Experimental Research On Water And Nitrogen Distribution With Single Water Storage Pit Fertigation

Water storage Pit irrigation is a orchard irrigation method which was suitable for the hilly region of north China. The feature of the method ca n meet the need of drought resistance, water holding, water saving and so on. And also can efficiently reduce soil erosion for the orchard. The res earch on water storage pit irrigation method had from indoor condition to the field condition, the studies on soil water movement have tended to b e mature, however, the studies on nutrient transport laws is still at an ele mentary stage. Therefore, conducting experimental research on water and nitrogen distribution could bring important theoretical and practical signific ance for further development of this irrigation method.This paper combines theoretical analysis with the indoor experimental. The horizontal soil column experiment and single water storage pit fertigation experiment were conducted indoor. The water and nitrogen distributions on different irrigation volume (6,8,10L),different soil density (1.3,1.4, 1.47g/cm3) and different fertilizer solution (800,1700,2600mg/L)were studied. The key conclusions are as follows: ],Horizontal soil column experiment:(1) With the soil bulk density increased, infiltration rate,infiltration coefficient and infiltration index are reduced.(2) There existed significant linear relationship(R2>0.97) between advancing distance of wetting front and the time(t1/2) at different soil bulk density.(3) The soil ammonium nitrogen content decreases with the increment of column horizontal distance. At the front end of soil column ammonium nitrogen content increases with the increase of soil bulk density, but at the end of soil column nitrogen content reduces with the increase of soil bulk density.(4) The soil nitrate content increases with the increment in the horizontal direction, and it largely accumulated nearby the wetting front. And at the wetting front soil nitrate cumulant reduces with the increase of soil bulk density.2,Single water storage pit irrigation experiment:(1) The shapes of wetted volume at different bulk densities and irrigation volumes as well as fertilizer liquid densities have similarity, which is that they are all ellipsoidal. The infiltration time is longer as soil bulk density increases, and the smaller the contrary. Also, the infiltration time is longer as the irrigation volume is greater, and the smaller the contrary.(2) The wetting front advancing rate reduces with the increases of soil bulk density, and the advancing distance enlarges with the irrigation volume increases. The relationship between the advancing distance (vertical and horizontal) of wetting front and the time is logarithmic. For the change of irrigation volume and soil bulk density the advancing distance in horizontal always greater than that in vertical, and the less irrigation volume the horizontal advancing distance is more greater than vertical advancing distance.(3) The soil water content in radial decreases with the increment of radial distance, but it increase in vertical with the depth increase. And the higher water content region locates in the depth of 50cm-70cm. The soil moisture potential gradient increases with the increase of the soil bulk density. Increase the irrigation volume will extend the higher water content region and make the water content peak deeper. The fertilizer level has no observably effect on the water distribution.(4) The soil nitrate content increases with the distance increases in radial direction, and the higher nitrate content region locates in the 40cm-70cm depth. Because of the nitration reaction near the pit wall, the soil nitrate content increases there.(5) The total content of nitrate nitrogen in the wetted volume decreases with the increase of the increase of soil bulk density. With the increase of the irrigation volume the nitrate nitrogen content at the boundary of the wetted volume increases, however, the total content of nitrate nitrogen in the wetted volume decreases. Increase the irrigation volume will result in the nitrate nitrogen distributed unevenly, which go against the plant uptake. With fertilizer concentration increases, the nitrate concentration in radial and vertical direction also increase unitarily. (6) The soil ammonium distribution decreases with the increment of radial distance. The soil ammonium distributes uniformly in vertical, and it gets a decline in the 70cm depth. The soil ammonium content is less near the pit wall. Besides this, the ammonium content in the wetted is higher than the background value.(7) The ammonium content in the wetted volume increases with the increase of the soil bulk density. Increase the irrigation volume and fertilizer concentration will lead to nitrate concentration in vertical and radial direction also increase unitarily.