Fate of potassium in dairy cow urine applied to intact soil cores

Abstract

Following an application of dairy cow urine to intact cores of four contrasting soil types, the redistribution of urine potassium (K) as a result of leaching, plant uptake, and soil adsorption was investigated. In climatic conditions that simulated those of August/September in the Manawatu region, 5-39% of the applied urine K immediately moved by macropore flow to beyond the 15cm depth of soil. Leaching losses of K from 90 mm of simulated rain events, which followed the urine application, were smaller than K losses immediately following the urine application and accounted for only 2-6% of the applied urine K. The urine K adsorbed by the soil was retained mainly in the 0-7.5 cm depth of soil in an exchangeable form. During the 30-day period of the experiment less than 10% of the urine K was recovered in the herbage. Overall these results suggest that, irrespective of soil type, a major loss of K occurs as a result of macropore flow of the urine following a urination event. The concentration of K in the urine had little effect on the proportion of the applied K that appeared in the leachate. © 1990 Taylor & Francis Group, LLC.