|Koehn, A - WASHINGTON STATE UNIV|
Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: August 1, 2000
Publication Date: N/A
Technical Abstract: Dairy industry expansion in southern Idaho has increased manure production and manure application to irrigated cropland. This raises concerns that manure-derived nutrients may contaminate surface waters. We hypothesized that nutrients from fresh manure applied to fields can be lost in furrow irrigation runoff. Three irrigations were monitored on a field with 1.5% slope that had received no manure in 14 y, and a field with 4% slope and a current-year, 45-Mg/ha, disked-in manure application. Furrow irrigation inflows and outflows were measured, and runoff samples collected for analysis of sediment, nitrate-N, molybdate- reactive-P, and total-P, Furrow streams in the manured field had lower runoff rates (4.7 L/min vs 9), but contained more sediment (13.5 g/L vs 2) than that of the nonmanured field. Flow-weighted runoff-nutrient concentrations from the manured field were 5 to 8 times those of the nonmanured field. Total-P was associated with runoff sediment. Hence, the greater total-P in runoff from the manured field (compared to the nonmanured treatment, may in part be caused by increased runoff sediment. Unlike runoff total-P concentrations, however, runoff nitrate-N was not correlated with sediment load. This suggests that the application of fresh manure to the field directly increased nitrate-N losses in furrow irrigation runoff.