Liming potential of poultry litter in a long-term tillage comparison study

Abstract Soil acidity is a constraint to global soil and food security, yet access to limestone to correct this problem is limited in many parts of the world. Research suggests that animal manures have a liming effect on acidified soils, representing a potential solution. This long-term (15 year) study used a split plot design to evaluate the effect of conventional tillage (CT) vs no-till (NT) (main plot) under conventional (CF) and poultry litter (PL) fertilizer source applications (sub-plots). A succession of three cropping systems consisting of cotton (Gossypium hirsutum L.) with a winter wheat (Triticum aestivum) cover crop, corn (Zea mays) with rye (Secale cereal), and millet (Panicum miliaceum) with rye was implemented. The soil is a Cecil sandy loam (1:1 kaolinitic). Changes in soil pH, soil organic carbon (SOC), and lime buffer capacity (LBC) were compared among the four treatments CTCF, CTPL, NTCF, and NTPL. The CTPL treatment had a 0.6 unit pH increase in the top 15 cm. However, cropping systems had more effect than tillage or fertilizer source on both soil pH and LBC. All treatments resulted in some increase in subsoil pH. Lime buffer capacity remained unchanged at all but the 76–91 cm depth, where all treatments exhibited a decrease ranging from 27 to 43 kg CaCO3 eq ha−1 pH unit−1 year−1. Our results suggest that previously reported liming effect of animal manures should be examined in the context of soil type and cropping system to better understand the true mechanism(s) of soil acidity amelioration.