EFFECTIVENESS OF ANIMAL WASTE CONTAINMENT IN A TEXAS PLAYA

Playas on the Southern High Plains are sites of active ground-water re charge to the Ogalalla aquifer and are used in agricultural and munici pal waste management systems. The effectiveness of a playa for contain ing effluent from a commercial dairy operation was studied. Four drill core holes, positioned in the annulus and alternating wet and dry zon es of a playa, provide surface and subsurface samples where dairy surf ace discharge enters the playa. Chemical and physical analyses perform ed on the core samples include nitrate-N, ammonium-N, pH, conductivity , and soil texture. Chloride distributions on two of the core profiles were compared to nitrate. Results indicate elevated nutrient levels i n the top two meters of the heavy clay floor of the alternating wet an d dry playa region, but not below that depth. A comparison of nitrate- N and chloride distribution suggests that denitrification processes pr obably eliminate most nitrate-N in this portion of the playa, This sug gests that nitrate-N, once it reaches the central region of the playa, is contained long enough to denitrify. However, movement of nitrate-N is found at the playa annulus. Another concern arises with the transp ort of chloride from the playa as indicated by its distribution below the playa center.