不同施肥时序滴灌双点源交汇下土壤水氮分布研究

【目的】探究不同施肥时序下滴灌双点源交汇水、氮的运移规律和分布特征,为滴灌系统施肥装置的合理运行提供技术支撑。【方法】通过室内土槽试验,设置3个硝态氮质量浓度(300、600、900 mg/L)和3种施肥时序(1/2N-1/2W、1/4W-1/2N-1/4W、3/8W-1/2N-1/8W),分析了土壤湿润锋的运移以及水分、硝态氮在土体内的分布情况。【结果】交汇前湿润锋在水平和垂直方向上的运移距离与时间t符合幂函数关系,在交汇面垂直方向上的湿润锋运移距离与时间t可用二项式拟合。各处理的水分分布规律基本相同,随深度的增加,土壤含水率降低,从0～10 cm的30%～35%缓慢降低至10～15 cm土层的19%～25%。在交汇面上的土壤含水率不大于相同土层其他位置的含水率,但硝态氮量比相同土层其他位置的大。增加肥液质量浓度,土体内相同位置的硝态氮量增加。不同施肥时序下,硝态氮在点源交汇区域的内部和边缘的量存在差异。【结论】综合考虑硝态氮的分布规律和减少淋失,在点源交汇情况下,采用水-肥-水的施肥时序(即1/4W-1/2N-1/4W、3/8W-1/2N-1/8W)较肥-水的施肥时序(1/2N-1/2W)能减少硝态氮在点源交汇区域的边缘积累,控制氮肥的淋失。

Distribution of Soil Water and Fertilizer under Double Points Source of Drip Irrigation in Different Fertilization Sequences

【Objective】Research the transport routine and distribution characteristics of water and fertilizer under the intersection of double points source of drip irrigation within different fertilizer's sequences, furthermore, to provide theoretical guidance for the design and effective operation of drip irrigation system.【Method】By performing indoor soil-bin experiments, the movement of wetted front and the distribution of water and nitrate nitrogen in the wet body were studied under different fertilizer's concentrations and sequences.【Result】The horizontal and vertical movement distance of soil wetted front accorded with power function relation with infiltration time on the un-intersection surface, while it conformed to polynomial functional relation on the intersection surface.The water distribution routine of each treatment was basically the same. On the intersection surface, the water content was not greater than that in other locations of the same soil layer, but the content of nitrate nitrogen was greater than that in other locations of the same soil layer. The interference would affect the migration of wetted front and the nitrate nitrogen content on the confluence surface. When the concentration of fertilizer solution was increased, the concentration of nitrate nitrogen in the wetted body was increased. Under different fertilization-sequence, the distribution of nitrate nitrogen in the wetted body and the edge of the wetted body were different.【Conclusion】It is dominant to conduct comprehensive consideration of the leaching and distribution routine of nitrate nitrogen. Under the condition of point-source interference, compared with the strategy of fertilizer-water, it is suitable to use the strategy of water-fertilizer-water(1/4 W-1/2 N-1/4 W, 3/8 W-1/2 N-1/8 W).