Long-term Effects of Broiler Litter Application Rate on Runoff, Leaching, and Soil Respiration from a Captina Silt Loam

Producers in regions with intense broiler (Gallus gallus) production take advantage of the plant nutrients contained in broiler litter (BL) to enhance yields of forage grasses. However, application of BL to pasture lands in karst regions, like the Ozark Highlands, can potentially reduce water quality if BL-derived contaminants enter surface or groundwater via runoff or drainage. Additionally, BL applications stimulate carbon dioxide (CO2) release from the soil to the atmosphere and may contribute to global warming. The objectives of this study were to determine long-term trends in runoff and soil leachate water quality and to evaluate soil respiration under natural precipitation from a Captina siltloam soil (fine-silty, siliceous, active, mesic Typic Fragiudult) with a history of BL amendments under forage management amended annually with BL at three application rates (0, 5.6, and 11.2 Mg BL ha-1). Runoff and leachate were collected for an 8-yr period and pH, electrical conductivity (EC), soluble plant nutrients (i.e., NO3-N, NH4-N, PO4-P, Ca, K, Mg, Na, and P), trace metals (i.e., As, Cd, Cr, Cu, Fe, Mn, Ni, Se, and Zn), and dissolved organic carbon were measured. Similarly, soil respiration, temperature, and moisture were measured periodically for a 3-yr period. Litter application increased (P < 0.01) average annual flow-weighted-mean (FWM) runoff Fe and leachate Na concentrations, while all other annual runoff and leachate concentrations and loads and 8-yr cumulative losses were unaffected (P > 0.05) by BL rate. Eight-year cumulative runoff losses were < 1 % for all elements except Se, which ranged from 12 to 20 % of that applied in litter. Similarly, 8-year cumulative leaching losses of NH4-N, C, N, P, Mn, and Cu represented < 2%, while Se and Cd exceeded 100% of that applied in BL. Soil respiration varied (P < 0.01) with BL rate, sample date, and year. Litter increased respiration after application and again after rain events relative to the unamended control in all years. Multiple regression indicated that respiration could be predicted using soil temperature at the 2-cm depth (T2cm) and the product of T2cm and soil volumetric water content (R2 = 0.52; P < 0.01). Results indicate that pasturelands with a history of BL application may release BL-derived metals in runoff and drainage waters at concentrations harmful to health and that organic amendments, such as BL, can stimulate net release of CO2 from soil to the atmosphere, potentially negatively affecting atmospheric greenhouse gas concentrations. Acknowledgments The author wishes to place on record an expression of his appreciation for the help and generous treatment he received from the kind Faculty and Staff of the Crop, Soil, and Environmental Sciences Department and from his colleagues in the Soil Physics Laboratory. The author wishes to thank the members of his Advisory/Dissertation Committee, Professors K.R. Brye, E.E. Gbur, D.M. Miller, R.E. Mason, M.A. Evans-White, and S.E. Watkins for undertaking the responsibility of planning the author’s course work, guiding him in his research, and supervising the preparation of this dissertation. The author would like to thank Professor K.R. Brye for serving as his major advisor as well as being the Chairman of his committee. Professor Brye’s devotion to the review process was instrumental in the preparation of this dissertation. The author would like to thank Professor D.M. Miller for his previous guidance during the author’s earlier graduate endeavors. Without Professor Miller’s encouragement to return to academia, the author would not have attained this level of achievement. The author wishes to thank Professor E.E. Gbur for his willingness to discuss statistics as it pertained to the current body of work. Professor Gbur’s guidance was reassuring. The author would be guilty of a serious omission if he failed to make special mention of the gratitude he owes to the former graduate students. The devotion of time and effort exhibited by Amanda L. Pirani, Brie C. Menjoulet, and Aaron L. Daigh to collect runoff and drainage after every rainfall event for an extended period of time cannot be surpassed. The author is grateful to Professor H.D. Scott for introducing him to the world of soil science in general and soil physics in particular. Without the initial contact that the author experienced in Professor Scott’s laboratory so many years ago, the author’s love of soil may not have blossomed. The author recognizes Col. William A. Myers and Dean Patricia R. Koski as two great leaders and communicators. Character traits of such individuals are considered templates for the author’s own personal development. The author would like to thank Sharon Faye Smith and Kirk Deffenbaugh for their friendship. Companionship like yours is hard to come by. The author would like to thank his children and wife. Without their generous sacrifices and patience, this work could not have been completed. For the commitment, encouragement, inspiration, and support from the author’s wife, the author owes a lifetime of gratitude. I’m sorry for all the missed rollercoaster rides. To Alexandria, Isaac, and Valerie Table of