赣北地区稻−稻−紫云英轮作体系减施化肥对水稻产量、氮素吸收及土壤供氮能力的影响

Yield and nitrogen uptake of rice and soil nitrogen supply capacity under fertilizer reduction in a rice-rice-Chinese milk vetch rotation system, northern Jiangxi Province, China

【目的】紫云英与水稻轮作是合理利用冬闲稻田,维持和提高稻田生产力的高效手段。研究稻–稻–紫云英模式下,减施化肥对水稻产量、氮肥利用效率、氮素吸收量和土壤供氮能力的影响,为赣北双季稻区减施化肥提供理论依据。【方法】定位试验位于江西省高安市,始于2016年,试验设置不施肥对照(CK)、常规施肥(F100),以及种植翻压紫云英条件下,晚稻季正常施肥,早稻化肥为常规施肥的100%、80%、60%、40%(GF100、GF80、GF60、GF40),共6个处理。在早稻分蘖期、拔节期、抽穗期和成熟期及晚稻成熟期,采集植株(含籽粒)和土壤样品,测定水稻地上部生物量、产量及氮素含量,计算水稻地上部氮素吸收量及氮肥利用率,测定土壤供氮能力和有效磷钾含量。【结果】与F100处理相比,GF80处理显著增加早稻产量,6年平均增产707.80 kg/hm2,平均增产率为10.12%,对晚稻产量无显著影响;GF60和GF40处理早稻和晚稻均不减产;GF40、GF60和GF80处理早稻成熟期稻谷生物量无显著变化,晚稻稻谷生物量分别增加7.76%、8.62%和9.48%。GF40、GF60和GF80处理的早稻和晚稻氮肥利用率增加了21.37%~57.16%;GF40处理早稻氮肥农学效率(NAE)增加了99.77%,GF40、GF60和GF80处理晚稻氮肥农学效率分别增加了20.61%、22.88%和17.17%;GF40、GF60和GF80处理早稻氮肥偏生产力分别显著增加了140.28%、55.33%和23.09%。与F100处理相比,GF40、GF60处理早稻成熟期稻谷氮吸收量分别降低了21.16%、11.43%,GF80处理稻谷氮吸收量无显著变化;晚稻成熟期GF40、GF60和GF80处理稻谷氮吸收量分别增加18.21%、29.23%和26.19%;GF40、GF60、GF80处理增加早稻季分蘖期、拔节期、抽穗期及晚稻成熟期土壤潜在供氮能力和总供氮能力,增幅分别为21.38%~316.31%和18.50%~250.61%,早稻不同生育期土壤供氮能力与水稻地上部氮素吸收呈极显著正相关。【结论】种植利用紫云英条件下,赣北双季稻区早稻减施化肥20%~60%可增加水稻土壤供氮能力,提高氮肥利用率、农学效率及偏生产力,实现水稻稳产。早稻减施60%化肥提高了晚稻稻谷氮积累量,但降低了早稻稻谷氮积累量。早稻减施化肥20%可增加早稻产量,对早稻稻谷氮素吸收量无明显影响,但增加了晚稻稻谷氮素吸收。

【Objectives】Chinese milk vetch(CMV)and rice rotation is an efficient practice to take use of fallow paddy field during winter season,and maintain the productivity of paddy field.We studied the potential of fertilizer reduction on rice yield and N efficiency and the soil N supply capacity under the rice-rice-CMV rotation system.【Methods】The field experiment under rice-rice-CMV rotation was established in Gao’an,Jiangxi Province in 2016.The treatments included no fertilizer control(CK),conventional fertilizer rate without returning CMV(F100),and returning CMV combined with conventional chemical fertilizer rate of 100%,80%,60%,and 40%(GF100,GF80,GF60 and GF40)for early rice,and the following late rice was applied with conventional fertilizer rate in all the treatment plots.Plant(including grains)and soil samples were collected at the tillering,jointing,booting,and maturity stages of early rice and at maturity stage of late rice to measure the aboveground biomass,yield,and nitrogen content of rice.The N uptake and utilization efficiency of rice aboveground were calculated,and the N supply capacity and available phosphorus and potassium content of soil were measured.【Results】Compared with F100 treatment,GF80 significantly increased early rice yield by 707.8 kg/hm2,or by 10.12%on average of six years,and did not impact the late rice yield;GF40 and GF60 didn’t significantly affect the early and late rice yield.GF40,GF60 and GF80 treatments didn’t significantly affect grain biomass at maturity stage of early rice while significantly increased grain biomass by 7.76%,8.62%,and 9.48%of late rice at maturity stage,respectively.GF40,GF60 and GF80 treatments significantly increased N use efficiency of early and late rice by 21.37%−57.16%.Simultaneously,GF40 treatment increased N agronomic efficiency(NAE)of early rice by 99.77%,and GF40,GF60 and GF80 treatments increased NAE of late rice by 20.61%,22.88%and 17.17%,respectively.Furthermore,GF40,GF60 and GF80 treatments increased N partial factor productivity of early rice by 140.28%,55.33%,and 23.09%.GF40 and GF60 treatments decreased grain nitrogen uptake by 21.16%and 11.43%,while GF80 treatment did not cause grain N decrease of early rice.GF40,GF60,and GF80 treatments significantly increased grain N uptake of late rice by 18.21%,29.23%and 26.19%,respectively.GF40,GF60,and GF80 treatments significantly increased potential and total soil nitrogen supply capacity by 21.38%−316.31%and 18.50%−250.61%at the tillering stage,jointing stage,and booting stage of the early rice and maturity stage of late rice.【Conclusions】Under rice-rice-Chinese milk vetch rotation system,reducing chemical fertilizer 20%–60%only in early rice could significantly increase soil nitrogen supply capacity during the early and late rice growth period,and significantly improve the N use efficiency,N agronomic efficiency and partial productivity,and sustained rice yield.Reducing chemical fertilizer 20%for early rice could significantly increase grain yield,maintained nitrogen uptake of early rice,and enhanced grain nitrogen uptake of late rice.