有机无机氮肥比例对稻田土壤肥力和作物产量的短期效应

Short-term effects of organic to chemical nitrogen proportion on paddy soil fertility and double rice yield

【目的】研究短期内(<5年)有机无机氮配施比例对土壤肥力以及水稻产量的影响,以明确提升地力与兼顾产量的养分管理措施。【方法】田间定位试验于2017—2021年在长江中下游的红壤双季稻田进行。共设6个处理:不施肥(CK),单施化肥(CF),有机氮比例分别为25%、50%、75%与100%的有机无机肥配施处理(25%ON,50%ON,75%ON,100%ON)。2021年,早、晚稻成熟后测产;晚稻收获后采集耕层土壤样品,分析土壤物理性状(容重与大团聚体含量)、化学性状(pH、有机质、全氮、全磷、全钾、有效氮、有效磷、速效钾、有效锌、有效硅)与生物学性状(脲酶、酸性磷酸酶、β-葡糖苷酶、微生物生物量碳、微生物生物量氮),采用土壤肥力综合指数(IFI)评价不同比例有机肥料的培肥效果,运用偏最小二乘路径模型(PLS-PM)分析有机无机肥配合比例对IFI以及产量的影响。【结果】随着有机肥比例的提高,有机无机肥配施提升土壤物理、化学、生物学性状的效果也随之提升。土壤有机质含量和β-葡糖苷酶活性与其它所有指标的相关关系均达显著水平,有机碳含量与碳循环过程对土壤物理结构、养分以及微生物活性均有较强影响。相对于其他指标,土壤全磷与有效磷的变异系数较大,受有机肥投入的影响较大。施肥显著提高了土壤IFI,有机无机肥配施的肥力指数显著高于单施化肥,且随着有机肥配施比例升高而递增,而双季稻产量则随着有机肥配施比例升高而递减,有机肥配施比例≤50%时,产量与单施化肥持平,>50%时表现为减产。PLS-PM分析结果显示,有机肥和无机肥投入对IFI均有显著影响,有机肥的效应大于无机肥;有机肥对产量无显著影响,而无机肥投入量对产量影响显著。【结论】有机无机肥配施可以全面改善土壤环境,提高土壤肥力,且有机肥配施比例越高效果越好。但如果培肥时间较短(5年以内),化肥氮对产量的贡献占绝对优势,有机氮的投入比例应控制在50%以下,才能兼顾地力提升与产量的维持。

【Objectives】We explored the effects of organic fertilizer proportions in total N input on the rice yield and soil fertility in short-term,in order to propose a reasonable organic fertilizer ratio for improving soil fertility and rice yield simultaneously.【Methods】A localized field experiment was conducted successively for five years from 2017 to 2021 under double rice systems in Yichun City,Jiangxi Province.The experimental scheme was composed of no fertilizer control(CK),sole chemical NPK fertilizers(CF),organic N(pig manure)replacing 25%,50%,75%and 100%of chemical N input(denoted as 25%ON,50%ON,75%ON,and 100%ON),all the fertilizer treatments had the same total N,P and K input.The grain yields of early and late rice were recorded every year at harvest.At harvesting of late rice in 2021,tillage layer soil samples were collected for the determination of 15 physical,chemical properties,and biological properties indicators.The soil integrated fertility index(IFI)of treatment was calculated and the importance of organic and chemical fertilizer on IFI and yield was assessed by partial least squares path model(PLS-PM).【Results】Compared to CF treatment,organic fertilizer promoted the soil physical,chemical and biological properties,and the effect was enhanced with the increasing of organic N proportion.Soil organic matter andβ-glucosidase activity were significantly correlated with the soil chemical and physical indicators.Among the tested indicators,total and available P content had the highest variable coefficient values,showing their sensitivities to the input of organic fertilizer.All the fertilization treatments improved the IFIs,and the four organic replacement treatments did better than CF treatment.The IFIs increased with the enhancing of organic N proportion,while the grain yield effect was on the contrary.The 25%ON and 50%ON treatment were recorded similar annual yield with CF,while 75%ON and 100%ON treatments were reordered significantly lower annual yield.PLS-PM results showed that both chemical and organic fertilizers had significant effect on the IFIs,and the effect of organic fertilizer was higher than that of chemical fertilizer;organic fertilizer had no significant effect on rice yield,while inorganic fertilizer had significant effect.【Conclusions】Chemical fertilizer plays a decisive role for maintenance of rice yield,but limited effect on soil fertility.Whereas organic fertilizer shows no obvious effect on rice yield in short term,but contributes greatly to the improvement of soil fertility.The proportion of organic fertilizer nitrogen should be controlled within 50%for maintaining high rice yield and improving soil fertility simultaneously.