Effect of Integration of Flyash with Fertilizers and Organic Manures on Nutrient Availability, Yield and Nutrient Uptake of Rice in Alfisols

Field experiments were conducted for four seasons from summer 1997 to kharif 1998 at Tamil Nadu Agricultural University farm, Coimbatore on Alfisols to study the effect of longterm application of flyash alone and in combination with fertilizer, compost and Azosplrillum on yield and uptake of rice and physicochemical properties and nutrient availability of the soil. The results of the pooled mean analysis for four seasons indicated that the treatments which received flyash @ 20 and 40 t ha⁻¹ recorded a yield increase of 10.3 and 16.6 per cent, respectively over the treatments without any flyash addition. The treatments receiving N, P and K as fertilizers or fertilizers plus compost or fertilizers plus Azospirillum recorded 117, 125 and 131 per cent increase in yield over the treatments without any manurial addition. The highest yield (69.0 q ha⁻¹) was recorded when flyash applied was @ 40 t ha⁻¹ in combination with fertilizer, compost and Azospirillum. The significant increase in the uptake indicated that flyash could serve as a source of plant nutrients. Under integrated plant nutrient supply system with flyash, its effect was well pronounced. The continuous addition of lignite flyash resulted in significant increase in pH, EC, exchangeable Na, available P, K, Ca, Mg, S and Si in the post-harvest soil after fourth crop of rice. The increase in pH was not significant. The results also confirmed that even after continuous addition of flyash for three seasons, there was no hazardous level of heavy metal content that would affect soil health and crop production.