Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 6, 2007
Publication Date: June 1, 2007
Citation: Adeli, A., Sistani, K.R., Tewolde, H., Rowe, D.E. 2007. Broiler litter application effects on selected trace elements under conventional and no-till systems. Soil Science. 172:349-365. Interpretive Summary: Understanding the dynamic of trace elements applied by broiler litter application to the row crops under different soil management practices is important in developing a sustainable agricultural production system. Broiler litter, on average, contains considerable amounts of trace elements including Cu, Mn, Zn, As (390, 655, 377, 38 mg kg-1, respectively), which may vary depending on broiler production and management practices. Several trace elements such as As, Cu, Fe, Mn, Se, and Zn are important components in broiler rations and they are added into feeds to ensure an optimal supply for weight gain and to minimize health disorders and avoid diseases. Repeated application of broiler litter with significant concentration of trace elements may result in accumulation of trace elements into the soil surface that might become toxic to plants, animals, and humans or may enter water systems through surface runoff and leaching. Although generally assumed that poultry litter rarely contains high concentrations of potentially harmful metals such Mn, Cu, and Zn, long-term repeated application of poultry litter as a sole source of fertilizer can cause their accumulation in top soils near phytotoxic levels. The low trace metal requirement by crops is an important reason for their accumulation. Little is known about the soil accumulation of trace elements such as Cu, Zn, and Mn in response to broiler litter application to row crops such as cotton under different soil management systems. Since the efficiency of cotton in extracting litter-derived metal nutrients has not been documented in the field, quantification and the mobility of these trace elements from broiler litter application to cotton in soils under different soil management systems is needed to minimize metal accumulation and transformation and keep the soil metal concentration to near phytotoxic levels.
Technical Abstract: A study was conducted for three years on two separate commercial farms representing no-till and conventional tillage practices. The experimental design was a randomized complete block with 5 treatments replicated four times. Treatments included four broiler litter application rates to cotton at 0, 2.2, 4.5, and 6.7 Mg ha-1 and a fertilized farmer standard. At the end of the third year, especially at the 0-15 cm depth, soil total C (TC), Mehlich 3 extractable copper (Cu), zinc (Zn), manganese (Mn) and arsenic (As) increased with increasing broiler litter application rates. Averaged across broiler litter rates, their concentrations were 13%, 34%, 30%, 71% and 20% greater in no-till than in conventional tillage system, respectively. Downward movement of Cu, Zn was limited to 15 cm soil depth but as movement was detected to about 30 cm soil depth, whereas Mehlich 3 extractable Mn was not affected by the soil depth. In this study, despite elevated concentrations of trace metals at the soil surface, their concentrations were in the range considered normal in soil. However due to the very low cotton trace metal requirement, long-term continued application even at sustained rates to supply required N may result in trace element accumulation over years especially in a no-till system and carries the potential risk from unacceptable soil trace metal concentrations.