秸秆还田与水分管理对双季水稻氮素吸收及氮肥?利用率的影响

秸秆还田是促进农田养分循环的重要方式,也对提升农田地力有较好效果。以南方典型双季稻田为研究对象,设置三个秸秆还田水平和两种水分管理方式的两因子田间定位试验,于定位试验开展后的第5年通过测定早稻和晚稻季稻田土壤无机氮、微生物生物量氮动态、植株吸氮量动态以及收获期主要土壤肥力因子、水稻产量和植株各部分氮素累积量,分析秸秆还田与水分管理制度下水稻氮素吸收和氮肥利用率的特征及其影响因素。结果表明:秸秆还田提高了土壤有机碳和全氮含量以及土壤p H,长期淹水较之间歇灌溉降低了土壤有机碳、全氮和全磷含量。在氮肥用量一致条件下,早稻季秸秆还田降低了分蘖期土壤氮素有效性,导致水稻生育期内氮素吸收量显著下降,且显著降低水稻籽粒产量及氮肥利用率;氮肥利用率较对照下降2.0~7.6个百分点,且随秸秆还田量的增加而降低。晚稻季秸秆还田提高了生育期内土壤氮素有效性,显著提高了水稻生育期内氮素吸收量,增加水稻产量且显著提高氮肥利用率;氮肥利用率较对照提高8.6~13个百分点,且随秸秆还田量的增加而增加。研究表明,间歇灌溉和长期淹水灌溉两种水分管理方式对水稻氮素吸收、籽粒产量及氮肥利用率的影响差异不显著。早稻季秸秆还田配合长期淹水灌溉将加剧水稻产量和氮肥利用率下降。双季稻稻田实行间歇灌溉下的早稻季秸秆不还田、晚稻季秸秆全量还田(6 t/hm2)有利于获得较高水稻产量和氮肥利用率。

The effects of straw incorporation and water management on nitrogen uptake and nitrogen use efficiency in a double rice cropping system

Straw incorporation is an important measure to promote nutrients cycling in farmlands and can also improve farmland productivity. Based on the two main water management regimes in paddy production, that is intermittent irrigation and continuous flooding, the present study investigated the effects of different water management regimes on nitrogen (N) uptake and N use efficiency (NUE) in a double rice cropping system with straw incorporation in the fifth year of a long-term field experiment in Changsha county, Hunan province, China. The study had six treatments: no N fertilizer application and no straw incorporation with intermittent irrigation (CK), N fertilizer application and no straw incorporation with intermittent irrigation, N fertilizer application and low rate straw incorporation with intermittent irrigation, N fertilizer application and high rate straw incorporation with intermittent irrigation, N fertilizer application and no straw incorporation with continuous flooding, and N fertilizer application and no straw incorporation with continuous flooding. Dynamics of soil inorganic N contents, soil microbial biomass N (MBN) contents, plant N uptake and rice grain yields and N accumulation in different parts of plants in the harvest stage were measured in both early and late rice seasons in the fifth year of the field experiment. Major soil fertility properties were also measured after the late rice harvest. The results showed that straw incorporation increased soil organic carbon (SOC) and total N (TSN) as well as soil pH as compared with no straw incorporation, while continuous flooding reduced SOC, TSN and soil total phosphorus as compared intermittent irrigation. Under the same N fertilizer application rate, straw incorporation in the early rice season decreased soil inorganic N content and soil MBN content in the tillering stage, and also significantly decreased rice N uptake, grain yield as well as NUE; the NUE in the straw treatments decreased by 2.0% to 7.6% as compared with CK, and decreased with the increase of straw incorporation rate. Straw incorporation in the late rice season increased soil inorganic N content and soil MBN content in the whole crop season, and significantly increased rice N uptake, grain yield as well as NUE; the NUE in the straw treatments increased by 8.6% to 13% as compared with CK, and increased with the increase of straw incorporation rate. The two water management regimes showed no significant influences on rice N uptake, grain yield as well as NUE. Straw incorporation with continuous flooding in the early rice season caused the decrease of rice grain yield and NUE as compared with straw incorporation with intermittent irrigation. Our results indicate that in the double rice cropping system, relatively high yield and high NUE can be achieved with no straw incorporation in the early rice season and straw incorporation at a rate of 6 t/hm2 in the late rice season under the water management regime of intermittent irrigation.