An Investigation On Water And Nitrogen Transport And Transformation In Soils Under The Irrigation With Reclaimed Waste Water

For investigating the water and nitrogen use efficiency and water and nitrogen dynamics in root zone when irrigation with reclaimed waste water, an experiment has been conducted in field with silt loamy soil and the summer corn, winter wheat were used as test crops from 2002 to 2003. Combining the different irrigation levels and fertilizer levels, 4 treatments irrigation with reclaimed wastewater and 3 treatments irrigation with fresh water were set in this experiemnt.First of all, an analysis of experimental data was conducted, results indicate that the influences of irrigation rate, fertilizer level and irrigation water quality on plant height, leaf area index and yield are relatively distinguishable.High irrigation rate and fertilizer level in the treatment of irrigation with reclaimed water can enhance thecrop height, leaf area index and yield of summer corn.Lower fertilizer level couple with moderate irrigation rate for irrigation with reclaimed waste water has the highest nitrogen use efficiency, at the same time the highest water use efficiency occurs on the treatment of moderate fertilizer level coupling with moderate irrigation rate of irrigation with reclaimed wastewater.Secondly, a lumped parameter model was used in this paper to simulate the concentration of nitrate in root zone.Data set collected form a field experiment with six small plots was used to calibrate and validate the model.After selecting parameters from relative literatures, the data sets from two of the six plot was used to optimize the coefficient of plant uptake rate μ with minimum relative errors between the measured and calculated nitrate concentration as its indicator.Simulation was then conducted.Results show that the calculated nitrate concentration by the model agrees well with the measurement, which implies that the model and the parameters both selected form the literature and determined by optimization are capable of being used to simulate and predict the nitrate dynamic in root zone. Sensitive analysis of model was also conducted, and the result indicates that LPM is mostly sensitive to the coefficient of nitrification rate k2 and the coefficient of plant uptake rate μ.The calculated nitrate concentration in the root zone increases with the increase of the coefficient hydrolysis rate k1 and the coefficient of nitrification rate k2, while decreases with the denitrification rate k3 and the coefficient of plant uptake rate μ..At last, a mathematical model for modeling water movement and nitrogen transport and transformation was established with considering salt stress effect on water and nitrogen uptake by plant root.Simulation of water and nitrogen dynamics in winter wheat growth field was conducted, it is shown that the silmulated results agree well with the measurements of soil moisture, NH4+-N and NO3--N for most of the simulation time, which then means this model is applicable to simulate water and nitrogen dynamics of irrigation with reclaimed waste water.