Broiler litter application effects on selected trace elements under conventional and no-till systems.

摘要

This study was conducted on two separate commercial farms representing no-till at Coffeeville and conventional tillage system at Cruger in Mississippi to evaluate the dynamics of selected some trace elements in response to long-term broiler litter application to cotton. The soil at Cruger is a Dubbs silt loam (fine-silty, mixed, active, thermic Typic Hapludalfs) and at Coffeeville is an Ariel silt loam (coarse-silty, mixed, thermic Fluventic Dystrochreps). In each site, the experimental design was a randomized complete block with eight treatments replicated four times. Treatments included broiler litter rates of 0, 2.2, 4.5, and 6.7 Mg ha-1 in some combination with 0, 34, and 67 kg nitrogen ha-1. Commercial nitrogen, phosphorus, and potassium fertilizer at recommended rate was also included. At Coffeeville location at the end of third year, soil surface (0-15 cm) total C and total copper (Cu), zinc (Zn), and arsenic (As) significantly increased with increasing broiler litter applications. In Coffeeville under the no-till system, application of broiler litter at the highest rate (6.7 Mg ha-1) significantly increased soil surface (0-15 cm) total C, total Cu, Zn, and As by 28%, 67%, 51%, and 69%, respectively, as compared with unfertilized control. At Cruger location, changes in soil C and trace elements were less responsive to treatment applications. Downward movement of Cu and Zn was limited to 15 cm of soil depth, but As was detected at about 30 cm of soil depth at high broiler litter application rate. Despite elevated concentrations of trace metals at the soil surface, their concentrations in the soils were in the range considered normal with no potential threat to the ecosystems.