Impact of fly ash and farmyard manure on one health continuum of soil, grain and environment in maize

Fly-ash (FA) is a valuable coal combustion residue with enormous potential to use in agriculture but dose optimisation is a must. The objectives of the present field study (started in 2021; completed 2 crop cycle) was to assess the impact of 12 diverse FA-doses applied annually (10, 20 and 40 t ha − 1 ), biannually (20, 40 and 80 t ha − 1 ) and once (100, 200 and 400 t ha − 1 ) on changes in soil quality, emissions of greenhouse gases (GHGs) and bio-chemical characteristics of maize grains. Conceptual frame work based soil quality index (CFSQI) was developed under both productivity (P) and environmental protection (EP) management goals. Recommended dose of fertiliser (RDF) along with and farm yard manure (FYM) (RDF + FYM) showed the highest CFSQI-P (0.78) and CFSQI-EP (0.71) in 0–15 cm soil depth. The cumulative emissions of nitrous oxide (N 2 O) and ammonia (NH 3 ) was highest in RDF + FYM (1.49 kg N 2 O ha − 1 ) and RDF + FYM+FA-alternate year (AY) 80 t ha − 1 (36.41 mg kg − 1 ), respectively. The Mg and Cu content in maize grain increased significantly with increase in FA dose, while the Cd and Pb contents did not exceed the permissible limits of these metals. The anti-oxidant activity (47.51 µmoltrolox g − 1 ) and total phenol (53.63 mg 100 g − 1 ) contents in grains was recorded highest in annual application of FA at 20 and 40 t ha − 1 along with RDF + FYM, respectively. The rank analysis suggested based on all (soil properties, GHG emission and grain attributes) traits revealed that application of FA (annually 10 t ha − 1 ) along with RDF + FYM scored highest (0.789) with first rank. Thus, based on the experimental findings, it could be concluded that the application of FA (10 t ha − 1 ) along with integrated fertiliser management emerged as a strategy under maize-wheat system which could improve soil quality, mitigate gaseous emissions and sustain maize grain quality with possible no inimical impacts on animal and human health.