局部根区滴灌与穴施尿素对土壤氮素空间分布的影响

为研究节水灌溉条件下穴施尿素、滴灌施肥对土壤铵态氮、硝态氮和碱解氮运移的影响,2019年在甘肃农业大学遮雨棚内开展施肥与灌溉试验,采用穴施尿素和滴灌施肥两种施肥方式,施纯氮量240 kg·hm^-2和180 kg·hm^-2,充分灌溉量和局部根区滴灌量分别是14 L和7 L。测定在距离滴头水平30 cm、垂直40 cm范围内土壤铵态氮、硝态氮和碱解氮含量,分析施肥与灌溉后土壤氮素转化及迁移特征。结果表明,土壤硝态氮更容易随灌水发生水平迁移,而土壤铵态氮更容易向土壤纵深迁移。土壤氮素含量的空间变异大小依次为:硝态氮>铵态氮>碱解氮;土壤硝态氮、铵态氮和碱解氮含量的平均变幅分别为32%～40%、26%～37%和6%～12%。局部根区滴灌土壤硝态氮含量的空间变幅比充分灌溉减小16%～20%。穴施尿素土壤铵态氮含量的空间变幅比滴灌施肥减小12%～28%。穴施尿素和局部根区滴灌调控土壤氮素转化速率,赋予肥料养分缓释性能,从而提高土壤氮素供应能力。因此,穴施尿素结合局部根区滴灌是较优的施肥与灌溉方式。

Effects of partial root|zone irrigation and fertilization on spatial distribution of available nitrogen in soil

In order to study the effects of irrigation and fertilization in root zone on the transformation of soil nitrogen (N), two fertilization methods including hole applying urea and fertigation were used with fertilization rates of 240 kg·hm^-2 and 180 kg·hm^-2. During the experimental time, two irrigation methods including full irrigation and partial root zone irrigation were tested separately, with irrigation amounts of 14 L and 7 L. The NH⁺₄-N, NO^-₃-N, and alkaline N contents in soil were investigated, and the spatial distribution characteristics of different forms of N after fertilization and irrigation were analyzed. The results showed that the NH⁺₄-N content in soil was more easily distributed in the soil, while the NO^-₃-N content in soil was more likely to migrate horizontally. In terms of spatial distribution, the variation of soil N content was: NO^-₃-N > NH⁺₄-N > alkaline N. The spatial variation of soil NO^-₃-N content was 32%~40%, that of NH⁺₄-N content was 26%~37%, and that of alkaline N content was 6%~12%. The spatial variation of NO^-₃-N content in partial root|zone irrigated soil was 16%~20% less than that in full irrigated soil. The spatial variation of NH⁺₄-N content in urea hole|application soil was 12%~28% less than that in drip|fertilized soil. Therefore, N conversion rate in soil can be regulated to maintain the effect of nutrient stability release. The optimal method of fertilization and irrigation was the combination of hole|applying urea and partial root|zone irrigation, which improved the soil N supply capacity in this experiment.