秸秆还田与氮肥运筹对土壤水碳氮耦合及作物产量的影响

探究全覆膜双垄沟播栽培下玉米秸秆还田与氮肥运筹对土壤水、碳、氮及作物产量的影响,为内蒙古黄土高原秸秆还田氮肥合理施用和节氮、高效秸秆还田技术研发提供科学依据。对比分析了氮肥习惯施用(FN)、氮肥习惯施用配合秸秆还田(FNS)、氮肥高量施用配合秸秆还田(HNS)、氮肥后肥前移施用(RN)、氮肥后肥前移施用配合秸秆还田(RNS)5种不同耕作措施对玉米农田土壤水分、土壤碳氮、酶活性、微生物量及玉米籽粒产量的影响,并通过相关分析和通径分析进一步揭示土壤理化性质和生物学性质变化规律及其耦合效应,明确秸秆还田玉米田不同氮肥运筹方式下土壤水碳氮演变特征。结果表明,与不还田相比,秸秆还田可显著提高0～100 cm土层土壤水分含量,且玉米秸秆还田与全膜垄沟栽培结合后(FNS、HNS、RNS),二者的协同效应较单一地膜覆盖(FN、RN)增强了土壤纳雨增墒能力,为秸秆的正常腐解提供了适宜水热环境；秸秆还田下不同氮肥运筹处理较对照FN均可显著提高土壤有机质和全氮含量,其中以氮肥后肥前移施用配合秸秆还田和氮肥高量施用配合秸秆还田提升效果最显著,土壤过氧化氢酶、脲酶、蔗糖酶和碱性磷酸酶活性以及微生物量碳、氮明显增加,表现为0～20 cm土层大于20～40 cm土层,秸秆不还田氮肥习惯施用和氮肥后肥前移施用无显著性差异；土壤微生物量碳、氮与土壤酶活性和土壤碳氮呈显著或极显著正相关关系,且土壤微生物量碳、氮对土壤有机质、蔗糖酶、全氮和过氧化氢酶变化较敏感,对土壤性质变化具有一定指示作用。在产量方面,还田处理FNS、HNS、RNS较对照FN分别提高5.30%、10.93%、11.41%,且氮肥的常量投入即可获得较高的氮肥偏生产力。综合土壤因子、玉米产量和氮素利用率来看,秸秆还田条件下可通过调整氮肥的后肥前移平衡土壤碳氮收支,实现节本增产增效,同时提高氮肥利用率,是内蒙古黄土高原地区一种节氮、稳产、增效秸秆还田技术模式。

Effects of Straw Returning and Nitrogen Application on Soil Water, Carbon and Nitrogen Coupling and Crop Yield

To explore the effects of corn straw returning and nitrogen fertilizer application on soil water, carbon, nitrogen and crop yield under full film mulching and double ridge furrow sowing, in order to provide scientific basis for the research and development of rational application of nitrogen fertilizer and high efficiency and saving nitrogen straw returning technology in the Loess Plateau of Inner Mongolia. The effects of five different tillage measures on soil moisture, soil carbon and nitrogen, enzyme activity, microbial biomass and grain yield of maize were compared and analyzed with five different tillage measures: nitrogen used to apply (FN), habitual application of nitrogen combined with straw returning (FNS) , high application of nitrogen combined with straw returning(HNS) , nitrogen reducing topdressing proportion to basal(RN), nitrogen reducing topdressing proportion to basal combined with straw returning (RNS). And through correlation analysis and path analysis to further reveal the changes of soil physical and chemical properties and biological properties and their coupling effects, and clarify the evolution characteristics of soil water, carbon and nitrogen under different nitrogen fertilizer application methods of straw returning to corn field. Compared with not returning straw to field, straw returning could significantly increase the soil water content of 0~100 cm soil layer, and the synergistic effect of corn straw returning and full film ridge cultivation (FNS, HNS, RNS),) was stronger than that of single plastic film mulching (FN, RN), which provided a suitable hydrothermal environment for the normal decomposition of straw. Different nitrogen fertilizer treatments under straw returning could significantly increase the content of soil organic matter and total nitrogen compared with the control FN, among which the forward application of nitrogen fertilizer combined with straw returning and high amount of nitrogen fertilizer combined with straw returning had the most significant effect, The activities of catalase, urease, sucrase and alkaline phosphatase as well as microbial biomass carbon and nitrogen in soil increased significantly, and the activity of catalase, urease, sucrase and alkaline phosphatase in 0~20 cm soil was higher than that in 20~40 cm soil, There was no significant difference between the habitual application of nitrogen fertilizer without straw returning and the forward application of nitrogen fertilizer. Soil microbial biomass carbon and nitrogen were significantly or very significantly positively correlated with soil enzyme activity and soil carbon and nitrogen, and soil microbial biomass carbon and nitrogen were sensitive to the changes of soil organic matter, sucrase, total nitrogen and catalase. It can indicate the change of soil properties. In terms of yield, the yield of FNS, HNS and RNS increased by 5.30%, 10.93% and 11.41% respectively compared with the control FN, and the higher partial productivity of nitrogen fertilizer could be obtained with the constant input of nitrogen fertilizer. According to the comprehensive soil factors, corn yield and nitrogen use efficiency, under the condition of straw returning to the field, the soil carbon and nitrogen budget can be balanced by adjusting the forward movement of nitrogen fertilizer, so as to save cost, increase production and increase efficiency, and improve nitrogen use efficiency at the same time. It is a technical model of saving nitrogen, stable yield and increasing efficiency of straw returning to the field in the Loess Plateau of Inner Mongolia.