Microbial Transport as Affected by Residue Cover and Manure Application Rate

Abstract

Abstract. Manure is applied to cropland areas with varying surface cover to meet single- or multiple-year crop nutrient requirements. The objectives of this field study were to (1) examine microbial transport following land application of manure to sites with and without wheat residue, (2) compare microbial loads following land application to meet the 0, 1, 2, 4, and 8-year P-based requirements for corn, and (3) evaluate the effects of rainfall simulation run on microbial transport. Manure was added and incorporated by disking plots that were 0.75 m wide by 2.0 m long. Three 30 min simulated rainfall events, separated by 24 h intervals, were then applied at an intensity of 70 mm h-1. Plots containing wheat residue had a total coliform load of 12.6 log CFU ha-1, which was significantly greater than the 12.4 log CFU ha-1 measured on the plots without wheat residue. The plots with and without wheat residue had transport rates of and enterococci that were not significantly different. The plots on which manure was added at rates varying from 5.4 to 42.8 Mg ha-1 had counts of total coliforms and enterococci that were not significantly different. Rainfall simulation run did not significantly affect measurements of phages, total coliforms, or enterococci. Transport of selected microbes was found to be significantly affected by residue cover, manure application rate, and rainfall simulation run. Keywords: Bacteria, Cattle manure, E. coli, Feedlots, Land application, Manure management, Manure runoff, Microbial, Microorganisms, Runoff.