Effect of Rice Husk Ash and Bagasse Ash on Inorganic Phosphorus Fractions and Available Phosphorus in an Alkaline Soil under Rice (Oryza sativa L.)-Wheat (Triticum aestivum L.) Cropping System

摘要

The cost of production of phosphatic fertilizers has increased tremendously with the rise in prices of raw materials and energy. It has been suggested that organic wastes can help to bridge the gap between demand and supply of chemical fertilizers toa great extent by supplying plant nutrients. Agro-industrial wastes like rice husk ash (RHA) and bagasse ash (BA) are available in sufficient quantities and their disposal is posing a great threat to environment causing damage to the land and the surrounding area where these are dumped. It is estimated that 45 million tonnes (Mt) of bagasse is produced annually by the sugar factories in India (NAAS 2008). The corresponding value of rice husk, which is produced as a by-product of rice mills is about 25 Mt. The BA and RHA constitute about 4.6 and 25% of the total production of bagasse and rice husk, respectively. The reaction products formed in a soil could be entirely different with chemical fertilizers than with organic ashes like RHA and BA, because of their influence on chemical reactions in soil. Fractionation of P_i, such as Ca-P, Fe- and Al-P (non-occluded Fe- and Al-bound P) can provide an effective approach for investigating soil P_i; availability and P_i inter-conversion among soil P_i fractions from different P pools (Hedley et al. 1982; Solis and Torrent 1989; Shen et al. 2004). Since there is limited information about the effect of regular applications of RHA and BA on different P fractions in soils, 3-year field study was undertaken to assess the effects of application of P through RHA and BA on the transformations of P into different inorganic (P_i) fractions and Olsen P in an alkaline soil in a rice-wheat cropping system (2006-2009). The soil of the experimental field was a Typic Ustochrept, loamy sand (5% clay and 74% sand) with pH 7.2, cation exchange capacity of 8.54 cmol(p~+)kg~(-1), EC 0.26 dS m~(-1), 3.71 g kg~(-1) organic C, 3.0 mg kg~(-1) of 0.5 M NaHCO_3-extractable P, and 55 mg kg~(-1) of 1 M NH40Ac-extractable K.