RATES OF SOIL CHEMICAL CHANGES WITH ELEVEN ANNUAL APPLICATIONS OF CATTLE FEEDLOT MANURE

Abstract

The rates of change of several soil chemical properties in response to repeated annual applications of cattle feedlot manure, in a long-term experiment, were determined from 1974 to 1984. Manure was applied at 0, 30, 60 and 90 Mg ha−1 and 0, 60, 120 and 180 Mg ha−1 (wet weight) to nonirrigated and irrigated Dark Brown Chernozemic soils, respectively, using three tillage methods of incorporation. Soil acidity (pH), estimate of soluble salts (EC), sodium adsorption ratio (SAR), and accumulation of Na, Ca + Mg, SO4 and Cl in the soil were determined annually. Regression analyses were used to determine the rates of accumulation of these parameters with time. The rates of change with time were mostly linear and varied with the level of manure applied and irrigation regime. The soil became more acidic with time. Soluble Na and Cl increased at rates similar to or less than those applied, and soluble Ca + Mg increased at rates greater than those applied. Changes in the soluble SO4 were poorly correlated with time. Regression analyses from 1974 to 1977 and 1978 to 1984, under irrigated conditions, indicated that the rates of change were generally less in the latter period. Thus, the losses of applied constituents were higher in the second period than in the first period under irrigation. However, various soluble constituents from the annually applied manure accumulated in the soil even at the recommended rate. These findings indicate that sustained agricultural production of this land with annual application of manure is in question, and the potential for problems due to leaching of various soluble salts and nutrients to groundwater is increased. Key words: EC, soluble salts, leaching, salinization, pH