Bromide transport under sprinkler and flood irrigation for no-till soil condition

Understanding the influence of irrigation methods on solute transport is es sential to properly manage chemical use in agricultural soils. In this stud y, we compare the transport of a conservative solute (bromide) under sprink ler and flood irrigations on a sandy clay loam (mixed Ustollic Haplargid) u nder no-till condition. After spraying 148.8 kg/ha of KBr on the surface, a pproximate to 25 cm of irrigation water was applied in six increments over two months as flood irrigation on one plot and as sprinkler irrigation on a nother plot. The net applied water (NAW = irrigation + precipitation - evap oration) was similar for both plots, which allowed the comparison of the Br profiles for the two types of irrigation. Water content and Br concentrati on were sampled at 5, 19, 34, and 68 days after chemical application. The recovered mass of Br and the location of center of mass were comparable for the two types of irrigation. The spread around the center of mass, how ever, was higher for the flood-irrigated plot. On the flood-irrigated plot, more mass leached below the depth of 90 cm, with the differences being sta tistically significant. The velocity of the Br center of mass was consisten tly 10%-20% larger than the piston displacement velocity. Dispersion and ve locity coefficients varied substantially between sampling time. A recent qu asi-steady solution of the convection-dispersion equation [M.H. Nachabe, L. R. Ahuja, Quasi-analytical solution for predicting the redistribution of su rface-applied chemicals. Trans. ASAE 39(5) (1996) 1659-1664], which account s for variable flow and dispersion, simulates the Br profiles fairly well. (C) 1999 Elsevier Science B.V. All rights reserved.