The Impact of Different Fertigation Practices and Initial Soil Salinity on Soil N and Salinity Transport

For studying the impact of different fertigation practices and initial soil salinity on soil N and salinity transport, large Plexi-glass columns (18.2 cm in diameter and 100 cm long) assembled from sandy loam (Inner Mongolia) and saturation optimum design were employed to simulate a range of initial soil salinity conditions in soil profile and fertigation practices. (4~8 L) solution with 20 g urea dissolved was applied evenly and slowly to the surface of each column. Nitrate and ammonium nitrogen in soil and discharge from the outlet were sampled and the electrical conductivity of soil and the chloride ion concentration of discharges were also measured. Findings from this study include: (1) high initial salinity in soil had a certain impact on the changes of water content of vertical soil section with the time being after large amount of water irrigation and it might increase the rate of infiltration; (2) the amount of irrigation water significantly affected the transport of soil salinity; (3) high soil salinity content was likely to promote the conversion of urea nitrogen to ammonium nitrogen and it might also play an active role in ammonium nitrogen accumulation in drainage; (4) There is a sound linear relation between the cumulative content of chloride ion and that of nitrate nitrogen in the drainage and soil profile (r2 = 0.8221 and 0.7442).