Fly Ash as a Source of Silicon and Potassium in Paddy Growing Soils : Status, Delineation, Release of Si & K

Rice (Oryza sativa. L) being a silicicolus plant absorbs Si in the form of mono silicic acid (H4 Si O4) through active aerobic respiration and accumulates several fold greater than those of other macronutrients from the growing medium which leads to drastic Si depletion on intensive rice cultivation. Investigations carried out in Cauvery Delta Zone revealed that 62 per cent of area is low in available Si and 30.5 percent area as low in available K . Hence there is an imperative need to utilize existing resources as the best substitute of Si. Thermal power stations in India produces large quantities of fly ash annually and its utilization is limited which is also a good source of Si and K. Hence investigations carried out using Fly Ash, silicate solubilizing bacteria (SSB) and farm yard manure (FYM) both as incubation study and field experiment in low, medium and high Si soils. Release of Si was more pronounced at 60 days after submergence. Application of graded levels of fly ash at 25 t ha-1 with 2 Kg ha-1 of SSB and 12.5 t ha-1 FYM registered the higher yield and replenished the soil Si.However the effects were more pronounced in low and medium silicon soils.