不同比例有机氮肥替代无机氮肥对双季稻生长和土壤供氮能力的影响

Effects of different proportions of organic nitrogen fertilizer replacing inorganic nitrogen fertilizer on growth and soil nitrogen supply capacity of double cropping rice

通过田间试验,设置不施氮肥(CK)、常规施肥(N100)、有机氮替代25%无机氮肥(N75)以及有机氮替代50%无机氮肥(N50),共4个处理,分析了不同比例有机氮肥替代条件下对双季稻的产量及其构成、氮肥吸收与利用效率以及土壤供氮能力的影响。试验结果表明,不施氮肥水稻可生产籽粒9 971 kg·hm^(-2)(早稻5 457 kg·hm^(-2)和晚稻4 514 kg·hm^(-2)),氮肥增产贡献率为25.6%条件下,施氮肥可显著提高水稻籽粒产量。与常规施肥处理相比,有机替代处理水稻籽粒产量明显提高,尤其是有机替代25%无机氮效果更好。无论是早稻还是晚稻,N75处理水稻有效穗数均是最高的,其次是N50和N100,CK的是最低的。但处理间水稻收获指数、千粒重和穗粒数没有显著差异。有机无机配施也提高了水稻对氮的吸收。与N100相比,N75和N50早稻籽粒和秸秆吸氮量提高了,N75晚稻籽粒和秸秆吸氮量显著提高了25.5%和43.7%。施氮肥引起了氮素在土壤中的累积,尤其是N100处理的,其氮素盈余量远高于施用有机肥处理的(N75和N50)。无论是早稻还是晚稻,N75处理的氮肥表观利用率最高,其次是N50,N100的最低。而施氮处理间氮素内部利用效率和氮肥偏生产力没有显著差异。施氮肥提高了土壤中全氮、微生物量氮、水溶性氮、铵态氮和硝态氮的含量。与N100相比,N75处理土壤全氮、微生物量氮、水溶性氮、铵态氮和硝态氮的含量显著提高了14.0%、42.8%、68.8%、25.1%和107.1%。但N75与N50处理间土壤养分含量却没有显著差异。在常规施氮量的条件下,与单施化肥相比,施氮比例为25%有机肥+75%无机肥的配施方案,能够保证水稻籽粒产量、吸氮量和氮素利用效率不下降的前提下,显著提升土壤供氮能力,因此,从南方稻-稻轮作体系的长期生产来看,有机无机配施比纯化肥处理相比,具有更大的优势和潜力。

Through field experiments,four treatments were set up:no nitrogen fertilizer(CK),conventional fertilization(N100),25%organic nitrogen replacing inorganic nitrogen(N75),and 50%organic nitrogen replacing inorganic nitrogen(N50)to analyze the effects of different proportions of organic nitrogen substitution on the yield and composition of double-cropping rice,nitrogen fertilizer absorption and utilization efficiency,and soil nitrogen supply capacity.The experimental results showed that under the condition of no nitrogen fertilizer,rice could produce a grain yield of 9971 kg hm^(-2)(early rice 5457 kg·hm^(-2) and late rice 4514 kg·hm^(-2)).With a nitrogen fertilizer contribution rate of 25.6%,nitrogen fertilization significantly increased rice grain yield.Compared with conventional fertilization treatment,the organic substitution treatments significantly increased rice grain yield,especially with 25%organic nitrogen substitution showing better results.Whether early rice or late rice,the N75 treatment had the highest effective panicle number,followed by N50 and N100,with CK being the lowest.However,there were no significant differences in rice harvest index,thousand-grain weight,and grains per panicle among the treatments.The combination of organic and inorganic fertilizers also increased nitrogen absorption by rice.Compared with N100,the nitrogen uptake of grains and straw in early rice increased in N75 and N50 treatments,and the nitrogen uptake of grains and straw in late rice under N75 treatment significantly increased by 25.5%and 43.7%,respectively.Nitrogen fertilization caused nitrogen accumulation in the soil,especially in the N100 treatment,with much higher nitrogen surplus than in the organic fertilizer treatments(N75 and N50).Whether early rice or late rice,the apparent nitrogen use efficiency of the N75 treatment was the highest,followed by N50 and N100 being the lowest.There were no significant differences in internal nitrogen use efficiency and nitrogen fertilizer productivity among the nitrogen treatments.Nitrogen fertilization increased the contents of total nitrogen,microbial biomass nitrogen,water-soluble nitrogen,ammonium nitrogen,and nitrate nitrogen in the soil.Compared with N100,the soil contents of total nitrogen,microbial biomass nitrogen,water-soluble nitrogen,ammonium nitrogen,and nitrate nitrogen under the N75 treatment significantly increased by 14.0%,42.8%,68.8%,25.1%and 107.1%,respectively.However,there were no significant differences in soil nutrient contents between the N75 and N50 treatments.Under the condition of conventional nitrogen fertilization,compared with single chemical fertilizer application,the combined application of 25%organic fertilizer+75%inorganic fertilizer can significantly improve soil nitrogen supply capacity without reducing rice grain yield,nitrogen uptake,and nitrogen use efficiency.Therefore,from the perspective of long-term production in the southern rice-rice cropping system,the combined application of organic and inorganic fertilizers has greater advantages and potential compared with pure chemical fertilizer treatment.