N and P Release Pattern in Saline-sodic Soil Amended with Gypsum and Municipal Solid Waste Compost

Abstract

Nitrogen and phosphorus are the major nutrients limiting crop production in saline-sodic soils. The reclamation and nutrient supplying potential of municipal solid waste compost (MSWC) from Karnal and Delhi was studied in saline-sodic soil (with pH1:2 10.16; electrical conductivity (EC1:2)3.09 dSm-1;exchangeable sodium percentage 77.5) with conjunctive application of gypsum (25% recommended doses of mineral gypsum, GR25) and 10 Mg ha-1 MSWC at 60% water holding capacity for three months. Soil showed alkaline reaction for the whole incubation period. The combined application of GR25 and compost KC and DC are equally effective compared with GR50 on declining soil pH1:2. Amended soils upon incubation showed a decrement in aqueous extractable Ca2+ while increase in K+ and HCO3- and CO32- concentration in soil solution. During incubation, N and P were initially immobilized and after reaching the maxima of immobilization, these entered in mineralization phase. Application of gypsum (GR50 and GR25) caused overall deficit of the N compared to control. Integration of MSWC with gypsum resulted in increased N content in soil system. Both the composts showed similar values of N at different days of incubation. Gypsum caused decline in soil P. MSWC compensated for gypsum induced deficit, and available P of Karnal (30.7 mg kg-1) and Delhi (29.3 mg kg-1) were at par with control (32.0 mg kg-1). Therefore, this study recommended that application of 10 Mg ha-1 municipal solid waste compost with gypsum 25GR can reduce soil pH and efficiently supply N and P compared to sole gypsum application.