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

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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.