Abstract:

【Objective】 This study was to establish the load estimation method of nitrogen and phosphorus loss from agriculture which was suitable for irrigation district, in order to simply and effectively calculate the agricultural non-point source pollution in irrigation district. 【Method】The nitrogen and phosphorus loss from agriculture in Ningxia irrigation district were assessed by Johnes export coefficient method. The traditional Johnes export coefficient method had been improved in accordance with the characteristics of the irrigation area, in which the irrigation factor on the impact of the output was added. 【Result】 The results showed that TN (total N) factor was 0.9556 and TP (total P) was 0.8776 in Ningxia irrigation district in 2006; according to traditional model, TN rate was 20 296.29 t and TP was 1 092.02 t in 2006, while according to improved model, TN load was 19 395.33 t and TP was 958.30 t in 2006. Compared with the traditional model, the relative error of TN rate of the improved model reduced by 5%, and TP rate reduced by 13%. 【Conclusion】 It is concluded that the predicted result of the improved model is more approximately in accordance with the actual pollution of irrigation area than the traditional model, that is to say the improved model is applicable to irrigation district.

Key words: irrigation district, agricultural non-point source pollution, export coefficient method, rate estimation