玉米土壤有机氮组分的生长季动态变化及其对当季和长期秸秆还田的响应

Variation of soil organic nitrogen fractions in maize field during growing season and its response to current year and long-term straw returning

阐明土壤有机氮组分的生长季变化特征及其对当季和长期秸秆还田的响应有助于合理调控土壤有机氮库,提高土壤肥力。本试验依托辽宁沈阳农田生态系统国家野外科学观测研究站进行田间微区试验,设置单施氮肥和秸秆还田配施氮肥两个处理,分别在播种前、拔节期、吐丝期、灌浆期和成熟期采集土样,采用Bremner法对土壤有机氮组分进行分级。结果表明:在玉米生长季中,土壤各形态有机氮组分呈现明显的动态变化规律。酸解氨态氮含量呈先升高后降低趋势,表明其在土壤氮素转化过程中可能充当临时库的作用;氨基酸态氮在整个生长季内变化不显著;氨基糖态氮在作物生育后期显著低于生育前期;酸解未知态氮在整个生育期内先升高后降低,活性较高;与单施氮肥处理相比,秸秆还田在生长季末期和长期均提高土壤总氮和各酸解态氮组分的含量,并使土壤酸解态氮占土壤总氮比例升高,使未酸解态氮占土壤总氮的比例降低,在当季和长期分别降低了7.2%和3.8%,说明秸秆还田既能提高土壤氮素的有效性,又能够提高土壤的保氮供氮能力。

The analysis of the variation of soil organic nitrogen fractions in growing season and its response to current year and long-term straw returning could provide scientific basis for reasonable regulation of soil organic nitrogen pool and the improvement of soil fertility.A field plot experiment with two treatments was conducted at the National Field Observation and Research Station of Shenyang Agroecosystems,i.e.,single application of nitrogen fertilizer and straw returning combined with nitrogen fertilizer.Soil samples were collected at before-seeding,jointing,silking,filling,and maturity stages.Bremner method was used to classify soil organic nitrogen fractions.The results showed that each of the organic nitrogen fractions in the soil showed obvious dynamic patterns in the whole growing season of maize.Hydrolyzable ammonium content increased firstly and then decreased,indicating that it may act as a temporary pool during soil nitrogen transformation.Amino acid nitrogen did not vary significantly across the growing season.Amino sugar nitrogen was significantly lower in the late growing season than that in the early growing season.Hydrolyzable unknown nitrogen increased and then decreased with high activity across the growing season.Compared with single nitrogen treatment,straw returning increased the contents of soil total nitrogen and hydrolyzed nitrogen at the end of the growing season and in the long term,increased the proportion of hydrolyzed nitrogen to total nitrogen,and decreased the proportion of no hydrolyzed nitrogen to total nitrogen by 7.2% and 3.8% in the current season and long term,respectively.The results indicated that straw returning could not only improve soil nitrogen availability,but also improve the capability of soil nitrogen storage and supply.