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.

Repeated annual land application of organic soil amendments, such as broiler litter (BL), to managed grasslands for increased forage yields has increased concerns about potential surface water contamination from runoff. Furthermore, water quality concerns are exacerbated in areas of underlying karst, such as the Ozark Highlands, where runoff can rapidly enter the groundwater system. Therefore, the objective of this study was to determine 8‐yr (May 2003–April 2011) linear trends in annual runoff water quality from a silt loam soil in the Ozark Highlands region of northwest Arkansas under natural precipitation and typical forage management amended annually with BL at three application rates (0 [control], 5.6 [low], and 11.2 [high] Mg BL ha−1) with a history of BL amendments and high soil‐test P. Average annual runoff, flow‐weighted mean (FWM) runoff concentrations of Ca, Cd, Cu, Na, and Se, and all nutrient and metal losses increased with time (P < 0.05) but were unaffected (P > 0.05) by BL application rate. Average annual FWM concentrations of As decreased with time (P < 0.05) and were unaffected by BL (P > 0.05). Eight‐year cumulative runoff losses of Se exceeded 200% of that applied in BL. Results indicated that pasturelands with a history of BL application and high soil‐test P may continue to release BL‐derived As and Se at concentrations potentially harmful to human and environmental health regardless of current management practice long after litter application has ceased.

No abstract

The United States produced 8.4 billion broiler chickens () and an estimated 10.1 to 14.3 million Mg of broiler litter (BL) in 2012. Arkansas' production of 1 billion broilers in 2012 produced an estimated 1.2 to 1.7 million Mg of BL, most of which was concentrated in the Ozark Highlands region of northwest Arkansas. Increased CO release from soils associated with agricultural practices has generated concerns regarding the contribution of certain agricultural management practices to global warming. The objectives of this study were to evaluate the effects of long-term (>6 yr) BL application to a Udult on soil respiration and annual C emissions and to determine the predictability of soil respiration based on soil temperature and moisture in the Ozark Highlands region of northwest Arkansas. Soil respiration was measured routinely between May 2009 and May 2012 in response to annual BL application rates of 0, 5.6, and 11.2 Mg dry litter ha that began in 2003. Soil respiration varied ( < 0.01) with BL rate, measurement date, and year. Additions of BL stimulated respiration after application, and rainfall events after dry-soil conditions stimulated respiration in all years. Soil temperature at the 10-cm depth, 0- to 6-cm soil volumetric water content (VWC), and annual CO-C emissions were unaffected ( > 0.05) by BL application rate but differed ( < 0.01) among study years. Multiple regression indicated that soil respiration could be reasonably predicted using 2-cm-depth soil temperature (T) and the product of T and VWC as predictors ( = 0.52; < 0.01). Results indicate that organic amendments, such as BL, can stimulate release of CO from the soil to the atmosphere, potentially negatively affecting atmospheric greenhouse gas concentrations; thus, there may be application rates above which the benefits of organic amendments may be diminished by adverse environmental effects. Improved BL management strategies are needed to lessen the loss of CO from BL-amended soils.

In regions with concentrated broiler (Gallus gallus) production, land application is a useful means of managing broiler litter (BL). However, surface and subsurface water quality issues may arise when continued annual BL application to fields occurs for extended periods. The application of manure follows seasonal guidelines for surface water quality protection. The objective of this study was to evaluate the effects of BL rate (0, 5.6, and 11.2 Mg litter ha −1 ) and season on drainage and leachate water quality over an 8-yr period (2003-2011) in the Ozark Highlands with karst geology using automated, equilibrium-tension lysimeters. During the 8-yr period, seasonal drainage was unaffected by season or BL rate, averaging 118 mm per season. Averaged across BL rates, seasonal leachate pH, electrical conductivity (EC), flow-weighted mean (FWM) NO 3 -N, dissolved organic C, S, and Zn concentrations, and NH 4 -N, Cu, Fe, and Se loads differed (P < 0.05) among seasons. Averaged across seasons, seasonal leachate EC, FWM PO 4 -P, total P, and S concentrations, and Ni load differed (P < 0.05) among BL rates. With the exception of As and Se, seasonal FWM leachate Cd, Cr, Cu, and NO 3 -N concentrations were at least five times smaller than their maximum contaminant level for drinking water during any of the four seasons. Since rainfall patterns seasonally change in many regions of concentrated poultry production, seasonal differences in the leachate water quality response to continuous annual application of BL are important to help tailor best management practices to protect soil and water resources in regions underlain by karst geology. Abbreviations: BL, broiler litter; DOC, dissolved organic carbon; EC, electrical conductivity; FWM, flow-weighted mean. Citation: Brye, K.R., A.L.M. Daigh, and R.L. McMullen. 2018. Seasonal effects on leachate quality from an Ozark Highlands managed grassland using automated, equilibrium-tension lysimeters. Vadose Zone J. 17:160082.