Output of water, suspended sediment, and phosphorus and nitrogen forms from a small agricultural catchment

Abstract The outputs of water, suspended sediment, and phosphorus (P) and nitrogen (N) forms from a small agricultural catchment in the northern Tararua Ranges were studied for 1 year. Streamflow and rainfall were recorded. A water balance estimated for the catchment indicated that deep percolation was minimal. During the study year approximately 26% of total rainfall was discharged as streamflow. An attempt was made to identify and quantify the inputs of P and N forms to the catchment. Phosphate fertiliser application, N‐fixation by clovers, and rainfall were considered the major sources of inputs of P and N forms. The output of suspended sediment was 1.4 × 10 3 kg/ha. Significant quantities of P and N output were associated with suspended sediment. Of the annual loss of total P (1.6 kg/ha), 76% was in the particulate form. The annual output of total N was 5.2 kg/ha, 14% in the particulate form.