Effect of Fly Ash and Farmyard Manure on Soil Quality and Groundnut Productivity in an Acidic Soil

Fly ash (FA), an industrial by-product from coal-based power plants, remains underutilized in Indian agriculture despite its potential as a nutrient-rich soil amendment. A three-year field experiment was conducted in an acidic Inceptisol of coastal Odisha under a rice–groundnut system to evaluate the residual effects of FA in combination with farmyard manure (FYM). Treatments included graded FA doses (10, 20, and 40 t ha⁻¹) applied once to rice, with residual effects assessed in groundnut. Results demonstrated that FA application significantly improved soil organic carbon (up to 160.7%), available P (40.6%), K (49.2%), and sulphur (100.7%) relative to the control. Plant-available silicon (PASi) also increased markedly, reaching 46.98 mg kg⁻¹ in the FA40+FYM treatment. Enhanced soil enzyme activities (urease, phosphatases, dehydrogenase, β-glucosidase) indicated improved microbial functioning and nutrient cycling. Groundnut yields responded positively, with pod and kernel yields highest in the FA40+FYM treatment (1226.5 and 872.3 kg ha⁻¹, respectively), representing substantial gains over control plots. Multivariate analysis revealed strong positive correlations among soil fertility indicators, enzymatic activities, and yield attributes, with FA-amended treatments clustering distinctly from control treatments. These findings confirm that FA, when integrated with FYM and fertilizers, serves as an effective amendment for improving soil health and crop productivity in acidic soils. The study provides critical insights for sustainable FA recycling in agriculture, contributing to food security and environmental management.