Saturday, 15 July 2006

Utilization of Solid Waste from Phosphoric Acid Industry as a Phosphorus Source to Upland Rice.

Ramegowda Suma, Chengappa Preethu, and Reddy Prabhakara. Univ of Agricultural Sciences, Dept of Soil Science and Agricultural Sciences, Gandhi Krishi Vignana Kendra, Bangalore, India

The chemical analysis of solid waste from phosphoric acid industry recorded about 8.5% of total phosphorus and appreciable amount of calcium (32%), sulfur (3.5%), iron (0.25%) and fluoride (6.86%). This solid waste was applied to rice to study its utility as source of Phosphorus (P) in terms of growth and yield of rice. The rice field was supplied with recommended dose of P through Solid Waste (WS), Single Super Phosphate (SSP), Rock Phosphate (RP) and mixture of SW+SSP (50:50 and 75:25) with or without P-Solubilizer (PS) Pseudomonas striata. Among the different P sources used, SW+SSP (50:50) with or without P-solubilizer gave higher grain and straw yield, which was on par with sole SSP application and was also beneficial in terms of economics (benefit to cost ratio). Available P in soil after harvest of rice was highest in this treatment and substantial increase in P uptake was also found. Highest F content and uptake was observed with the sole application of SW, while application of mixtures of SW + SSP significantly reduced the F content both in straw and grain. Similar trend was recorded with water soluble and total F content in soil. The higher P accumulation by rice plants resulted in lower F uptake signifying the antagonistic relationship between P and F. Significantly higher grain and straw yield of upland rice was observed with high accumulation of P. However, F activity had no toxic effect on yield.

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