基于15N研究红壤地“黑麦草+甜玉米║大豆”种植模式中甜玉米氮肥高效利用机制

The“cover crop+cereal-legume”cropping system is conducive to increase crop diversity, keep high quality and yield of crop, improve soil fertility, and reduce the input of chemical fertilizer to maintain soil health. It corresponds to the state strategy of “Zero growth in chemical fertilizer application” and “Rotation fallow”. According to the previous work, the study is based on the abundant light and temperature resources in the hilly red soil region of southern China, and comprehensively utilizes the combined advantages of the cover crop and the cereal-legume intercropping system.Through microplot field experiment, the 15N isotope-labeled urea was used to quantitatively study the contribution of planting ryegrass to utilization of nitrogen fertilizer by sweet corn in the cropping system of "ryegrass + sweet corn-soybean", and comprehensively analyzed the correlations between the chemical nitrogen use efficiency of sweet corn, soil nitrogen and soil nitrogen related microbial community. Clarify mechanism of sweet corn chemical nitrogen utilization was improved by planting ryegrass in red soil.The entire project tried to quantify the chemical nitrogen utilization of sweet corn in the “ryegrass+sweet corn-soybean” cropping system, scientifically and rationally reduce chemical nitrogen input, decrease production costs and environmental pollution. It provides theoretical basis and technical support for the coordinated development of high quality, high yield and farmland environmental protection in southern sweet corn.

“覆盖作物+禾本科║豆科”种植模式有利于增加作物多样性，维持作物优质高产，改善土壤肥力，同时还能减少化学肥料投入，维持土壤健康，契合国家化肥使用量零增长和轮作休耕战略。本研究在前期工作基础上，立足南方红壤丘陵区丰富的光温资源，综合利用覆盖作物和禾本科║豆科间作的联合优势，通过大田微区试验，利用15N同位素标记的尿素定量研究“黑麦草+甜玉米║大豆”种植模式中黑麦草种植对甜玉米吸收利用上茬氮肥的贡献，综合分析甜玉米氮肥利用效率与土壤氮素和氮相关土壤微生物群落组成的相关关系，阐明红壤地种植黑麦草改善甜玉米的氮肥吸收利用的机制。整个项目通过定量“黑麦草+甜玉米║大豆”种植模式中甜玉米氮肥利用量，科学合理减少化学氮肥投入，降低生产成本和环境污染，为南方甜玉米优质高产与农田环境保护协调发展提供一定的理论依据和技术支持。

本项目基于15N示踪技术在江西农业大学农业科技园开展了2年（2020-2021）的田间微区试验，研究了“黑麦草-甜玉米||大豆”种植模式中作物氮累积、作物氮肥吸收利用效率、黑麦草对下年作物氮素利用的贡献、土壤养分和土壤微生物群落组成。主要结果如下：（1）冬种黑麦草有提高下年甜玉米和大豆氮累积量的趋势。（2）冬种黑麦草有增加下年甜玉米和大豆化学氮肥吸收利用效率的趋势。甜玉米的化肥氮吸收利用效率显著高于大豆，春季甜玉米对化肥氮的吸收利用效率高于秋季甜玉米。（3）黑麦草吸收累积的化肥氮有50.66%能被下年作物（甜玉米和大豆）吸收利用，黑麦草对下年作物氮素利用贡献率超过100%。（4）冬种黑麦草有降低土壤pH、碱解氮和硝态氮的趋势。相比于冬闲，冬种黑麦草显著降低了2021年秋季甜玉米收获期土壤碱解氮、硝态氮和铵态氮含量。（5）冬种黑麦草有明显降低甜玉米收获期土壤微生物基因预测数量和总碱基数，分别降低了21.07%和24.62%。黑麦草对甜玉米收获期土壤微生物物种种类和功能基因组成没有显著影响。综合来看，冬种黑麦草有利于提高甜玉米||大豆种植模式的作物化肥氮利用效率，黑麦草翻压腐解有利于提高下茬作物的氮素累积量，降低土壤无机氮含量，保护农田生态环境。试验结果为进一步研究冬季覆盖作物（黑麦草）来进行合理减氮，实现节本增收提供了一定的参考依据。