Rationalizing mineral gypsum use through microbially enriched municipal solid waste compost for amelioration and regaining productivity potential of degraded alkali soils

Abstract

Reclamation of alkali soils to harness their productivity potential is more complex due to the presence of excess sodium ions, poor hydraulic conductivity and infiltration rate, resulting in poor plant growth and crop productivity. Sodic soil reclamation using inorganic ameliorants like mineral gypsum or phosphogypsum is beyond the reach of small and marginal farmers having alkali soils because of their higher market prices and shortage of availability. Conjoint use of inorganic and organic amendments can be a pragmatic solution for improving soil physico-chemical and biological properties and sustaining crop productivity. Municipal solid waste compost (MSWC) available in abundant quantity if enriched with the efficient halophilic microbial consortium and used in conjunction with a reduced dose of gypsum can be a cost-effective approach for sustainable reclamation of alkali soils and harnessing their productivity potential. Hence, a field experiment was conducted on a high alkali soil (pH₂ 9.2 ± 0.10), electrical conductivity (EC) 1.14 ±  0.12 dS m⁻¹, exchangeable sodium percentage 48 ± 2.50 and organic carbon (0.30%) was conducted during 2018–19 to 2020–21 to study the combined effect inorganic and organic (enriched municipal solid waste compost (EMSWC)) amendments on amelioration of alkali soils and sustaining productivity of rice–wheat cropping system. Application of gypsum @ 25% GR + enriched MSW compost @ 10 t ha⁻¹ (T₆) showed significant improvement in soil physico-chemical and biological properties over the sole application of organic (T₃ and T₄), inorganic (T₂) and control (T₁). A significant improvement in soil fertility status in terms of available nitrogen and micronutrients as well as CO_3, HCO₃, Cl, Ca and Mg content were recorded with the combined application of organic and inorganic soil amendments (T₅ and T₆) over the sole application of mineral gypsum. Soil microbial biomass carbon (MBC), nitrogen (MBN) and phosphorus (MBP) improved significantly due to the application of EMSWC with gypsum over the application of gypsum only. Grain yield of rice and wheat increased significantly (P < 0.05) owing to the application of a reduced dose of gypsum (25% GR) and EMSWC @ 10 t ha⁻¹ (T₆) with values of 5.55 and 3.83 t ha⁻¹, respectively over rest of the treatments. Three years economic analysis of the study revealed that treatments T₆ and T₅ gave the highest positive net return whereas it was lowest in treatment T₁ and negative in treatment T₂. The highest benefit-to-cost ratio (B:C) was obtained in treatments T₆ and T₅ which were significantly higher compared to the rest of the treatments.