SOIL-WATER AND SOIL PHYSICAL-PROPERTIES UNDER CONTOUR HEDGEROW SYSTEMS ON SLOPING OXISOLS

Hedgerows planted along the contour on steep lands in the humid tropic s reduce soil erosion and build terraces over time, The objectives of this study in two Hapludoxes in the Philippines were to evaluate chang es after 4 years in soil properties and soil water relations on transe cts perpendicular to the cropped alleys between four grass and tree he dgerow systems and a control. Hedgerow plants included Gliricidia sepi um, Paspalum conjugatum, and Penisetum purpureum. Soil properties eval uated as a function of position in the alley (upper, middle, or lower elevation in an alley) included bulk density, mechanical impedance, so il water transmissivity, water retention, soil water pressure, and soi l water content. In general, soil properties were not affected by hedg erow system, but were affected by position in the alley, Nearness to t he hedgerow, but not hedgerow species, affected soil water distributio n (P = 0.05). Plant available water at the 10-15 cm depth was 0.16 m(3 ) m(-3), 0.13 m(3) m(-3), and 0.08 m(3) m(-3) for the lower, middle, a nd upper alley position, respectively, Water transmissivity decreased from 0.49 mm s(-1) in the lower alley to 0.12 mm s(-1) in the upper al ley, The lower soil water contents and soil water pressures in and nea r the hedgerows confirmed competition for water between the hedgerow s pecies and the food crop in the alley, a condition that is expected to suppress food crop production.