Effect of Mesquite on Physical and Chemical Properties of the Soil

Abstract

Soil under the crown of mesquite trees was compared to soil from adjacent openings at three depths for several physical and chemical properties near Tucson, Ariz. Bulk density was lower in soil under mesquite but increased with depth in that location. Organic matter, total nitrogen, total sulfur, and total soluble salts were up to three times greater in the surface 0 to 4.5 cm of mesquite soil than in open soil but declined with increasing depth to levels approximately the same as in open soil. Total potassium was higher under mesquite but increased with depth. Total phosphorus and hydrogen ion concentrations were the same in soil under mesquite as in soil from open areas. Results suggest that mesquite trees function to improve soil conditions under their canopies by redistribution of nutrient ions from areas beyond the canopy to areas beneath the canopy. This process helps to explain the greater abundance and improved growth of perennial grasses observed under mesquite. It also helps to explain grazing patterns and responses on desert grassland.