Nitrate and Salt in Soils and Ground Waters from Land Disposal of Dairy Manure

Abstract

Abstract The NO 3 ‐ contents of soils and ground waters underneath lands used for disposal of manures from dairies in the Chino‐Corona Basin were determined. Soil and water samples were taken from 15 holes drilled to the top of water table in sites representing corrals, irrigated croplands, and pastures used as disposal areas. Considerable amounts of NO 3 ‐ and salt were found in soil profiles underneath the disposal areas, although the magnitude was not as high as in profiles under corrals. Average NO 3 ‐ ‐N concentrations in waters sampled from water tables were 26, 57, 45, and 74 ppm for control (undisturbed), corral, cropland, and pasture sites, respectively, exceeding the PHS recommended limit of 10 ppm NO 3 ‐ ‐N for safe drinking water. Domestic well waters pumped from deeper aquifers averaged 6 ppm of NO 3 ‐ ‐N. Contributions of NO 3 ‐ ‐N to ground waters, as indicated by deep soil samples, on a per unit area basis, tended to be: corral > pasture > cropland. Existing conditions in the study area need some modifications if acceptable quality of the ground waters is to be maintained.