Bromide Transport under Contour Hedgerow Systems in Sloping Oxisols

Abstract

AbstractContour hedgerows promote infiltration, thereby reducing runoff and soil erosion on sloping lands. The increase in infiltration could increase the leaching of mobile chemicals. The objective of this study was to determine the effect of hedgerows on Br‐ transport in two Hapludox soils with 21 to 30% slope in the Philippines. In Exp. 1, KBr at the rate of 200 kg Br‐ ha‐1 was broadcast in June 1991 at corn (Zea mays L.) planting on (i) the alleyways of plots with pruned hedgerows of Gliricidia sepium (Jacq.) Klunth ex Walp. and paspalum (Paspalum conjugatum Bergius) (hedgerow treatment) and (ii) open field plots (control). In Exp. 2, KBr was applied at the same rate as in 1991 in strips in the hedgerow and control plots that had not received the KBr application the previous year. After Br‐ application, Br‐ was analyzed in hand‐augered soil samples at increments to 105 cm and in soil solution samples taken with suction lysimeters at the 30‐, 60‐, and 90‐cm depths. Estimated pools of Br‐ (kg ha‐1) at a given depth were usually less for the suction lysimeter than for soil samples, possibly due to percolating water bypassing Br‐ in soil aggregates above the depth of lysimeter sampling. After about 500 mm of rainfall, 50% of the Br‐ had leached below the 30‐cm depth in the hedgerow plots. Slightly greater lateral, but less vertical, Br‐ movement occurred for the control. If NO3 leaches to or below the observed Br‐ leaching depths, it would become unavailable to acidsensitive food crops displaying shallow rooting depths.