甜玉米/白三叶草秸秆还田的碳氮矿化研究

豆科/禾本科作物间套作后进行秸秆还田能补充土壤养分,缓解集约化农业生产对环境的压力.根据田间甜玉米/白三叶草套种各作物的秸秆产量,在恒温恒湿条件下进行室内培养,探讨秸秆不同方式还田后土壤微生物量碳、微生物量氮、呼吸产生的CO2和矿化产生的无机氮的变化规律.研究发现,各施肥处理的土壤微生物量碳、微生物量氮均在培养前期出现峰值,后期平稳降低;甜玉米秸秆和白三叶草绿肥同时还田的土壤微生物量碳、微生物量氮在各培养时期均最大,峰值分别达529.57 mg·kg-1和75.50 mg·kg-1,土壤呼吸产生的CO2最多;白三叶草绿肥单独还田有利于土壤无机氮的释放,培养第26 d 无机氮达到最大值,为29.81 mg·kg-1,之后一直在对照处理的1.60倍以上,第80 d达到2.48倍;甜玉米秸秆单独还田不利于土壤无机氮的释放,培养的第26 d至结束,甜玉米秸秆处理的无机氮为对照的13%～53%,最大为7.51 mg·kg-1;甜玉米秸秆配施尿素,短期内不利于土壤无机氮矿化.结果表明,施用有机物料能引起土壤有机质的短期快速转化,甜玉米秸秆和白三叶草绿肥配施有利于维持较大基数的土壤微生物量,单施白三叶草绿肥土壤微生物活性强,最有利于土壤速效氮的释放.

Carbon and nitrogen mineralization of incubated sweet maize

Organic fertilizer derived from intercropped legume and grain crops supplies substantial soil nutrient under intensive cropping system. Microbial biomass carbon and microbial biomass nitrogen, respiration CO₂ and mineralized nitrogen in plant straw fertilized soil were determined under laboratory incubation conditions of constant temperature and moisture based on field aboveground yields of intercropped sweet maize straw and white clover straw. Results show that microbial biomass carbon and microbial biomass nitrogen in fertilized soil peak in the first several days, and then decline. Intercropping Incubating both sweet maize straw and white clover have the highest yield, maxima of 529.57 mg·kg^-1 and 75.50 mg·kg^-1 respectively. They also release the most respired CO₂ the most among all treated soils. The best mineral nitrogen release is in white clover intercroppingincubating, with a maximum of 29.81 mg·kg^-1 under a 26-day culture, and then keeping 1.60 times the control and reaching 2.48 times at 80-day culture. Sweet maize incubatingintercropping has the least mineral nitrogen release. It is 13%~53% of the control under a 26-day culture, with a maximum of 7.51 mg·kg^-1. Soil nitrogen mineralizatiomineralization is insignificant under sweet maize incubatingintercropping with urea in short-term. It is concluded that plant straw intercropping fertilizing enhances soil organic matter turnover. Intercropping Incubating of sweet maize and white clover may induce significant higher soil microbial biomass. White clover incubating intercropping activates soil microbe which is beneficial to soil nitrogen mineralization.