Reacciones de los fosfatos monocálcico monohidratado y dicálcico anhidro en suelos volcánicos

Abstract

Reactions of monocalcium phosphate monohydrate (MCPM), ordinary superphosphate (MCP-S), and dicalcium phosphate anhydrous (DCPA) were studied in three highly P. fixing volcanic soils. Soil columns were used to reproduce the microenvironment around the fertlizer zone. The movement and reaction products of fertlizers in different soil layers in the column was determined. Among the fertilizers MCPA and MCP-S dissolved in a higher proportion as compared to DCPA. Most of the P was retained in the first layer and then it decreased exponentially. The pH of the soil in contrast with the fertilizer was decreased by MCP, although the pH was increased in the case of DCPA. The extent of P movement through the column was inversely related to allophane content. The ratio of Al-P/Fe-P decreased with increase in distance from the site of application. Liming allophanic soil up to 16 ton/ha did not show a marked increase in Ca-P. There was no marked effect of fertilizer upon occluded and reductant soluble forms of P under the present experimental conditions.