Soil organic matter and biological properties after 26 years of maize-wheat-cowpea cropping as affected by manure and fertilization in a Cambisol in semiarid region of India

Balance application of inorganic fertilizers and organic amendments greatly influence the accumulation of organic matter in soil and also the soil microbial activities. An investigation was carried out to study the changes in soil organic matter and biological properties as affected by long-term application of manure and fertilizers in maize (Zea mays)-wheat (Triticum aestivum)-cowpea (Vigna unguiculata) cropping system in a Cambisol in semi-arid region of India. The crop yield, soil organic C and total N and mineralizable C and N increased with the application of inorganic fertilizers. However, there was greater increase of these parameters when manure was applied along with inorganic fertilizers. Soil microbial biomass C was increased from 122 mg kg(-1) in unfertilized treatments to 331 mg kg(-1) in soil amended with 100% NPK + manure. The dehydrogenase, urease and alkaline phosphatase activities closely followed the soil organic carbon content and increased significantly with the addition of balanced nutrients and manure. The results indicated that soil organic matter content and soil microbial activities, vital for the nutrient turnover and long-term productivity of the soil are enhanced by balanced application of nutrients and manure. (C) 2001 Elsevier Science B.V. All rights reserved.