施氮量对半湿润区小麦-玉米轮作系统土壤氮的影响

为探讨不同施氮量对黄土高原半湿润地区冬小麦-夏玉米轮作系统土壤氮动态变化的影响,2016-2018年采用田间试验,研究了不同氮肥用量下冬小麦-夏玉米轮作系统作物不同生育时期0～200 cm土层土壤氮的动态变化。结果表明,不同氮肥处理间0～60 cm土层土壤全氮储量差异显著,两年试验后较试验前,施氮0 kg·hm~(-2)(N_0)、100 kg·hm~(-2)(N_(100))、200 kg·hm~(-2)(N_(200))、300 kg·hm~(-2)(N_(300))和400kg·hm~(-2)(N_(400))处理的土壤全氮增量分别为-180、-245、288、627和709 kg·hm~(-2)。不同氮肥处理间0～200 cm土层土壤硝态氮含量及其储量差异显著,土壤铵态氮含量无显著性差异。两年试验后较试验前,N_0和N_(100)处理0～200 cm土层土壤硝态氮储量明显降低,N_(200)处理变化不显著,3者均无明显硝态氮下移,而N_(300)和N_(400)处理0～200 cm土层土壤硝态氮储量显著增加,向深层土壤(100～200 cm)下移明显。每季作物施氮200 kg·hm~(-2)可以减少深层土壤硝酸盐累积量。

Effect of Nitrogen Application on Dynamic Changes of Soil Mineral Nitrogen in Wheat-Maize Rotation System in the Semi-Humid Region

In order to study the effect of nitrogen application on the dynamic change of soil nitrogen in the wheat-maize rotation system in the semi-humid region of the Loess Plateau,the dynamic changes of soil mineral nitrogen in 0-200 cm soil layer during different growth stages of wheat and maize were compared and analyzed. The result show that after two-year experiment,compared with the soil total nitrogen amount before the experiment,the soil total nitrogen stocks in the 0-60 cm layer was significantly increased with the increase of nitrogen fertilizer application rate,and the increments of 0 kg·hm^-2(N₀),100 kg·hm^-2(N₁₀₀),200 kg·hm^-2(N₂₀₀),300 kg·hm^-2(N₃₀₀) and 400 kg·hm^-2(N₄₀₀) were -293,-245,288,673 and 709 kg·hm^-2,respectively. Nitrogen application significantly increased the content and amount of soil nitrate,while there was no significant effect on the content and amount of soil ammonia. After the two-year experiment,the nitrate amount under N₀ and N₁₀₀ treatments in the 0-200 cm soil layer showed a decreasing trend,without significant nitrate leaching in the soil. N₂₀₀ treatment showed no significant increase of nitrate and no significant nitrate leaching in the soil. However,compared with N₀ treatment,the nitrate amount under N₃₀₀ and N₄₀₀ treatments in soil layer 0-200 cm was increased significantly,and the content of nitrate moved down to deep soil(100-200 cm) significantly. Therefore,200 kg·hm^-2 of nitrogen application can reduce the nitrate accumulation in deep soil.