Five-Year Change in Soil Profile Chemical Properties as Affected by Broiler Litter Application Rate Aaron L. Daigh, 1 Kristofor R. Brye, 1 Andrew N. Sharpley, 1 David M. Miller, 1 Charles P. West, 1 and Van J. Brahana 2 Abstract: The broiler (Gallus gallus domesticus) industry generates large quantities of nutrient- and trace metalYenriched litter. Broiler litter (BL) is typically land applied as a nutrient source for forages. Continual annual BL applications can increase nutrient and trace metal concentra- tions in soil over time, creating the potential for negative environmental impacts. The objective of this study was to determine the long-term effects of BL application rate on soil profile chemical properties in a Captina silt loam (fine-silty, siliceous, active, mesic, Typic Fragiudult) with a history of BL applications. Broiler litter was applied annually at 0, 5.6, and 11.2 Mg of dry weightYbased litter ha j1 during a 5-year period. Soil was sampled in 10-cm increments to 90 cm and charac- terized for pH, electrical conductivity, organic matter, dissolved organic C, P saturation, and acid-recoverable (P, K, Ca, Mg, S, Na, Fe, Mn, Zn, Cu, Al, As, Cd, Cr, and Se), Mehlich-3Yextractable (P, K, Ca, Mg, Na, Fe, Mn, Zn, and Cu), and water-soluble (P, K, Ca, Mg, S, Na, Fe, Mn, Zn, Cu, Al, As, Cd, Cr, and Se) soil nutrient and trace metals. Soil nutrient and trace metal contents generally increased with continued BL ap- plication for 5 years in the Mehlich-3Yextractable and water-soluble pools. Soil properties affected by litter treatment generally increased over time in the top 20 cm as litter rate increased. It seems that continued annual application of BL to soil with a history of BL application will continue to accumulate Mehlich-3Yextractable and water-soluble soil nutrient and trace metals near the soil surface. A decrease in soil nutrient and trace metal contents when BL applications ceased generally did not occur. Therefore, it seems that decreases in most soil chemical property magnitudes caused by the cessation of BL applications will require more than 5 years and could continue to pose potential negative environmental consequences. Key words: Soil chemical properties, broiler litter, application rate (Soil Sci 2009;174: 531Y542) T he broiler (Gallus gallus domesticus) industry generates large quantities of nutrient- and trace metalYenriched litter, particularly where production is highly concentrated. The United States produces approximately 9 billion broilers annually (USDA-NASS, 2006), generating between 9 and 13.5 million Mg of litter (UA-CES, 2006) that is composed of bedding material, typically pine (Pinus species) shavings or rice (Oryza sativa L.) hulls, feed, and raw manure. Broiler litter (BL) is typically applied to pasturelands as a nutrient, primarily N, source for forages (Edwards and Daniel, 1992). Regions with concentrated broiler production typically have nearby pasture- lands that have received decades of annual BL applications. In addition to N, BL contains numerous other plant nutri- ents and trace elements, such as P, K, Ca, Mg, S, Cu, Fe, Mn, Na, Zn, Al, As, Cd, Cr, and Se, contained in feed additives supplied in the broilers’diet (Tufft and Nockels, 1991; Sims and Wolf, 1994; Sims, 1995; Han et al., 2000). Long-term annual BL ap- plications can increase nutrient and metal concentrations in soils (Gupta and Charles, 1999; Han et al., 2000; Kpomblekou-A et al., 2002), which could result in potential negative environ- mental impacts. Once BL is land applied, the litter’s constituents can un- dergo numerous environmental fates, including runoff, plant uptake, leaching, and soil storage. Storage of nutrients and trace metals in soils from BL applications may initially be of minor environmental concern compared with that of other potential fates. However, the magnitude of acid-recoverable, Mehlich- 3Yextractable, and water-soluble pools and the possible changes over time of soil chemical properties caused by repeated annual BL applications may influence the other fates and lead to poten- tial negative impacts on local plant and water resources. The accumulation of nutrients and trace metals in soil caused by the addition of organic amendments has been studied primarily in soil surface horizons or within the upper part of the root zone. Sharpley et al. (1993) reported that soil P concentra- tions were greatest in the top 5 cm and concentrations decreased with depth in soil with Bermudagrass (Cynodon dactylon [L.] Pers.) vegetation that had been amended with an average of 6 Mg litter ha j1 annually for 35 years. In addition, soil P accu- mulation tended to be limited to the top 30 cm (Sharpley et al., 1993); however, Kingery et al. (1994) observed soil P enrich- ment to nearly 60 cm. Approximately 72% of the total P in BL is retained in soil, whereas Bray-1Yextractable soil P increased 22 mg P kg j1 soil per 100 kg P ha j1 applied as BL (Sharpley et al., 1993). Mitchell and Tu (2006) showed Mehlich-1Y extractable P accumulations from 25 to 125 mg P kg j1 soil for 9 years on a fine-sandy-loam Ultisol and accumulations from 18 to 64 mg P kg j1 soil for 3 years on a silt-loam Ultisol, in which both had 9 Mg BL ha j1 year j1 applied to a cotton (Gossypium hirsutum L.)-corn (Zea mays L.) rotation. Gupta and Charles (1999) observed significant accumulation of As, Cd, Cu, and Mn in the top 20 cm of a sandy-clay-loam soil after 20 years of corn production and litter applications of 9 Mg ha j1 every 2 years. Han et al. (2000) reported Cu, Zn, and Mn accu- mulations in the top 20 cm of soil after 25 years of applications of 10 to 30 Mg litter ha j1 year j1 to Bermudagrass pastures. However, because soil is inherently spatially variable, the ability of soil to retain nutrients and trace metals is also spatially vari- able (Liang et al., 1990). Accumulation of excess nutrients and trace metals in the environment may produce increased algal growth in water sys- tems and bioaccumulation and toxicity within plants or animals (Hu et al., 2007; Rogival et al., 2007). The environmental risk is of greatest concern with nutrients and trace metals that are capable of being transported by leaching and runoff into nearby surface or groundwater. Nutrient and trace metals that can accumulate in soil below the root zone may be rendered immobile by various soil TECHNICAL ARTICLE Soil Science & Volume 174, Number 10, October 2009 www.soilsci.com 531 1 Department of Crop, Soil, and Environmental Sciences, University of Arkansas, 115 Plant Sciences Bldg., Fayetteville, AR 72701. Mr. Daigh is corresponding author. E-mail: adaigh@yahoo.com 2 Department of Geosciences, University of Arkansas, Fayetteville, AR. Received May 26, 2009. Accepted for publication August 20, 2009. Copyright * 2009 by Lippincott Williams & Wilkins, Inc. ISSN: 0038-075X DOI: 10.1097/SS.0b013e3181bdbdb3 9 Copyright @ 200 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.