The Effect Of Distribution Of Nitrogen By Fertilization In Different Period Under Drip Irrigation

Most of the domestic and foreign scholars set different fertilizer gradient, fertilizer at different stages,and cucumber in different conditions such as mixing proportion based on the important role for the growth of crops and fertilizer application problems in irrigation technology,and the research focus on in the study of fertilization system in the process of crop growth,but the space-time distribution features of nitrogen under the condition of drip irrigation research are relatively few. Nitrogen is one of the required elements in plants, and the nitrogen assimilated by plant is usually higher than that of other mineral elements, so nitrogen often become the main elements of limiting plant growth, at the same time, most of the nitrogen absorbed in the form of NO3--N and NH4+-N in the growth process of the plant. In order to reduce the loss in the transport process of water and fertilization and improve its use efficiency, different period fertilization under drip irrigation to research the space-time distribution features of nitrogen in the soil. The wetting layer depth is designed to 30 cm, wetting radius is 20 cm, the biggest irrigation is 8L after calculation, the whole time of drip irrigation is 240 min. The designed fertilization including the regular quantity(20g) and the other(80g). Design for nitrogen application under the four different time processing as follows: A)whole irrigation and fertilization,B)using fertilization in first half of the whole period,and irrigating during the rest of the time, C)using fertilization in second half of the whole period, D)irrigating in first quarter of the time, then using fertilization in the following half of the time,using irrigation at the last. The sampling time is 1,3,5,7day after after irrigation and fertilization, sampling points respectively from infiltration transverse distance of 5 cm, 15 cm,20 cm, away from the surface of the vertical of 0 to 5, 5-15, 15 to 25, 25-35 cm, explore the drip irrigation condition and NO3--N and NH4+-N in time and space distribution under different-time fertilization, by doing so can be more intuitive understanding of nitrogen in the soil migrationchange regular and its space-time distribution characteristics, specifically the following main conclusions:(1) With the passage of time, the NO3--N content in the moist body showed a trend of decrease the first increase after the treatment, and it was always enlarged before 5th day,reduced in 7th day. The transformating rate of NH4+-N was relatively fast,the nitrification was most strong on the third day after irrigation and fertilization,and the rate decreased sharply from third day to fifth. NO3--N and NH4+-N show the shift trend, It shows that some of the NH4+-N are converted into NO3--N via nitrification, this is also the reason for the peak value of NO3--N in the fifth day.Although the fertilizer rate is the same under the condition of the integration of irrigation water, the size and location of NO3--N and NH4+-N peak value are obviously different caused by the different fertilization time in the soil body. It presents that NO3--N and NH4+-N are mainly distributed in the edge of the moist soil body area by the early stage of the irrigation fertilization.NO3--N and NH4+-N are mainly distributed in the central regions of the moist soil body by the late stage of the irrigation fertilization. The high density of NO3--N concentration distribution in the irrigation emitter under the treatment of A and C, namely 0-15 cm soil layer and horizontal direction 0-15 cm range, showing obvious table cohesion. The high density of NO3--N mainly located in horizontal 15 cm distance and vertical depth 25 cm from irrigation emitter by B-treatment, and it is located in horizontal 15 cm distance and vertical depth 15 cm from irrigation emitter under the treatment of D. The space migration distance is smaller of NH4+-N relative to NO3--N, the NH4+-N are mainly distributed in the 0 to 15 cm layer under A and B treatment, and it is distributed in the 0 to 5cm under C, the NH4+-N of 5-15 cm layer is higher. On the whole, there is certain adsorption effect to nitrogen in the soil on the one hand, and there are the real phenomenon that fertilizer following with mizuhashiri.The NO3--N appears the rise of the corresponding when increasing nitrogen fertilization,when the concentration of liquid fertilizer is 10 g/L, no matter firstly fertilization, or irrigation firstly, the accumulation of nitrate nitrogen located in edge of wet body. And it can be very good to keep in the middle of the soil layers by controlling the middle period fertilizer nitrate, thus avoiding waste and pollution caused by leakage of fertilizer. High nitrogen fertilization can cause the soil nitrogen concentration is too high and affecting the water use efficiency of crop.Therefore, fertilization way should use a small amount of multiple patterns to improve water use efficiency under the condition of cucumber in irrigation.