|Douglas Jr, Clyde|
Submitted to: Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/1998
Publication Date: N/A
Interpretive Summary: Nutrients in runoff and sediment exiting agricultural fields are thought to be major contributors to streams and rivers. The major culprit is thought to be inorganic fertilizers. A series of plots were initiated to evaluate the effect of a winter wheat, spring pea rotation on nutrient loss from a 26 percent north aspect slope near Pendleton, OR. This rotation was compared to a continuous fallow plot. This series of plots would represent the worst case scenario for both soil erosion and nutrient loss, as they were all plowed in the fall and secondary tillage was in an up and down hill direction, and all fertilizer was broadcast by hand on the soil surface. Only a small percentage of the fertilizer nitrogen (N) and phosphorus (P) applied during the five year study was lost in the runoff. Significantly more N and P was lost with the sediment. Trends were for N and P concentrations to be in the following order: winter wheat>spring pea>fallow. However, total N and P loss was in the order: fallow>winter wheat>spring pea, because that was the order of soil loss. Effective control of nutrient loss from winter wheat, spring pea rotations can only be controlled by systems with minimum soil disturbance and residue on the soil surface.
Technical Abstract: Runoff and erosion from cultivated fields are suggested as a major source of nitrogen (N) and phosphorus (P) entering lakes and streams. The amount of these nutrients leaving agricultural fields can be impacted by soil and crop management practices. There is relatively little information on nutrients leaving agricultural fields in the dryland areas of the Pacific Northwest, especially as impacted by different crops and crop rotations. Nutrients in surface runoff and soil leaving a series of plots in Northeast Oregon was evaluated for 5 years. Objectives were to evaluate the effects of a wheat-pea rotation on N and P in surface runoff and eroded soil. Only a very small percentage of N and P were lost in runoff. The primary source of N and P loss was associated with sediment exiting the field. Nutrient loss from agricultural fields can be controlled by controlling soil erosion.