EFFECTS OF SUBSOIL LOOSENING ON SOIL PHYSICAL-PROPERTIES, PLANT-ROOT GROWTH, AND PASTURE YIELD

Subsoil loosening of an 8-year-old dryland pasture soil (Templeton sil t loam) at either of two depths (27 or 47 cm) resulted in a significan t (P < 0.1) decrease (>10%) in soil bulk density and a concomitant inc rease in soil porosity compared with undisturbed soil. The hydraulic c onductivity of the loosened soil was significantly (P < 0.05) greater than that of the undisturbed soil, reflecting the increased pore conti nuity within the depth of loosening. These more rapid drainage rates r esulted in a drier soil profile at the start of spring, 10 months afte r subsoil loosening. These improved soil physical conditions permitted more rapid root growth and the development of a more extensive pastur e root system with a significantly (P < 0.1) greater (36%) root length below 30 cm depth. Subsoil loosening resulted in significant increase s in pasture production over the first 3 months of spring (August-Octo ber).