Abstract:

Field insitu investigation was conducted to study the sloping land pathways and processes of water and nutrient movement in the Citrus Orchard in Danjiangkou Reservoir area,China.Three mulching treatments were adopted in the runoff plots,including no mulching (CK,conventional practice) as control,rice straw mulching (SM) and plastic film mulching (FM).Nitrogen (N) and phosphorus (P) losses with surface runoffs were measured during the experimental period.Results indicated that the runoff was increased by the FM treatment,but was not affected much by the SM treatment when compared with the CK treatment after each rainfall.Both N and P losses were presented with runoffs in all of the plots,and the losses were much more in the FM treatment,with the loss ratio of TN and TP being 0054% and 0064% respectively,than that in the SM treatment.Much more nitrogen was lost than phosphorus from the citrus orchard soil with the rainfall runoffs,and the soluble nitrogen occupied much of the total nitrogen loss,primarily in the nitrate form rather than the ammonium form.It was concluded that straw mulching practice was good to keep soil nutrient,specially the nitrogen,in citrus orchard on the sloping land from being lost with rainfall runoffs,and it could reduce the risk of nitrogen pollution to the Danjiangkou Reservoir.