EFFECT OF GRAZING AND CULTIVATION ON SOME CHEMICAL-PROPERTIES OF SOILS IN THE MIXED PRAIRIE

Components of the organic matter were studied in soil under grassland dominated by needle-and-thread/blue grama (Stipa comata/Bouteloua gracilis) in good range condition; grassland significantly modified by grazing, dominated by blue grama and in poor range condition; and grassland, dominated by needle-and-thread/blue grama in good range condition, but converted to cropland and under continuous wheat for 4 yr. Concentrations of total organic carbon in the upper 2 cm were 1.39, 2.70, and 1.87%, respectively. The higher organic carbon under blue grama was caused by an active, ramified, fine rootmass which gave rise to most of the monosaccharides being of microbial origin. The monosaccharides in the lower Ap horizon in the cropland were generally of plant origin from incorporated straw. The Ah horizons of the needle-and-thread/blue grama and blue grama sites and the Ap horizon of the cultivated site yielded 244, 696, and 370 μg g-1 organic acids in the alkaline-soluble fraction of the soil, respectively. -from Authors