Magnesium thermophosphates from the Maicuru complex as sources of P and Mg in maize production

Termofosfatos magnesianos do complexo de Maicuru como fonte de P e Mg na produção de milho

Abstract

The objective of this work was to investigate changes in soil chemical characteristics, phosphorous concentrations in maize leaves, and the agronomic efficiency (AE) of magnesium thermophosphates produced from rocks of the Maicuru complex in the Brazilian Amazon Basin, in comparison with triple superphosphate (TSP). The thermophosphates consisted of a mixture of raw material from apatite, dunite, and quartz sandstone from Maicuru, aiming to adjust the contents of P, Mg, and Si. The mixture was melted, ground, and subjected to the analysis of solubility, chemical characteristics, and granulometry. The experiment consisted of two rates of dolomitic lime (0 and 2.4 Mg ha^-1), three rates of P (20, 60, and 100 mg kg^-1 soil), and four sources of P (TSP and three Mg thermophosphates), as well as of two control treatments, with and without lime. Three replicates were carried out per treatment in pots containing plants of the BR 5107 maize hybrid. Phosphorous concentration was determined in maize leaves at 45 days after sowing. The Mg thermophosphates showed a high AE and a higher neutralizing effect with the application of lime, which improved soil chemical characteristics and AE. The thermophosphates obtained from rocks of the Maicuru complex can be an alternative P fertilizer in maize production.

Index terms
Zea mays ; Brazilian Amazon; Oxisols; phosphate fertilizers