Fly Ash as a Source of Silicon for Mitigating Biotic Stress and Improving Yield and Changes in Biochemical Constituents and Silicon in Rice Under Abiotic Stress

Rice (Oryza sativa L.) is the most irreplaceable staple food for over three billion people of Asia. In Tamil Nadu, it is being grown throughout the year at different seasons under low land submerged conditions. As a result of continuous cropping, removal of silicon from soil leads to its deficiency. The rice crop shows the largest uptake of silicon playing a major role in mitigating the biotic and abiotic stresses. The fly ash is the storage of silicon in significant amount irrespective of different sources of fly ash, viz. fly ash from sugar factory, thermal power station and modern rice mill. The availability of fly ash is plenty, which poses a problem to the environment. Hence, the present study was carried out to explore the possibility of utilizing the fly ash as a source of silicon for mitigating the biotic and abiotic stress in rice. In view of the above, field experiments were conducted in low silicon soils to examine the effect of fly ash @ 25 t ha(-1) with silicate solubilizing bacteria @ 2 kg ha(-1) and farm yard manure @ 12.5 t ha(-1), with graded level of soil test-based potassium on growth and yield, incidence of pests, silicon uptake and changes in biochemical constituents, viz. total phenol, OD phenol, reducing, non-reducing sugars and proline in different plant parts such as leaf blade, leaf sheath cum stem and in ear head at different growth stages of the rice cultivar BPT 5204 under induced drought and flood conditions. The experiments were conducted at Agricultural Engineering College and Research Institute Farm, Kumulur, Trichy District, during 2012 in split plot design with two replications. The results revealed that application of fly ash with silicate solubilizing bacteria + farm yard manure with 100% soil test-based potassium increased the rice grain yield by 22 and 10.3%, under induced drought and flood stress conditions, respectively, over control. The biochemical constituents played an important role in reducing the pest incidence in induced drought and flood stress. However, the effect was more pronounced under induced drought over flood stress condition. Hence, the application of fly ash with silicate solubilizing bacteria+ farm yard manure with 100% soil test-based potassium helps to improve the growth and yield of rice. It also helps in mitigating the biotic stresses in rice by the influence of Si under induced abiotic stress, viz. drought and flood. Other biochemical constituents were also favorably correlated with the reduced incidence of pests and increased yield of both grain and straw.