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.

Management of enormous amounts of crop residues generated from increased crop productivities is a serious issue and could be dealt with by composting. Understanding the effects of such compost application on soil carbon (C) and nitrogen (N) cycles is important for assessing acceptable organic sources for a particular region. We appraised the sensitivity indices and C and N pools in soils amended with full and 50% substitution of mineral fertilisers with rock phosphate enriched composts prepared from rice straw, mustard stover and tree leaves under a four-year-old wheat (Triticum aestivum)–green gram (Vigna radiata) cropping sequence in an Inceptisol. Results revealed that total organic C (TOC) increased by ~37 and 49% under tree leaf compost and tree leaf compost + 50% NPK-treated plots respectively, over unfertilised control in wheat. However, the corresponding increases were ~33 and 36% over control for green gram. The very labile C pool was more sensitive to management than TOC and less labile C. After wheat, significant improvements in total N, labile N and mineral N were found in plots receiving enriched composts applied either alone or in combination with 50% NPK. The carbon management index (CMI), nitrogen management index (NMI) and microbial C : N ratio were similar in soils amended with rice straw compost + 50% NPK, mustard stover compost + 50% NPK and tree leaves compost + 50% NPK, indicating suitability of all three organic sources in this zone. The highest values of CMI (219) and NMI (274) were maintained in mustard stover compost + 50% NPK and rice straw compost + 50% NPK-treated plots respectively. All enriched composts + 50% NPK plots had sensitivity indices (of different C and N pools) either nearer to or higher than 100% NPK plots, implying that the present integrated nutrient management with enriched composts + 50% NPK could sustain crop production and thus could be recommended.

The present study aimed to appraise the long-term effects of organics, crop residues, and biofertilisers on soil carbon (C) and nitrogen (N) pools for sustainable crop production and changes in soil quality under long-term organic farming practices. Hence, we studied the soil C and N pools and their sensitivity indices as influenced by a different combination of farmyard manure, vermicompost, biofertilisers, and crop residue of rice, wheat, and mungbean, under long-term rice–wheat–mungbean (RWMCS) and rice–wheat (RWCS) cropping systems in an Inceptisol of India. Total soil organic C increased by 78% and 104% for RWMCS and 94% and 123% for RWCS with FYM + crop residue + biofertilisers and vermicompost + crop residue + biofertilisers, respectively over unfertilised control plots of RWMCS. The highly labile C and microbial biomass C were highly sensitive to management practices compared to total organic C and less labile C fractions. Integrated application of manures and crop residues in FYM + crop residue and VC + crop residue resulted in significantly higher total N, labile N, and mineral N for both cropping systems. Higher values of C and N management indexes were observed with FYM + crop residue + biofertilisers and VC + crop residue + biofertiliser in both cropping systems than other treatments. Integrated use of organic sources had higher N fractions than the unfertilised control plots, indicating that long-term conjoint use of organics, crop residues, and biofertilisers could sustain crop production and soil quality.

The concentration of salt ions influences the availability and plant nutrients dynamics in the soil. Proper management of these ions can enhance food grain production, helping to feed the growing population. In this experiment, nine fertility combinations were followed to enhance the soil organic carbon and reduce the salt toxicity and monitor the plant nutrient availability. An incubation experiment was conducted for the period of one year with different organic soil amendments in combinations including biochar (BC), pressmud (PM), and farm yard manure (FYM) as follow: T₁-control, T₂-RDF, T₃-FYM (10 t/ha), T₄-PM (10 t/ha), T₅-BC (10 t/ha), T₆-FYM (5 t/ha) + PM (5 t/ha), T₇-FYM (5 t/ha) + BC (5 t/ha), T₈-PM (5 t/ha) + BC (5 t/ha), T₉-FYM (5 t/ha) + BC (2.5 t/ha) + PM (2.5 t/ha). Results showed that addition of organic substance (10 t/ha) significantly (p < 0.05) affected soil pH and electric conductivity. Plant nutrient availability (N, K, and S) was also influenced by application of organic substance (10 t/ha). Organic C and available N were recorded the highest in the treatment T₇ (FYM—5 t/ha + BC -5 t/ha); whereas, the highest available K and S were observed in treatment T₅ (BC-10 t/ha). The microbial soil fertility indicators (alkaline phosphatases, arylsulphatase, dehydrogenase activity and microbial biomass carbon) were measured the highest in FYM (5 t/ha) + BC (5 t/ha) applied treatment. In conclusion, application of organic substance 10 t/ha (biochar alone or with FYM) improved the plant nutrient availability and soil microbial activities in saline soil. It could be a suitable option for enhancing the soil fertility in saline soils.