Mobility and half-life of bensulide in agricultural soil.

Environmentally and economically viable agriculture requires the use of cultivation practices that maximize agrochemical efficacy while minimizing their off-site movement. Bensulide [O, O-diisopropyl S-2-phenylsulfonylaminoethyl phosphorodithioate] is one of the few herbicides from the organophosphate group used for control of weeds that threaten numerous crops. A field study was conducted on a silty-loam soil of 10% slope at Kentucky State University Research Farm to monitor off-site movement and persistence of bensulide in soil. Eighteen plots of 22 x 3.7 m each were separated using metal borders and the soil in six plots was mixed with sewage sludge and yard waste compost (SS-YW) at 15 t acre(- 1) on dry weight basis, six plots were mixed with sewage sludge (SS) at 15 t acre(- 1), and six unamended plots (NM) were used for comparison purposes. Plots were planted with summer squash, Cucurbita pepo as the test plant. The objectives of this investigation were to: 1) determine the dissipation and half-life (T(1/2)) of bensulide in soil under three management practices; 2) monitor the concentration of bensulide residues in runoff and infiltration water following natural rainfall; and 3) determine the effect of soil amendments on the transport of NO(3), NH(4), and P into surface and subsurface water. Half-life (T(1/2)) values of bensulide in soil were 44.3, 37.6, and 27.1 d in SS-YW, SS, and NM treatments, respectively. Addition of SS-YW and SS to native soil increased water infiltration, lowering runoff water volume and bensulide residues in runoff following natural rainfall events.