Effects of municipal solid waste compost, rice-straw compost and mineral fertilisers on biological and chemical properties of a saline soil and yields in a mustard-pearl millet cropping system

We investigated the effects of organic amendments, municipal solid waste compost (MSWC) and rice-straw compost (RSC) with and without mineral fertilisers on biological and chemical properties of a saline soil. Field experiments were conducted for two consecutive years during 2012-14. In the first year, application of 8 t ha(-1) of MSWC + 50% of the recommended dose of fertilisers (RDF) resulted in higher microbial biomass carbon (MBC), enzyme activities, soil organic carbon (SOC), available nitrogen (N), phosphorus (P) and potassium (K) than 7 t ha(-1) of RSC + 50% RDF, after mustard (Brassica juncea) and pearl millet (Pennisetum glaucum) harvests. Combined use of 8 t ha(-1) of MSWC+ 50% RDF resulted in 47% and 54% more MBC than the unfertilised control after mustard and pearl millet harvests, respectively. Dehydrogenase activity was significantly higher with 100% RDF than the control after 2 years of the cropping cycle. Among organic amendments, MSWC was superior to RSC in terms of MBC, and activities of dehydrogenase, alkaline phosphatase and urease. SOC was significantly increased under MSWC+ 50% RDF compared with 100% RDF alone. Significant build-up of soil fertility in terms of available N, P and K was observed with RSC + 50% RDF compared with the control. During the second year of the cropping system, soil treated with RSC + 50% RDF had 14%, 17% and 9% higher N, P and K than soil treated with 100% RDF, after pearl millet harvest. The magnitude of change in soil electrical conductivity and pH was low during 2012-13; however, soil salinity decreased by 55% and 48% with MSWC+ 50% RDF and RSC + 50% RDF, respectively, relative to the control at 120 days of pearl millet growth in 2013-14. Application of MSWC + 50% RDF produced 2.5 and 2.70 t ha(-1) of mustard and pearl millet, and increased grain yield by 19% and 15%, respectively, compared with 100% RDF. Integrated use organic amendments and mineral fertiliser is recommended for promoting biological and chemical properties of saline soil in a mustard-pearl millet cropping system.