Eficiência agronômica do kamafugito como fonte de fósforo e potássio para a cultura do feijão

Abstract

To increase the yield of cultivated areas in tropical soils, it is indispensable the use of large amounts of fertilizers and correctives. This increases the costs of production on farms and generates a strong dependence on imports inputs from the external market due to low domestic production. In this context, this study aimed to evaluate the agronomic efficiency and the availability of nutrients from the kamafugite rock dust in the development of bean plants. To this end, two experiments were conducted in plastic pots in the ICIAG’s greenhouse at the Federal University of Uberlândia, Umuarama campus. The first experiment was conducted in a clayey soil (Typic Dystrustox) and the second in a sandy soil (Typic Quartzipsamment), over two consecutive crop cycles. Each pot contained 5 dm3 of soil. The experimental design was a randomized complete block (RCB), with four replications, in a 4x2+4 factorial scheme, using four increasing kamafugite doses (1667, 3334, 6668, and 13336 mg dm-3), two kamafugite granulometry (filler and powder) and four additional treatments: potassium chloride (KCl = 80 mg dm-3 K2O), triple superphosphate (TSP = 252 mg dm-3 P2O5), KCl + TSP and a control treatment. Considering the acidity and the base saturation levels of each soil, doses of CaCO3 and MgCO3 were applied in all treatments in order to increase the pH level of the soils and raise their bases saturation up to 70%. The treatments were incorporated into the soils and left in incubation for 60 days before sowing. Two consecutive cultivations were carried out with the bean culture, every one lasted 42 days. At the end of each cropping, the dry matter (DM) yield of the aerial part of the plants was evaluated, as well as the pH and the contents of K, P, Ca and Mg in the soil and accumulated in the plants. Likewise, the agronomic efficiency index (AEI) of the products and the percentage of K and P recovered in the dry matter of the aerial part of the plants were evaluated. Most of the analyzed variables did not show differences between the granulometry of the kamafugite. The kamafugite promoted linear growth in almost all the analyzed variables as its doses were increased. At higher doses, the kamafugite showed comparable result to KCl. The application of the kamafugite showed greater availability of nutrients in the second crop and higher agronomic efficiency index for both forms of the product. The agronomic efficiency of the kamafugite was higher than KCl, however, lower than the TSP and KCl+TSP treatments. The kamafugite showed good residual effect for P, with higher AEI in the second cropping. The percentage of K and P recovered in the kamafugite treatment was higher than KCl in both soils, but inferior to the triple superphosphate treatments.