RUNOFF AND LEACHING OF CROP NUTRIENTS FROM SOIL IN TILTED BEDS AS INFLUENCED BY 3 RATES OF DAIRY LAGOON EFFLUENT

The objective of this study was to determine the effect of lagoon effl uent application on losses of crop nutrients in runoff and leaching so lutions. Tilted beds, packed with Fuquay sand and equipped with runoff and leachate collection funnels, were utilized, Lagoon effluent was a pplied at three rates. Simulated rainfall (5 cm h(-1)) was applied for two hours, and runoff and leachate were collected. Increasing effluen t application rate led to increased NO3-N leaching, decreased PO4-P ru noff, and increased Mg leaching. The highest application rate resulted in buildup of P and K in soil, but N losses exceeded applied amounts at ail application rates. We propose that as effluent application rate increased, the large K concentration in the effluent exchanged wi th soil Ca and Mg on exchange sites, leading to increased Ca and Mg conce ntrations in soil solution, Increased Mg concentration in soil solutio n led to increased Mg leaching. However, the Ca2+ ion probably formed the ion pair CaHPO4 degrees with phosphate from the effluent, and read sorbed to soil colloids as an ion pair. thus diminishing P runoff.