Lime equivalence of organic manures and scope of their utilization as acid soil amendments

Abstract

ABSTRACT The effectiveness of organic manures (pig, poultry and farmyard manure, compost and vermicompost) as acid soil amendment for addressing Al toxicity and P deficiency was investigated using groundnut (cv. ICGS-76 crop) in comparison with conventional liming agent (CaCO3). The organic manures’ ash alkalinity and calcium carbonate equivalent varied from 5876 to 9506 K mol H+ kg−1 × 10−6 and 236 to 476 kg tonne−1 product, respectively. The exchangeable acidity (27.5% and 22.5%, respectively) and readily soluble Al (by 45% and 56%, respectively) in soil decreased significantly; whereas soil pH, organic carbon and microbial biomass carbon increased under the application of poultry and pig manure. In contrast to dehydrogenase and β-glucosidase enzymes, the activity of acid phosphomonoesterase in soil amended with pig and poultry manures decreased markedly. Better physicochemical and yield attributing characters (chlorophyll content, leaf thickness, cell membrane integrity, stomatal frequency, root length, root to shoot ratio, shoot dry weight, NPK uptake, pod yield and harvest index) and yield (66% and 64%, respectively) under poultry and pig manure could be related to improvement in soil fertility. Incubation study further corroborated that pig and poultry manures are the potential sources of amendments for amelioration of acid soils.