利于水稻氮素吸收的绿肥翻压量和施氮水平研究

【目的】 紫云英是我国南方稻区重要的冬季绿肥，具有固定碳素、改善土壤物理性状、提高土壤养分含量等效果，能为后茬水稻提供良好的生长环境。本研究为探明水稻对氮素的吸收利用特性，为水稻高产栽培中氮肥的合理运筹和水稻氮素营养性状改良提供依据。 【方法】 在“紫云英–双季稻”耕作制度轮作土壤上，进行田间 4 × 4 双因素裂区试验。每小区收获的紫云英全部翻压为 100% 翻压，设不翻压、翻压 30%、60%、100% 4 个水平；每个翻压水平处理下，设置不施氮肥、施常规氮量 (N 150 kg/hm2) 的 30%、60% 和 100%，共 16 个处理。分别在分蘖期、孕穗期、抽穗期、灌浆期、成熟期取水稻植株样品，调查水稻氮素吸收利用特性。 【结果】 水稻群体干物积累量随生育进程处理间差异逐渐增大。抽穗期以 M_30% + N₀ 处理最高，M_60% + N_60% 处理次之，对照 (M₀ + N₀) 最低，此阶段是水稻群体物质积累量全生育期中差异最大的时期，最高的 M_30% + N₀ 处理较对照和其他处理平均高 79.02% 和 45.04%，此阶段的干物质积累量占总干物质积累量的比例为 23.19%～44.23%。分蘖期、灌浆期和成熟期干物积累量均以 M_60% + N_60% 处理最高，对照最低，在成熟期 M_60% + N_60% 处理群体总干物质重为 13.14 t/hm2，较对照高 53.15%。不同生育期水稻植株含氮量和吸氮量处理间不同。孕穗期、抽穗期和成熟期植株含氮量均以 M_60% + N_60% 处理最高，较其他处理平均分别高 20.71%、14.84% 和 15.44%；分蘖期、孕穗期、抽穗期和成熟期植株吸氮量也以 M_60% + N_60% 处理最高，对照最低，氮肥与冬种绿肥有显著协同效应。水稻氮素阶段吸收量及其占总吸收量的比例存在明显差异。分蘖期前、孕穗至抽穗期和抽穗至成熟期均是紫云英翻压 60% + 施氮 60% 处理的吸收量高于其他处理，平均分别高 29.89%、79.46% 和 121.1%；而分蘖至孕穗期是 M_100% + N_100% 处理达到最大，较其他处理平均高 51.87%。 【结论】 综合来看，供试条件下，在 “紫云英–双季稻” 种植体系中，M_60% + N_60% 处理能够提高氮肥利用效率，改善稻田氮素循环，对于实现水稻氮素高效吸收和利用具有重要意义。

Optimum combination of winter green manure plowed and nitrogen application levels for high nitrogen uptake and utilization in rice

Objectives]Milk vetch is an important winter green manure crop in the southern rice region of China, which can fix carbon, improve soil physical properties and increase soil nutrient contents. It could also provide a suitable environment for the succeeding rice crop. Characterization of nitrogen (N) uptake and use in rice could provide the basis for optimal N fertilizer application and for significant improvement in N nutrition for high-yield cultivation.Methods]Completely field experiments of 4 × 4 two-factor were performed continuously for four years in four different sites under milk vetch-double rice cropping system. The returning proportion of the whole harvested milk vetch was set at 0, 30%, 60% and 100%; in each returning level, 0, 30%, 60% and 100% of the conventional N fertilizer application rate (N 150 kg/hm2)in this region were set up to form 16 treatments in total and triplicate with each treatment. The N uptake in the tillering, heading, filling and maturity periods of rice was analyzed and N fertilizer use efficiency was calculated.Results]In the tillering, filling and maturity periods, the highest dry matter accumulation was all from the treatment of M60%+ N60%, and the lowest from M0N0, except that in the heading period the highest one was from M30%+ N0. With the growth elongation, the difference among the treatments in dry matter accumulation became large. At maturity, the highest population dry matter, weighed 13.14 t/hm2, was in the 60%M + 60%N, which was 53.15% higher than that in control. Also during these periods, the difference in dry matter accumulation of rice under different nitrogen application levels and winter green manure system was the greatest. Dry matter accumulation of M30%+ N0was 79.02% and 45.04%higher than that of M0N0and the average of all the other treatments, respectively. The ratio of dry matter accumulation to total dry matter in the heading to filling period ranged from 23.19%–44.23%. N content in rice plants was maximized in the booting, heading and maturity periods in treatment of M60%+ N60%, which was 20.71%, 14.84% and 15.44% higher than the average of other treatments, respectively. Correspondingly, the highest N uptake was in treatment of M60%+ N60%at tillering, booting, heading and maturity, and the lowest in control, N application and green manure showed significant synergy in N contents. Periodic N accumulation and its ratio in total N accumulation in treatment M60%+ N60%were significantly higher than all other treatments in the before tillering, booting-heading and heading-maturity periods. In the tillering-booting period, the periodic N accumulation was 51.87% higher in the treatment M100%+ N100%than the average of other treatments.Conclusions]Overall, the 60% of vetch plowed plus 60% of normal N application is effective in increasing N use efficiency and N recycling in the "milk vetch-double rice" system. Therefore, the combination should be recommended for achieving effective nitrogen uptake and utilization.