Inorganic Nitrogen Sequestration in Rice-based Ecosystems by Different Times of Fertilization and Tillage Methods

Rice-based ecosystems could be used to sequestrate pollutants from agricultural waste water.Through the simulation test,the consumption of inorganic nitrogen was studied in the paddy field surface water under different fertilization time(regular fertilization time and fertilized one and a half month earlier,which was called early irrigation in the present paper)and different tillage methods(ridge tillage and conventional tillage).It was found that: rice-based ecosystem could effectively reduce the contents of inorganic nitrogen and total phosphorus in paddy field surface water.Compared with the first day,the concentration of NH+4-N in paddy field surface water had reduced by 84.3% after 14 days of irrigation,the concentration of NO-3-N decreased by 64.6% after 21 days of irrigation and total phosphorus reduced by 58.0% at the same time;rice-based ecosystems had a better adsorption in inorganic nitrogen when early fertilization,the concentration of NH+4-N in paddy field surface water were all reached their peak values 1 day after irrigation,with 2.52mg/L in regular fertilization and 1.28mg/L in early fertilization,but the concentration of NO-3-N in regular fertilization reached the peak value of 5.92 mg/L about 3 days after irrigation,and 3.65 mg/L in early fertilization at the same time;there was no obvious difference about adsorption in inorganic nitrogen between ridge tillage and conventional tillage.