Transformation of phosphorus fractions in acid sulfate soils and their availability to rice [Oryza sativa]
1989
Nitaya Sumongkayothin
Chemical kinetics of Fe, Mn, Al in the soils were not affected by different rates of phosphate fertilizer. Bangkok and Sena soils had higher extractable Fe and Mn contents compared to Rangsit and Rangsit very acid soils. More over, Rangsit very acid soil had the highest extractable Al. Higher rates of phosphate fertilizer application resulted in higher extractable phosphate both extracted by ammonium oxalate and Bray II. The extractable Fe, Mn, Al, before transplanting and after harvesting stages were not much different in Bangkok, Rangsit very acid and Rangsit soils. In the case of Sena soil, higher content of extractable Al was obtained after harvesting stage. Extractable Fe, Mn and Al were not different at varied phosphate fertilization treatments. Extractable phosphate by ammonium oxalate and Bray II was higher with increased levels of phosphate fertilization. All 4 soils had lower recovery percentage than the results in the first experiment except the treatment T4 of Rangsit soil which had high recovery percentage. Iron phosphate is the major inorganic phosphate compound of all soils studies. Aluminum phosphate ranks the second most prevailing species in Rangsit and Rangsit very acid soils, while the same is true for calcium phosphate in Bangkok soil. Reductant soluble phosphate is the second most abundant species in Sena soil. The amount of phosphorus sorption in 4 soils also correlated to grain yield.
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