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 M. D. Meena A,B , P. K. Joshi A , B. Narjary A , P. Sheoran A , H. S. Jat A , A. R. Chinchmalatpure A , R. K. Yadav A , and D. K. Sharma A A ICAR–Central Soil Salinity Research Institute (CSSSRI), Karnal–132001, Haryana, India. B Corresponding author. Email: murliiari@gmail.com Abstract. 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. Additional keywords: composting, enzyme activity, salinity, soil fertility. Received 21 November 2015, accepted 15 February 2016, published online 29 August 2016 Introduction Improving and maintaining fertility of saline soil is vital to meeting the demands of food grain production for an increasing population in many parts of the world. In India, soils covering 6.73 Mha are salt-affected, with sodic soils comprising 3.77 Mha and saline soils 2.96 Mha (Tripathi 2011); another 16.2 Mha of land is predicted to become salt-affected by 2050 (Central Soil Salinity Research Institute 2014). Salinity has severely restricted global agriculture in arid and semi-arid regions. This stress is becoming more prevalent as land-use intensity increases throughout the world (Dong et al. 2009). Salinity inhibits plant growth through low osmotic potential of the soil solution, ion toxicity and ion imbalance, which further reduce nutrient uptake (Marschner 2012). However, inappropriate irrigation and drainage systems have resulted in rising groundwater levels, which have the potential to trigger salt accumulation in the soil profile and have a negative effect on crop production (Sharma and Minhas 2005; Qadir et al. 2009). In addition, limited precipitation, high evaporation and inadequate soil and water management have contributed to an increase in salinity. It is well known that saline soil has low fertility and biological activity. Saline soils are deficient in soil organic carbon (SOC), nitrogen (N), phosphorus (P) and potassium (K) (Lakhdar et al. 2008). In saline soil antagonism of sodium, which leads deficiency of K and calcium (Marschner 2012). Effective techniques for managing soil salinity and increasing crop productivity need to be developed. The restoration of microbial activity is a basic step in reclamation of saline soil. Application of organic amendments improves soil physical, chemical and biological properties of saline soil, and this is connected with an increase in the organic C content (Crecchio Journal compilation Ó CSIRO 2016 www.publish.csiro.au/journals/sr CSIRO PUBLISHING Soil Research, 2016, 54, 958–969 http://dx.doi.org/10.1071/SR15342