膜孔肥液多向交汇入渗土壤硝态氮运移特性试验研究

Experimental Research on Soil Nitrate Nitrogen Transport Characteristics Under Film Hole Bilateral Interference Infiltration of Fertilizer Solution

通过室内试验,研究了相同供水条件下不同取土时间的土壤NO_3^--N在湿润体剖面的分布及运移特性。结果表明:在供水入渗阶段,土壤NO_3^--N浓度的最大值出现在土壤表层;土壤NO_3^--N浓度锋运移距离和最大值随时间的延长而增大。供水停止时,随着与膜孔中心距离的增加,土壤NO_3^--N含量逐渐减少;膜孔中心两侧的湿润面在土体表层12 cm范围内NO_3^--N含量变化梯度较小,湿润锋处的土壤NO_3^--N含量变化梯度较大;先交汇中心界面的NO_3^--N含量比后交汇中心界面的NO_3^--N含量稍大;土壤垂向含水率在土壤表层10 cm范围内相差较小,且分布均匀;在10 cm以下变化梯度较大,各中心垂向土壤含水率的变化梯度为:ab>DC>AB;垂向土壤NO_3^--N含量在表层8 cm范围内相差较小,且分布均匀;810 cm范围内,后交汇中心ab的土壤NO_3^--N含量比AB和DC中心的稍小;10 cm以下的土壤NO_3^--N含量变化梯度为:ab>DC>AB。进入再分布阶段,土壤NO_3^--N浓度锋运移距离随时间继续延长,湿润土体内NO_3^--N浓度的分布逐渐均匀;随时间的延长,土壤剖面NO_3^--N浓度的最大值逐渐减小,且位置逐渐向下迁移。说明对于灌水定额较小的膜孔肥液多向交汇入渗,NO_3^--N主要存在于土壤表层,对地下水造成污染的可能性较小。

Based on lab experiments, the distribution characteristics and transport characteristics of soil NO3-N of wetting body section under the same water supply with different removal times are studied. The results show that the maximum value of NO3-N concentration lies in the surface layer and the soil NO3-N concentration peak transport distance and maximum value increase with the time increase in the process of water supply. By the end of water supply, soil NO3 -N content gradually reduces with the increased distance from the film hole center. Soil NO3-N content gradient of wet surface on both sides of the film hole center within the scope of 12 cm in the surface layer is smaller, soil NO3 -N content gradient of wetting front is larger. Soil NO3-N content of first center interface is slightly bigger than that of later center interface. Soil water content of vertical in the soil surface layer of 10 cm scope is a little different. Soil water content gradient below 10 cm is larger, the soil water content change gradient of central vertical is： ab 〉 DC 〉 AB. Soil NO3-N of vertical in soil surface layer of 8 cm scope is a little different. In the scope of 8 cm to 10 cm, soil NO3-N content of ab is less than that of AB and DC. The soil NO3-N gradient below 10 cm is： ab〉DC〉AB. In the process of redistribution, soil NO3-N concentration peak transport distance continued to increase with time. The distribution of the soil NO--N concentration becomes relatively uniform in the whole wetting soil body. The maximum NO3-N concentration decreases with the redistribution time increasing and the position migrating downward. The resuhs illustrate that soil NO3-N mainly exists in the surface soil for the smaller irrigation quota under fihn hole bilateral interference infiltration of fertilizer solution, so the possibility of groundwater pollution caused by the fihn hole irrigation is smaller.