NUTRIENT TRANSPORT IN RUNOFF FROM FEEDLOTS AS AFFECTED BY WET DISTILLERS GRAIN DIET

Distillers byproducts can serve as valuable sources of protein and energy for beef cattle. However, the water quality effects of the use of distillers byproducts in cattle rations are not well understood. The objectives of this study were to: (1) measure soil properties and nutrient transport in runoff from feedlot surfaces as affected by corn‐based and wet distillers grain diets, (2) compare the effects of unconsolidated surface materials and consolidated subsurface materials on feedlot soil characteristics and runoff nutrient transport, (3) determine if runoff nutrient transport from feedlot surfaces is correlated to selected feedlot soil properties, and (4) identify the effects of varying runoff rate on nutrient transport. Simulated rainfall events were applied to 0.75 m wide by 2 m long plots. Concentrations of calcium, copper, loss on ignition, magnesium, organic‐N, potassium, total N (TN), and zinc in the feedlot soil materials were significantly greater within the pens where cattle were fed a corn‐based diet rather than a diet with distillers grain. The pens where cattle were fed distillers grain contained significantly greater amounts of Bray‐1 P. Surface condition did not significantly affect any of the measured feedlot soil properties except potassium content. No significant differences in measured runoff water quality parameters were found between the corn‐based and wet distillers grain treatments. Runoff measurements of NH4‐N, TN, NO3‐N, total dissolved solids, and electrical conductivity were each significantly correlated to seven or more feedlot soil parameters. Each of the measured water quality parameters were significantly influenced by runoff rate