SIMULTANEOUS MEASUREMENT OF RUNOFF AND LEACHING LOSSES OF BROMIDE ANDPHOSPHATE USING TILTED BEDS AND SIMULATED RAINFALL

Small beds packed with soil were used to study intertill soil erosion and chemical transport processes. We compared the partitioning of brom ide and phosphate between runoff and leaching, and related sediments r ates (g/min) to bromide and phosphate concentrations in the runoff. St ainless steel tilted beds (1.0 x 0.5 x 0.1 m) with 2% slope were equip ped with leaching and surface runoff collection funnels. A Tifton loam y sand was hand-packed in the beds to a bulk density of 1.7 Mg/m(3). C hemicals were sprayed uniformly to the soil surface and followed by a 2 h, 10 cm simulated rainfall. Runoff and leaching started after 27 mi n of rainfall and remained constant. Change in sediment rate, and brom ide and phosphate concentrations from the first to the second runoff s ample was related to splash transport. Breakthrough curves for leachin g of bromide and phosphate were different and related to their affinit y for the soil particle surfaces. This experimental technique may be u seful for estimation of pesticide and fertilizer losses from interrill areas.