土壤有机碳对肥料氮向土壤有机氮库转化的调控机制

Transformations of fertilizer nitrogen into different soil organic nitrogen pool are regulated by soil organic carbon. It will be a critical path to achieving high nitrogen use efficiency, ensuring high yield of grain and agricultural sustainable development in the black soil region of northeast China. However, the mechanisms of soil organic carbon regulation on fertilizer nitrogen transformation in soil organic nitrogen pool remain largely unknown. To probe into the important scientific issue, based on the long-term field experiment, micro-plot experiment will be established in northeast China. The spring maize cultivar widely grown by the local farmers was used as experiment material. Using 15N tracing combined with soil particle size fractions technique, through micro-plot experiment associated with laboratory simulation, different organic fertilizers change soil C/N value and regulate fertilizer nitrogen transformation in soil organic nitrogen pool are used as the breakthrough point of the present study. The project will be intended to elucidate effect of soil organic carbon regulation on the transformation dynamics of fertilizer nitrogen into soil organic nitrogen pool, the migration characteristics and the stabilize mechanism of residue fertilizer nitrogen in different soil particle size fractions of soil organic nitrogen pool, the mineralization characteristics of residue fertilizer nitrogen in different soil particle size fractions of soil organic nitrogen pool, disclosing the mechanisms of soil organic carbon regulation on fertilizer nitrogen transformation in soil organic nitrogen pool. The results will provide theoretical basis for achieving high nitrogen use efficiency in black soil region in northeast China.

土壤有机碳调控肥料氮向土壤有机氮库的有效转化，是实现东北黑土区氮素养分高效利用的关键途径，是保障东北黑土区粮食高产和农业可持续发展的战略需要。针对东北黑土区土壤有机碳对肥料氮向土壤有机氮库转化的调控机制不清的科学瓶颈，以春玉米种植体系为研究对象，采用15N同位素示踪结合土壤颗粒分级等现代分析技术，利用田间连续定位试验平台结合室内模拟，以不同有机培肥方式调节土壤C/N比进而调控肥料氮向土壤有机氮库转化为切入点，明晰土壤有机碳对肥料氮向土壤有机氮库转化的动力学规律、稳定机理和矿化调控机制为主线，重点研究土壤有机碳调控下肥料氮向土壤有机氮库转化的动力学特征，土壤有机碳调控下残留肥料氮在土壤不同粒级有机氮库的迁移及稳定，土壤有机碳调控下残留肥料氮在土壤不同粒级氨基酸态氮库的矿化特征，揭示土壤有机碳对肥料氮向土壤有机氮库转化的调控机制，为实现我国典型黑土区氮素养分高效利用的有效调控提供依据。

对东北春玉米生产上存在的氮肥利用率低、秸秆资源丰富但有效还田率低等问题，利用15N 示踪技术，通过田间连续定位试验结合室内培养，研究单施化肥（N1）、N1+50%玉米秸秆（N2）、N1+100%玉米秸秆（N3）、N1+相当于50%玉米秸秆的玉米秸秆炭（N4）、N1+相当于100%玉米秸秆的玉米秸秆炭（N5）处理下对肥料氮向土壤有机氮库转化的动力学规律、稳定机理和矿化调控机制的影响，为实现我国典型黑土区秸秆有效还田和肥料氮素养分高效利用提供一定的理论依据。主要得出以下结论：. （1）玉米全生育期内，各处理下土壤氨基酸态氮呈现先平稳后升高的趋势，15N-氨基酸态氮呈现先下降后升高的趋势；酸解铵态氮变化趋势较为平缓，在灌浆期略有下降，15N-酸解铵态氮含量在整个生育期内逐渐下降。秸秆、秸秆炭还田下土壤氨基酸氮库中含量较高的氨基酸由高到低依次为：亮氨酸>异亮氨酸≥苯丙氨酸>缬氨酸>丙氨酸，且土壤15N-氨基酸氮库中15N-亮氨酸、15N-甲硫氨酸、15N-丙氨酸原子百分超（APE）最高。与 N1相比，N3处理能促进外源肥料氮向土壤氨基酸态氮库中的丙氨酸、缬氨酸、异亮氨酸和苯丙氨酸转化。. （2）秸秆、秸秆炭还田显著提高粉粒、粘粒中总氮分布强度，显著提高肥料氮在土壤各粒级中的分布强度，使缬氨酸、亮氨酸、异亮氨酸、苯丙氨酸从砂粒向粉粒中转移。. （3）芳香度变化趋势由高到低为N5>N4>N3>N1>N2，疏水碳含量/亲水碳含量比值由高到低依次为 N5>N4>N3>N2>N1。N5处理下土壤碳库稳定性高于其他处理。. （4）秸秆、秸秆炭还田处理可显著提高土壤综合肥力（P<0.05）；与N1相比，N2、N3处理土壤有机氮的矿化量和矿化率分别显著提高了23.40%和22.90%，53.00%和35.80%（P<0.05），N2、N3、N4和N5处理下外源肥料15N的矿化量和矿化率分别显著提高了66.50%和50.00%，213.30%和278.99%，39.40%和36.30%，92.00%和40.00%（P<0.05）。. 秸秆、秸秆炭还田可提高东北黑土土壤肥力、农学效益及土壤潜在矿化势，促进外源肥料氮向土壤氨基酸态氮中的转化。