Subprodutos industriais como fontes de silício e condicionadores de solos tropicais em cultivo de arroz inundado

Abstract

The objective of this study was to evaluate the effect of a by-product from the phosphate fertilizer industry on chemical characteristics of tropical soils, as well as a comparison between this by-product and a by-product from the steel industry as silicon (Si) sources for flooded rice. Two experiments were carried out under greenhouse conditions at the Institute of Agricultural Science (ICIAG) at Federal University of Uberlândia (UFU), Uberlândia - MG, Brazil. In the first experiment, in addition to the phosphate fertilizer by-product, a standard source of Si (Wollastonite - CaSiO3) was used for comparison purposes. The sources were incubated for 60 days on two soil types, a Typic Dystrustox (LVd) (> 60% of clay) and a Typic Quartzipsamment (RQo) (<15% of clay) at different Si doses (0, 200, 400, and 600 kg ha-1 of Si). After the incubation period, the levels of available Si, P and Ca, pH, interchangeable Al, and P adsorption mechanisms in soils through Langmuir isotherms were evaluated. In the second experiment, AgroSiCa, Wollastonite and a by-product from the steel industry (EAA) were used. The same soils and doses of the first experiment were used, but, in this case, rice plants were grown after the incubation period. At 89 days after sowing, rice plants were harvested and dry matter (DM), Si, Ca and P levels in plants were quantified. In addition, soil samples were collected for Si, Ca and P analysis. Higher values of pH, Ca, P and Si were observed in soils under AgroSiCa application in the first experiment, as well as decreasing of Al levels and maximum phosphorus adsorption capacity (MPAC) values. It was also noted that AgroSiCa can be registered as a source of Si according to Brazilian regulations. In the second experiment, the application of both by-products resulted in increase of DM, Si, Ca, and P contents in soil samples and accumulated in rice plants. However, the by-product from the phosphate industry promoted greater nutrients accumulation in rice plants.