Estudo da utilização de pó de rocha diorítica como recondicionador de solo agrícola do município de Crateús

Abstract

Given the problem of agricultural soils with deficiencies in inorganic nutrients, the dependence on imports of chemical fertilizers, the economic constraints of producers in acquiring these fertilizers, and their environmental impact, the alternative of using rock dust as a source of inorganic fertilization is sought. This option is regional, accessible, and sustainable. However, the use of rock dust requires more time for nutrient release compared to conventional fertilizers. In an attempt to contribute to solving the mentioned problem and focusing on accelerating nutrient release, this study aimed to analyze, at a laboratory scale, the application of natural rock dust with thermal and thermal/chemical treatment in agricultural soil with bean cultivation. Initially, rocks and soils were collected in the municipality of Crateús, followed by their characterization. Subsequently, the rock was crushed and ground, with a fraction subjected to thermal treatment, reaching an average temperature of 290°C, and a portion of this fraction underwent chemical treatment with acetic acid. The experiments were conducted in duplicates, placed in 300 mL disposable cups, and 130 grams of soil were used in all tests. Initially, natural rock dust, thermal rock dust, and thermal/chemical rock dust were used in concentrations of 200, 100, and 50 grams. NPK and ammonium sulfate were also used in concentrations of 50, 25, and 5 grams, and 65, 32.5, and 13 grams of limestone, to compare the results of rock dust with chemical products. In total, 39 experiments were conducted, each watered with 50 mL of water daily during the experiments. During the development period, the weight and height of the seedlings were measured every three days. According to the characterization tests, the collected rock was classified as diorite, and the granulometry of the used rock dust was 81% passing through a 0.6 mm sieve. Regarding the analysis of seedling development, the weight data were discarded due to inconsistencies, and the height data were statistically analyzed with IBM SPSS software. Data analysis showed that treatments using NPK and ammonium sulfate did not show responses, and the treatment with agricultural limestone showed discrepancies in the experiments, so both were discarded. Treatments with rock dust showed good responses, with the 200g natural rock dust having the best final plant growth response, and the thermal and thermal/chemical rock dusts showing good responses in smaller dosages. The 50g thermal dust appears to be the most advantageous in terms of growth per amount of material used. The chemical treatment negatively affects the thermal treatment. Therefore, it was noted that rock dust contributes to final growth and growth rate, with thermal treatment helping reduce rock dust consumption for small dosages.