ORCHARD GROUNDCOVER MANAGEMENT IMPACTS ON SOIL PHYSICAL-PROPERTIES

This study was conducted to compare various orchard groundcover manage ment systems (GMSs)-including a crownvetch ''living mulch'' (CNVCH), c lose-mowed (MWSOD) and chemically growth-regulated (GRSOD) sodgrasses, pre-emergence (NDPQT) and tw,vo widths of post-emergence (GLY1.5 and GLY2.5) herbicides, hay-straw mulch (STMCH), and monthly rototillage ( tilled)during the first 6 years in a newly established apple (Malus do mestica Borkh.) planting. Mean soil water potential at 5 to 35 cm deep varied substantially among treatments each summer, and treatment x ye ar interactions were observed. During most growing seasons from 1986 t o 1991, soil water availability trends were STMCH > NDPQT > GLY2.5 > G LY1.5 > tilled > GRSOD > MWSOD > CNVCH. Soil organic matter content in creased under STMCH, CNVCH, and MWSOD and decreased under NDPQT and ti lled treatments. Water infiltration and saturated hydraulic conductivi ty after 4 years were lower under NDPQT and tilled, and soil under STM CH and GRSOD retained more water per unit volume at applied pressures approximating field water capacity. Mid-summer soil temperatures at 5 cm deep were highest (25 to 28C) in tilled and NDPQT plots, intermedia te (22 to 24C) under GRSOD, and lowest (16 to 20C) under CNVCH and STM CH. These observations indicate that long-term soil fertility and orch ard productivity may be diminished under pre-emergence herbicides and mechanical cultivation in comparison with certain other GMSs.