Application of different management measures to reduce runoff losses of nitrogen, phosphorus and copper from orchard in dense river network plain

Abstract: Nitrogen and phosphorus losses from agricultural fields have become more common in China in last two to three decades as a result of increase of fertilizer application. Nonpoint-source pollutants of agricultural production play an important role in eutrophication of lakes and rivers. Thus, controlling the transport of pollutants in runoff is critical to reduce freshwater eutrophication. Dense river network plain region is an intensively managed agricultural production area where concerns over nutrients and heavy metals have been raised. Fruit production within this region is unique in that it often occurs on beds due to the high water table level in this historically wetland area. Beds is designed to support a single row of trees along the top, and large volumes of surface runoff and associated agrichemicals such as nitrogen, phosphorus and copper may leave the production areas in a short period of time due to these drainage features. To investigate the effects of agricultural management measures on runoff losses of nutrients from orchard in the region, in this paper, a plot observation experiment under the conditions of natural rainfall was carried out to study the effects of different measures on runoff losses of nitrogen, phosphorus and copper from orchard in the region. The experiment included five treatments, i.e. control without application of any measures, biological measure with plantation of ryegrass, chemical improvement measure with application of mixture of zeolite and lime powder, engineering measure in that sand sedimentation pit is arranged in the drainage ditch, and comprehensive measures with combined application of biological, engineering and chemical measures. The annual application rates of N, P, K were 1150, 150, and 125 kg/hm2, respectively. Losses of sediment, total and dissolved P, N, and Cu in surface runoff for each of the experimental plots were monitored between January of 2009 and December of 2010. The result showed that application of biological measure reduced runoff volume by 18.6%, and application of biological measure, chemical improvement measure and engineering measure reduced sediment by 52.6%, 16.3% and 38.3%, respectively. Runoff and sediment surface erosion is the main way to carry the nitrogen, phosphorus, copper loss. After biological measure, chemical improvement measure and engineering measure were implemented, the total phosphorus loss is reduced by 38.66%, 18.53%, and 22.68%, and the total copper loss is reduced by 41.4%, 18.4% and 29.9%, respectively. Application of biological measure reduced total nitrogen loss by 23.6%. Reduction effects of phosphorus, copper loss by application of the three measures were greater than that of nitrogen loss. Combined applications of biological, chemical and engineering measures can make the nitrogen, phosphorus, copper loss decrease significantly, which contribute to the protection of water environment around the orchard. These results indicate that all of the biological, chemical and engineering measures are effective management practices that reduce P, N, and Cu runoff from orchard in dense river network plain.