POLLUTION POTENTIAL OF MANURE SPREAD ON FROZEN GROUND

The nutrient content of snowmelt runoff was measured to determine the contribution of manure applied to frozen plots on which corn (Zea mays L. ) and alfalfa (Medicago sativa L. ) were grown. Nutrient concentrations in spring runoff were high from all manured plots, compared to unmanured plots, but total nutrient losses varied greatly depending on type of soil surface receiving the manure and time of application. Up to 20% of the N and 16% of the ortho-P in the manure was carried away in spring runoff from alfalfa plots while no more than 3% of the N and 4% of the ortho-P was lost from manured fall-plowed plots. Applying manure to frozen plowed land reduced soil losses 100% and runoff up to 80%.