Long-Term Leachate Water Quality Trends from a Broiler-Litter-Amended Udult in a Karst Region

Application of broiler (Gallus gallus) litter (BL) to pasturelands in karst regions like the Ozark Highlands can potentially reduce water quality due to leaching of BL-derived nutrients and trace metals. The objective of this study was to determine long-term linear trends in drainage and soil leachate water quality under natural precipitation from a silt-loam soil amended annually with BL at three application rates (0 [control], 5.6 [low], and 11.2 [high] Mg BL ha(-1)]. Automated equilibrium tension lysimeters were used to continuously monitor and collect leachate from an undisturbed soil profile with a history of litter applications under forage management at a depth of 0.9 m for the 8-yr period from May 2003 through April 2011. Average annual flow-weighted mean (FWM) concentrations and loads of NH4-N, As, Mn, and Ni decreased linearly (P < 0.05), while Cu and Se increased (P < 0.05) linearly during the 8 yr. Nearly all water quality parameters measured were unaffected (P > 0.05) by BL rate alone. Continued annual additions of BL linearly increased (P < 0.05) the average annual FWM leachate Na concentrations relative to the unamended control. Results indicated that pasturelands with a history of BL application may continue to release BL-derived metals, such as As and Se, at concentrations harmful to health regardless of current management practice long after litter application has ceased. Land application of nutrient-and trace-metal-containing animal wastes in regions with underlying karst features needs to be carefully managed to minimize subsoil leaching losses.