小麦生长季土壤不同形态氮素的含量及淋失特征

Different Forms of Nitrogen Contents and Distribution Characteristics of Soil at Wheat Growth Season

为了探索不同形态的氮素在农田冬小麦土壤中的含量和分布特征，选择在江苏省张家港市冬小麦农田土壤中分4个小区进行剖面试验。结果表明：田间表层土壤中氨氮含量施肥前后变化量为5．7mg／kg，变化幅度不大，氨氮在土壤中垂向分布较均匀。氨氮在小麦生长季的变化平稳，施肥和降雨对氨氮在土壤中的垂向迁移影响较小，与氨氮自身带正电性质和土壤特性有关，不同施肥处理之间变化趋势相同，差异不明显。硝氮含量主要受施肥量、降雨时机和降雨强度的影响，施肥后其含量显著增加，施肥后第4d硝氮含量达到最大值，比施肥前高出42倍。88．4％的硝氮集中分布在深度为O～30cm的土壤中。不同施肥处理之间的差异主要体现在0～50cm深度土壤中。硝氮在土壤中随降雨垂向迁移较快，施肥后20d内淋失严重，对地下水有一定影响。施肥管理时，一次施用大量氮肥对促进小麦生长的效果不佳，在小麦生长的关键时期分多次合理施用能显著提高氮肥的利用率。

In order to investigate the contents and distribution characteristics of the different forms of nitrogen m the winter eornnela soil located in Zhangiiagang city, 3iangsu province, four sub-regions are chosen within the field to conduct profile experiment re- search. The results show that the contents of ammonia nitrogen in the field have small variation of 5.7 mg/kg before and after fertili- zation, slightly changed and the ammonia nitrogen in the soil vertical distribution is relatively uniforrra Ammonia nitrogen in the wheat growing season changes smoothly. Also, fertilization and rainfall have little effect on the ammonia nitrogen vertical migration in the soil because of the positively charged properties of ammonia nitrogen and soil characteristic. The trend of the change is the same and the gaps are little among different fertilizer treatments. The nitrate nitrogen contents in the farmland soil are highly affect- ed by the fertilizing amount, rainfall time and rainfall intensity. The contents will remarkably increase after the fertilizer application and reaches maximum value, which is 42 times higher than the contents value before fertilization at the fourth day. 88.4% of the ni- trate nitrogen mainly distributed in the depth of 0~30 cm soil. The diversity of different fertilizer treatments mainly reflects in the depth of 0~50 cm soil. Nitrate nitrogen leaching is very serious in 20 days after fertilizing and has a certain influence on the ground water. The effect is not the best if the large amount of nitrogen fertilizer is used in one time application to promote the wheat growth, so it will be an useful method that reasonable application of several times in the key period of wheat growth to improve the utilization rate of nitrogen fertilizer.