Efeito do superfosfato triplo (32P) na absorção do fósforo do fosfato natural pelas plantas de milho e soja / Effect of triple superphosphate (32P) on phosphate rock phosphorus uptake by maize and soybean plants

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The efficiency of phosphate rock (PR) can be improved applying it together with watersoluble P fertilizer. Four experiments were carried out in the greenhouse of the Soil Fertility Laboratory, CENA/USP (Centro de Energia Nuclear na Agricultura - Universidade de São Paulo), with maize (Zea mays L.) and soybean [Glycine max (L.) Merr.] grown in a dystrophic Typic Haplustox using 32P dilution technique to: a) verify if the increasing effect of water-soluble P source on PR phosphorus availability is physiological (initial higher P availability) or chemical (acidification), b) evaluate the effect of rate and proportion of triple superphosphate (TSP) mixed with PR, and c) compare the efficiency of Patos de Minas with of Gafsa PR applied with TSP. The P sources utilized were the TSP as standard P source and Patos de Minas and Gafsa PR. The application of a water-soluble P source improved the PR phosphorus utilization efficiency by maize and soybean, although this effect was small for the Patos PR. For maize, the simple presence of P in water-soluble form at initial stage of plant growth did not increase the PR phosphorus utilization, probably due to the short growing period in relation to soybean, in which the effect was significant. The compaction of Gafsa PR with TSP increased the absorption of PR P by maize plants. Compared to its localized application in the soil this effect was bigger in soybean plants, obtaining better efficiency than the Gafsa PR mixed in the soil. Therefore, the increased PR P utilization by soybean plants occurred by both chemical and physiological effect. The localized application of TSP promoted better results than when this fertilizer was mixed in the soil, unlike with PR. The increasing rate of P applied in mixed form (TSP and PR) did not affect the PR P utilization by the crops, while the increasing proportion of TSP in the mixture increased the absorption of PR P. The Gafsa PR, when mixed with TSP in proportion 80 TSP: 20 PR, was as efficient as the TSP applied sole.

ASSUNTO(S)

32p isotopic echnique fosfatos - tunísia phosphate fertilizers radioisótopos patos de minas phosphate rock fosfatos - patos de minas (mg) gafsa phosphate rock agronomic effectiveness soja fertilizantes fosfatados milho

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