Organomineral Fertilizers from Oilseed Pies

Abstract

Objective: The present study aimed to characterize oilseed cakes and phosphate sources and select promising formulations in terms of phosphorus supply.
 
 Theoretical framework: The availability of phosphates with sufficient quality for industrial processing has a reduced longevity, while materials with low phosphorus content are little used. The association between organic materials and marginal phosphorus sources has been reported as promising in the use of these materials.
 
 Methodology: Samples of castor bean (TM), crambe (TC), sunflower (TG) and jatropha (TPM), simple superphosphate (SS) and reactive natural phosphate (FNR) cakes were obtained and characterized. 48 formulations were produced, derived from a mixture of cakes, SS and FNR, in addition to isolated forms, with a nitrogen:phosphorus (N:P) ratio of 1:1 to 1:4, totaling 61 treatments. In a randomized block design, they were incubated in two soils with contrasting textures, and samples were collected at 15, 45, 75 and 105 days to determine the phosphorus content with a sodium bicarbonate solution (pH 8.5). Equations were adjusted for each formulation evaluated, and groupings were carried out to select promising mixtures.
 
 Results and conclusion: Although the cakes did not contain significant amounts, mainly of phosphorus and potassium, no toxic elements were observed, a pattern different from that observed for FNR, which contains considerable levels of cadmium. The N:P ratio 1:4 proved to be superior, providing a higher P content in the soil. Increases in P were observed in quantity and linearly throughout the evaluated period depending on the proposed mixtures in comparison to the control treatment and the application of isolated sources.
 
 Research implications: The association of nutrients from organic and mineral sources has shown promise in supplying the nutrient phosphorus, minimizing the effects of weathered soils on nutrient management.
 
 Originality/value: The study is relevant as it seeks solutions to the problem of nutritional management of tropical soils, aggravated by the high external dependence on nutrients.