Drainage losses of nitrate from paddy fields influenced by two periods of midseason drainage

Midseason drainage (MSD), a water management method in paddy fields, supplies oxygen to soil and prevents accumulation of potentially toxic substances to root growth. In this research, effect of two MSD periods on nitrate losses from consolidated paddy fields of Sari Agricultural Sciences and Natural Resources University were investigated in a rice growing season from May- July 2014. The fields consist of a bi-level subsurface drainage system with drain spacing of 15 m and drain depths of 0.65 and 0.9 m as alternate depths (Bilevel) and surface drainage system with drain depth of 1.2 m (Control). For MSD, the paddy plots were drained during two periods: 25- 35 days after transplanting (DAT) and 42- 49 DAT. Measurement of drainage discharge and nitrate concentrations of drainage effluents was made in these periods. Total drainage losses of nitrate in Bilevel and Control were, respectively, 1.39 and 1.99 kg ha-1 during drainage periods. Based on the results, subsurface drainage caused lower pollution of surface water resources in the study area due to lower nitrate losses compared with surface drainage

کلیدواژه ها:

Environmental pollution ، Midseason drainage ، Nitrate losses ، Paddy field ، drainage