地膜覆盖下半干旱区玉米地土壤氮素转化及酶活性响应机制

With the rapid increase in the application area, film fully-mulched ridge–furrow (FMRF) cropping have made great contribution to improve hydrothermal conditions, accelerate nitrogen transformation and increase nitrogen use efficiency, enhance the productivity of farmland, increase farmers income and promote regional ecological restoration. But the effect of plastic mulch on soil nitrogen transformation process, such as mineralization, nitrification, denitrification and immobilization of microorganism and the balance among them, and related enzyme activity change characteristics have not studied yet. This project will take the field-grown maize as research object using 15N isotopic pool dilution, in order to ascertain the change feature of soil nitrogen gross transformation rate, reveal the variation of soil enzyme activity during maize different growth periods and change law of enzyme activity under plastic mulch treatment, illustrate the responding mechanism of soil enzyme activity to nitrogen transformation under plastic mulch treatment. The results obtained from this project will help us to better understand the supplying ability of soil nitrogen and the progress of nitrogen cycling, and will provide theoretical basis for optimizing the field nitrogen management measures and rational application of nitrogen fertilizer.

地膜覆盖沟垄栽培技术在改善旱作地土壤水热条件，加快土壤氮素转化和提高氮素利用效率，提高农田生产力、增加农民收入和促进区域生态恢复方面做出了重要贡献。但对地膜覆盖下土壤水热变化所引起的土壤氮素矿化速率、硝化速率、消耗速率和微生物固定速率等的变化特征，各转化速率之间的平衡关系，以及与之相关酶活性对氮素转化过程的影响还没有进行系统性的研究。因此，本项目拟采用15N同位素稀释法，以半干旱区玉米地为研究对象，明确地膜覆盖下土壤氮素总转化速率的变化特征，揭示玉米不同生育期土壤酶活性的差异以及在地膜覆盖下的变化规律，阐明地膜覆盖下土壤酶活性对氮素转化的响应机制，旨在探明地膜覆盖下土壤的供氮能力和氮素循环过程，为优化田间氮肥管理措施和合理施用氮肥提供理论依据。

旱作农业在我国农业生产中具有十分重要的战略地位，地膜覆盖技术的大面积应用为我国旱作农业的可持续发展做出了重要贡献。氮素是植物生长发育必需的营养元素之一，也是农业生产中最重要的产量限制因子。本项目采用15N同位素稀释法，以半干旱区玉米地为研究对象，明确地膜覆盖下土壤氮素总转化速率的变化特征，揭示玉米不同生育期土壤酶活性的差异以及在地膜覆盖下的变化规律，阐明地膜覆盖下土壤酶活性对氮素转化的响应机制。.主要结论与意义：.（1）地膜覆盖对土壤温度和水分的影响与玉米的生长发育有关。地膜覆盖显著增加玉米生育前期的土壤温度和含水量，玉米生长发育后期增加幅度不明显，而降雨充沛的年份，地膜覆盖能够显著改善整个玉米生长期期的土壤含水量。说明地膜覆盖对土壤温度和含水量的影响与其对玉米生长发育后期的遮阴和蒸腾量的增加有关，这也成了增加产量的关键。.（2）地膜覆盖条件下土壤温度和水分的增加，提高了土壤微生物活性，增加了土壤微生物量碳和氮的含量。通过室内培养试验和野外原位培养试验表明，地膜覆盖增加了土壤氮素的净矿化速率、净硝化速率和净铵化速率，从而增加了土壤氮素的净矿化量、净硝化量和净铵化量。说明地膜覆盖加快了土壤有机氮的矿化，提高了氮素的有效性。.（3）地膜覆盖增加了玉米生长发育中期的土壤蛋白酶、脱氨酶、脱氢酶和脲酶的含量。地膜覆盖也增加了土壤氮素总矿化速率、总消化速率、固定速率和消耗速率。说明地膜覆盖下与氮素转化相关酶的增加催化了氮素的矿化速率，从而加快了氮素转化的过程，土壤氮素矿化速率的加快有助于弥补玉米对土壤氮素的吸收利用，从而减少了肥料氮在土壤中的富集，减少了硝态氮的向下淋溶，避免了环境的污染，为优化田间氮肥管理措施和合理施用氮肥提供理论指导。