the field increased the yield and nutrient accumulation of green manure crops in a typical paddy field in South China

  【Objectives】  Returning leguminous green manure (GM) to the field promotes high and stable crop yield and sustainable agricultural development. Here, we studied the suitable patterns of returning rice straw to the field combined with chemical N fertilization for high growth and nutrient accumulation in GM planted during the fallow season in winter.  【Methods】  Pot experiments with the same treatments were conducted on salinized paddy soil in Guangxi, purple soil in Sichuan, and yellow-brown soil in Anhui. The three levels of rice straw turnover were 0, 3000, and 6000 kg/hm2 (S0, S1 and S2), and the N fertilization rates were 0 and 45 kg/hm2 (N0 and N45), giving a total of 6 treatments. At the full flowering stage of GM, the fresh biomass was harvested and weighed; the plant and soil samples were collected to determine plant nutrient accumulation and soil physical and chemical properties.  【Results】  Compared with no straw and no fertilization control, returning straw and N application increased the GM fresh yield by 63.0%–66.0%, 35.2%–53.8% and 103.6%–117.1%, N accumulation by 19.1%–41.5%, 43.7%–67.2% and 65.1%–70.5%, P accumulation by 12.1%–68.9%, 31.4%–57.3% and 37.9%–45.3%, K accumulation by 22.0%–58.7%, 30.7%–35.0% and 89.2%–102.9% in salinized paddy soil, purple soil, and yellow-brown soil, respectively. In salinized paddy soil and purple soil, returning rice straw (S1 and S2) increased the GM fresh yield and the accumulation of N, P, K, but the combined application of N fertilization did not improve them. In yellow brown soil, the total return of rice straw reduced the yield and nutrient accumulation of GM, and the return of rice straw combined with N fertilizer significantly increased the yield and nutrient accumulation of GM. In salinized paddy soil, RS1N45 and RS2N45 (P < 0.05) increased soil available P content. In yellow-brown soil, a higher straw rate resulted in higher soil pH, available K and P . In contrast, moderate straw rate (S1) resulted in the highest soil total N. According to the partial least squares path model analysis, returning straw and soil type had (P < 0.05) significant positive effects on the GM fresh yield and NPK accumulation. Conversely, N application only had a (P < 0.05) positive effect on GM fresh yield. Returning straw showed higher effects on GM fresh yield in salinized paddy and purple soil, while N application showed higher effects in yellow-brown soil.l least squares path model analysis, returning straw and soil type had (P < 0.05) significant positive effects on the GM fresh yield and NPK accumulation. Conversely, N application only had a (P < 0.05) positive effect on GM fresh yield. Returning straw showed higher effects on GM fresh yield in salinized paddy and purple soil, while N application showed higher effects in yellow-brown soil.  【Conclusions】  Returning straw and N application could increase the fresh yield and N, P, K accumulation in green manures and soil inorganic N content. In salinized paddy and purple soil, returning straw to the field could increase the yield and nutrient accumulation in leguminous green manure and maintain available soil nutrients without N application. In yellow-brown soil, returning the whole rice straw to the field should be combined with N application for sustainable yield and nutrient accumulation in green manure. This would also alleviate soil inorganic N and available P and K decrease.