豫南紫云英水稻轮作区减施不同比例氮肥对水稻养分吸收和转运的影响

  【目的】  研究水稻–紫云英轮作体系中，翻压紫云英并减施氮肥对不同生育期水稻养分吸收、转运特征，以及对土壤养分状况的影响，为豫南稻区紫云英–水稻轮作模式氮肥的科学管理提供理论依据。  【方法】  长期定位试验位于河南信阳，始于2008年。试验设置不施肥对照(CK)、常规施肥(N100)，以及种植并翻压紫云英条件下，氮肥为常规处理用量的100% (GN100)、80% (GN80)、60% (GN60)、40% (GN40)，共6个处理。测定了水稻产量、关键生育期生物量、氮磷钾养分吸收量、土壤基础养分含量，分析了水稻养分吸收及土壤养分供应对水稻产量的影响。  【结果】  与N100处理相比，GN40、GN60、GN80和GN100处理水稻产量无显著差异，GN40和GN60处理氮肥农学效率分别增加213.41%和113.70%，GN40、GN60和GN80处理氮肥偏生产力分别增加162.17%、75.69%、34.39%。与N100处理相比，GN100和GN80处理抽穗期秸秆生物量分别增加17.22%和41.06%，成熟期秸秆生物量分别增加28.22%和20.92%。与N100处理相比，GN60、GN80和GN100处理成熟期稻谷氮吸收量分别增加31.34%、31.79%和20.13%，GN60、GN80成熟期稻谷磷吸收量分别增加14.23%和14.61%，GN80处理成熟期稻谷钾吸收量增加10.64%。与N100处理相比，GN60处理氮转运量增加12.54 kg/hm2；GN40、GN60和GN80处理磷转运量分别显著增加11.32、23.02和18.09 kg/hm2，磷转运率分别增加35.92、41.22和39.91个百分点，磷对稻谷转运贡献率分别增加39.36、74.60和57.93个百分点。与N100处理相比，GN40、GN60、GN80和GN100能充分满足水稻生长过程中对土壤无机氮需求；GN60、GN80处理分蘖期、拔节期和抽穗期土壤有效磷含量显著降低；GN40、GN60、GN80和GN100处理分蘖期、抽穗期和成熟期土壤速效钾含量显著降低。随机森林分析结果表明各生育期土壤有效磷含量和水稻分蘖期氮、磷、钾吸收量对水稻产量形成有较大的贡献。线性回归分析表明，分蘖期和抽穗期土壤养分含量以及各生育期地上部氮、磷、钾吸收量与稻谷产量呈显著正相关。  【结论】  在我国豫南紫云英–水稻轮作区，翻压紫云英配合氮肥减施40%，能够培育土壤碳、氮库，满足土壤氮素供应，促进水稻对磷、钾养分的吸收和积累，增加籽粒氮、磷、钾养分转运量，提高氮肥农学效率和偏生产力，实现水稻增产稳产。

Nutrient absorption and transport characteristics of rice under different nitrogen reduction ratios in a Chinese milk vetch and rice rotation system in southern Henan Province,China

  【Objectives】  Chinese milk vetch (CMV) and rice rotation is a common cropping system in south Henan rice production area. We studied the nutrient absorption and transport characteristics of rice, and the soil nutrient supply capability under the condition of incorporating all CMV and reducing different proportion of nitrogen fertilizer input, to provide a theoretical basis for N fertilizer management in the rotation system.  【Methods】  The long-term CMV and rice rotation experiment was established in Xinyang, Henan Province in 2008. Six treatments were included - no fertilization (CK), conventional fertilization without burying CMV (N100), and burying fresh CMV before rice transplanting, and conventional N rate of 100%, 80%, 60%, and 40% (GN100, GN80, GN60 and GN40). The rice yield, biomass, N, phosphorus (P), and potassium (K) nutrient absorption and basic soil nutrients at different stages were measured.   【Results】  There was no significant difference in rice yield among N100, GN40, GN60, GN80, and GN100 treatments, while GN40 and GN60 treatments increased agronomic efficiency of N fertilizer by 213.41% and 113.70% compared with N100; GN40, GN60, and GN80 treatments increased N partial productivity by 162.17%, 75.69%, and 34.39%, respectively. Compared with N100 treatment, GN80 and GN100 treatments straw biomass increased by 41.06% and 17.22% at heading stage and by 28.22% and 20.92% at maturity stage, respectively. GN60, GN80, and GN100 treatments increased N absorption in grain by 31.34%, 31.79%, and 20.13%; GN60 and GN80 treatments increased P absorption in grain by 14.23% and 14.61%, respectively; GN80 treatment increased K absorption in grain by 10.64% at the maturity of rice. Compared with N100 treatment, GN60 treatment increased N transport capacity by 12.54 kg/hm2; GN40, GN60, and GN80 increased P transport capacity by 11.32 kg/hm2, 23.02 kg/hm2 and 18.14 kg/hm2; P transport rate by 35.92, 41.22, and 39.91 percentage points; P contribution rate to grain was increased by 39.36, 74.60 and 57.93 percentage points, respectively. Compared with N100 treatment, GN40, GN60, GN80, and GN100 treatments met the sufficient supply of soil mineral nitrogen during rice growth. GN60 and GN80 treatments significantly reduced the content of soil available P at tillering stage, jointing stage and heading stage; GN40, GN60, GN80, and GN100 treatments significantly decreased the content of soil available K at tillering stage, booting stage and maturity stage, respectively. The random forest analysis showed that soil available P at each growth stage and N, P, and K absorption at rice tillering stage had a great contribution to rice yield. Linear regression analysis revealed that soil nutrient at tillering stage and booting stage of rice and aboveground N, P, and K absorption at each growth stage of rice were significantly and positively correlated with rice yield.   【Conclusions】  Under the CMV and rice rotation system in southern Henan Province, reducing 40% of conventional chemical N input improves the soil N and carbon pool storage, stimulates the absorption and transport to grain of NPK, keeps rice yield stable, and improves the agronomic efficiency and partial factor productivity of N fertilizer.