减施20%化肥下绿肥翻压量对江西双季稻产量及氮素利用的影响

Effects of green manure on yield and nitrogen utilization of double rice under reduced 20% chemical fertilizer input in Jiangxi Province

【目的】种植绿肥是实现化肥减施的重要措施,研究稻田系统中不同绿肥翻压量对土壤供氮及主作物水稻吸氮规律的影响,以期为江西双季稻区合理利用紫云英,提高水稻产量提供理论依据。【方法】田间试验位于江西双季稻区。在早稻氮磷钾肥用量减施20%条件下,设置冬种并翻压紫云英鲜草15000(G_(1)F_(80))、22500(G_(1.5)F_(80))、30000(G_(2)F_(80))、37500(G_(2.5)F_(80))kg/hm^(2),以及冬闲且水稻不施化肥对照(CK)、冬种紫云英水稻不施化肥(GM)和冬闲常规施肥(F_(100))共7个处理。分析了水稻产量、植株吸氮量、氮肥利用率,以及水稻生育期土壤无机氮含量,并分析了土壤性状和水稻产量、植株吸氮量之间的关系。【结果】与F_(100)相比,G_(1)F_(80)处理早稻产量显著增加11.64%;G_(2)F_(80)处理晚稻产量显著增加7.81%;G_(1)F_(80)、G_(1.5)F_(80)和G_(2)F_(80)处理双季稻总产量分别显著增加5.79%、5.38%和7.17%。其余不同紫云英翻压量处理的产量相比F_(100)均未降低。冬种紫云英配施80%化肥可显著提高早稻稻谷吸氮量、早稻当季氮肥利用率和早稻氮肥偏生产力,提高早稻和晚稻收获期土壤全氮和有机质含量,提升土壤肥力水平。早稻孕穗期、早稻收获期和晚稻收获期,G_(2.5)F_(80)处理土壤铵态氮含量均显著高于F_(100)处理,且为各处理中含量最高。从早稻孕穗期到早稻收获期,不同紫云英翻压量处理氮素累积速率均为正值,水稻植株吸氮量增加,而冬闲常规施肥处理氮素累积速率为负值,水稻吸氮量降低。在水稻生育期,紫云英翻压量小于22500 kg/hm^(2)时,水稻植株吸氮量随翻压量增加而增加,而翻压量大于22500 kg/hm^(2)时,水稻植株吸氮量明显降低。土壤速效钾含量对水稻产量和吸氮量的贡献率最大,对早稻产量和早稻吸氮量的贡献率分别为35.17%和40.16%,对晚稻产量和吸氮量的贡献率分别为21.22%和25.22%,对双季稻产量和吸氮量的贡献率分别为34.83%和27.86%。【结论】在减施常规量20%化肥条件下,种植翻压适量紫云英可提高早稻稻谷吸氮量,促进水稻增产。翻压高量紫云英有利于培育土壤碳库和氮库,提高土壤供氮能力。综合各项分析,在江西双季稻区紫云英翻压量为30000 kg/hm^(2)时效果最好。

【Objectives】Utilizing green manure is an important method for reducing chemical fertilizer application.In green manure-rice cropping system,the characteristics of soil nitrogen(N)supply and rice crop N uptake are still unclear.【Methods】The field experiment was conducted in Jiangxi double-cropping rice area.Under the condition that the amount of N,P and K fertilizers for early rice was reduced by 20%,we set up winter planting with fresh milk vetch incorporation at 15000(G_(1)F_(80)),22500(G_(1.5)F_(80)),30000(G_(2)F_(80)),and 37500(G_(2.5)F_(80))kg/hm^(2),as well as winter fallow and rice with no chemical fertilization as control(CK),winter milk vetch and rice with no chemical fertilization(GM),and winter fallow with conventional fertilization(F_(100)).Rice yield,plant N uptake,N fertilizer use efficiency,and soil inorganic N content during rice growing stages were assessed,while the relationships between soil properties,rice yield,and plant N uptake were analyzed.【Results】Compared with F_(100),G_(1)F_(80) treatment significantly increased the yield of early rice by 11.64%;G_(2)F_(80) treatment significantly increased the yield of late rice by 7.81%;G_(1)F_(80),G_(1.5)F_(80) and G_(2)F_(80) treatments significantly increased the total yield of double rice by 5.79%,5.38%and 7.17%.Compared with F_(100),other treatments with different incorporation amounts of milk vetch did not reduce the rice yield.Utilization of milk vetch combined with 80%chemical fertilizer significantly increased the N uptake of early rice,the N fertilizer use efficiency of early rice and the partial factor productivity of early rice,and increased soil total N and organic matter at the harvest stages of early rice and late rice.In the booting stage of early rice,harvest stage of early rice and harvest stage of late rice,the soil ammonium N content of G_(2.5)F_(80) treatment was significantly higher than that of F_(100),and was the highest among all treatments.From the booting to harvest stage of early rice,the N accumulation rate of each green manuring treatments was positive,indicating that the N uptake of rice plants increased.However,the N accumulation rate of F_(100) was negative,indicating that the N uptake of rice decreased.During the growth period of rice,when the incorporation amount of milk vetch was less than 22500 kg/hm^(2),the N uptake of rice plants increased with the increase of incorporation amount,and the amount of N uptake was significantly reduced when the incorporation amount was greater than 22500 kg/hm^(2).Soil available potassium content had the largest contribution rate to rice yield and N uptake.The contribution rate of soil available K to early rice yield and N uptake by early rice was 35.17%and 40.16%,and to late rice yield and N uptake was 21.22%and 25.22%,and to double-cropping rice yield and N uptake was 34.83%and 27.86%,respectively.【Conclusions】Under the condition of 20%reduction of fertilizer,planting and incorporating appropriate amount of milk vetch can improve the N uptake of early rice and increase rice yield.Incorporating a high amount of milk vetch is beneficial to soil carbon and N pools and improve soil N supply capacity.Based on various analyses,incorporation of milk vetch at 30000 kg/hm^(2) in the double rice area of Jiangxi Province was the best.