Effects of Irrigation Modes on Nitrogen and Phosphorus Concentra-tions of Field Ponding Water and Rice Growth Traits During Fertil-ization
In order to explore the drainage utilization in the paddy field of Liaohe Delta region and reveal whether irrigation-drainage recycle has the risk of causing non-point source pollution,we monitored N and P concentrations of ditch water and determined the effects of irrigation modes on N and P concentrations of field ponding water and rice growth traits during fertilization.The results showed that TN concentrations reached the peak values of 4.49 mg/L and 15.61 mg/L in the irriga-tion ditch water and the drainage channel water at the time of the second monitoring,followed by a decrease,which was in accordance with that in the period of basal fertilizer soaking.The concentra-tions of TN and TP in the drainage channel water were higher than those in the irrigation ditch water.During the critical fertilization period,the drainage of field ponding water should be controlled for the reduction of N and P concentrations in the drainage channel water.TN concentrations of field ponding water peaked on the 3rd and then stabilized 10 days after both basal fertilizer and topdress-ing,with 0.65-2.42 mg/L higher in the irrigation-drainage recycle treatment than the conventional ir-rigation.There was a positive correlation between TN concentrations of field ponding water and N fer-tilizer application.TN concentrations 1 day after irrigation were higher in the irrigation-drainage re-cycle treatment than the conventional one,whereas 3 days after irrigation there was no significant dif-ference between these two treatments.Likewise,no significant difference for TP concentrations ex-isted between these two treatments.Irrigation-drainage recycle increased the risk of N and P loss,in-dicating that we should control the drainage from paddy field within 3 days.Within 10 days after basal fertilization,there was also a risk period for nitrogen and phosphorus loss.Irrigation-drainage recycle combined with a 22％reduction in N fertilizer can promote effective tillering and increase rice yield.Reasonable utilization of irrigation-drainage recycle can be applied to rice production and reduce the risk of N and P loss.
irrigation modefield ponding waternitrogen and phosphorus lossricegrowth traits
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