Five-year change in soil profile chemical properties as affected by broiler litter application rate

The broiler (Gallus gallus domesticus) industry generates large quantities of nutrient- and trace metal-enriched litter. Broiler litter (BL) is typically land applied as a nutrient source for forages. Continual annual BL applications can increase nutrient and trace metal concentrations 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 weight-based litter ha ^-1 during a 5-year period. Soil was sampled in 10-cm increments to 90 cm and characterized 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-3-extractable (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 application for 5 years in the Mehlich-3-extractable 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-3-extractable 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.