施氮量对农田土壤有机氮组分及酶活性的影响

【目的】探讨不同施氮量条件下土壤氮素转化酶活性和有机氮组分含量的变化规律,并分析氮素转化酶活性与各有机氮组分之间的关系,为陇中黄土高原旱作农业区合理制定施肥量和施肥方案提供参考依据。【方法】基于设置在陇中黄土高原定西市李家堡镇麻子川村的不同施氮量（0（CK）、52.5（N1）、105（N2）、157.5（N3）、210（N4）kg N·hm^-2）春小麦长期定位试验,收获后使用Bremner法测定0—40 cm土层中有机氮组分含量,以及4种氮素转化相关酶的活性。【结果】土壤有机氮组分分配比例顺序为氨基酸态氮>酸解铵态氮>酸解未知态氮>氨基糖态氮,同一土层随着施氮量的增加土壤有机碳、全氮、酸解总氮、氨基酸态氮、酸解铵态氮和脲酶活性、蛋白酶活性均呈先增大后降低的趋势,除全氮外其余都在N2处理时最大,全氮含量在N3处理时达到最大;同一处理不同土层间均随土层加深而降低。冗余分析结果表明,全氮含量和蛋白酶活性是影响陇中黄土高原农田有机氮组分分布与转化的关键因子;碳氮比与所有有机氮组分均呈负相关,蛋白酶、有机碳和脲酶与氨基酸态氮呈极显著正相关。【结论】综合而言,N2处理土壤供氮潜力最高,全氮和蛋白酶是影响该区春小麦土壤有机氮组分转化的关键因子。氮肥合理施用能明显提高土壤有机氮含量,不同施氮量条件下土壤有机氮组分变化差异明显,改变了氮素相关转化酶的活性。

Effects of Different Nitrogen Application Rates on Soil Organic Nitrogen Components and Enzyme Activities in Farmland

【Objective】 The changes in enzyme activity conversion and soil organic nitrogen components in different nitrogen application rates were studied, and the relationship between enzyme activity and organic nitrogen component was analyzed. It provided a reference for rationally formulating fertilization amount and fertilization plan in the dry farming area of the Loess Plateau. 【Method】 Based on the different nitrogen (N) application rates (0 (CK), 52.5 (N1), 105 (N2), 157.5 (N3), and 210 (N4) kg N·hm^-2) in Mazichuan village, Lijiabao town, Dingxi city, Loess Plateau, a long-term positioning test was set up on a spring wheat field. Bremner’s method was used to determine the content of organic nitrogen in the 0-40 cm soil layer after harvest, and the activities of four nitrogen-related enzymes were also measured. 【Result】 The order of distribution of soil organic nitrogen components was: amino acid nitrogen>acidolyzable ammonia nitrogen>unknown-acidolyzable nitrogen>amino sugar nitrogen. With the increase of N application rate, soil organic carbon, total nitrogen, total acid nitrogen, amino acid nitrogen, acidolyzable ammonium, urease activity and protease activity increased first and then decreased. Except for total nitrogen, all other components reached the maximum value under N2, and the total nitrogen content reached the maximum value under N3. Different soil layers in the same treatment decreased with the increasing soil depths. The results of redundancy analysis indicated that total nitrogen content and protease activity were the key factors affecting the distribution and transformation of organic nitrogen components in the Loess Plateau of Longzhong. C:N ratio was negatively correlated with all organic nitrogen components, while protease, organic carbon and urease were positively correlated with amino acid nitrogen. 【Conclusion】 In general, N2 treatment had the highest nitrogen supply potential, and the total nitrogen was the key factor affecting the transformation of organic nitrogen components in spring wheat in this area. The changes of soil organic nitrogen composition under different nitrogen application rates were obvious, which changed nitrogen in the conversion enzyme activity.