Dynamic changes of nitrogen losses through drainage with controlled and mid-gathering irrigation during typical rainstorm events in southern China

摘要

The experiments were conducted to investigate the effect of nitrogen losses through the paddy field runoff by comparison of controlled and mid-gathering irrigation and conventional irrigation of rice during typical rainstorm events in southern China.Statistical analysis on water samples showed that flow happened after the field soil was filled with rainfall water, and the controlled and mid-gathering irrigation was much later than that of conventional irrigation. The drainage volume didn't change much during runoff, while three forms of dissolved nitrogen varied greatly under two irrigation modes. Compared with conventional irrigation, controlled and mid-gathering irrigation had a shorter drainage time under the same conditions, and this indicatedthat paddy field could store more water during the rainfall events. According to the results, drainage volume and duration under conventional irrigation were, respectively, 1.2 and 1.5-2.5 times of those in controlled and mid-gathering irrigation. Also,it was suggested that nitrate nitrogen (NO~3-N) contributed most to soluble nitrogen losses during runoff. Dynamic changes of ammonium nitrogen (NH4+-N) and nitrate nitrogen (NO"3-N) concentration were not much the same in the two modes during rainfall process. In general, the controlled and mid-gathering irrigation can significantly reduce emissions of non-point source pollution. Besides, the change trend of pollutants provided a certain theoretical basis for irrigation-drainage mode formulation.