Technology that combines herbicide and fertilizer into one treatment thereby reducing application costs while enhancing growth is needed. Four clean and well-prepared sites in TX, MS, and AL were tested. Study objectives were to evaluate the effectiveness of diammonium phosphate (DAP) impregnated with Oust, Velpar, or Velpar+Oust for herbaceous weed control and newly planted loblolly pine (Pinus taeda L.) seedling growth. In 1999, treatments were applied early post weed-emergence to 60percent bare ground in East TX. Impregnated DAP provided about 38percent less competitor control than separate liquid and fertilizer applications at similar rates. Best seedling survival and growth resulted from liquid sprays of Oust and Velpar+Oust. Treatments in 2000 were applied to bare ground in TX, MS, and AL. Weed control for Oust-impregnated DAP, Velpar+Oust-impregnated DAP, Velpar impregnated on 250 pounds of DAP and liquid herbicide treatments was similar 120 days after treatment. Seedling survival and growth for impregnated DAP treatments was similar to that for conventional herbicide and DAP treatments. Growth trends are preliminary and will be followed. Drought probably influenced study results.
Yeiser, Jimmie L., "Weed Control and Seedling Performance Using OUST, Velpar, and Velpar+OUST Impregnated Diammonium Phosphate" (2002). Faculty Publications. 204.