Residual Soil Effects of Poultry Manures On Conventional and Conservation Tillage Fields.

Three poultry manure sources (broiler litter, BL; layer manure, LM; and composted layer manure, CLM) were applied to fields managed with conventional or conservation tillage at two sites in the North Carolina coastal plain physiographic region.  Soils were a Norfolk loamy sand (Typic Paleudults) and a Portsmouth fine sandy loam (Typic Umbraquults).  Plots were planted to a cotton-corn-cotton rotation, and received either inorganic N, poultry manure at one of two rates, or no amendment.  Initial and post-treatment soil samples documented soil pH, P, K, Cu, and Zn changes in response to poultry manure additions.  Following the first year of the study, 2008, significant amendment treatment differences were noted only for soil test K and Zn.  By the end of 2010, significant differences were noted for soil test pH, P, K, Zn, and Cu.  While soil pH declined following inorganic N addition, LM and the higher rate of CLM led to slightly higher soil pH levels than were observed without amendments.     Soil test P stratification became more pronounced over time with conservation tillage at both sites than with conventional tillage.  By 2010, ratios of soil test P in 0 to 10-cm/10 to 20-cm depth at the coastal plain site were 1.1 with conventional tillage and 1.2 with strip tillage, and at the tidewater site were 1.4 with conventional tillage and 1.5 with no-till.