Fertilization with rock phosphate and kinetics of phosphorus uptake by soybean and cover crops of Brazilian cerrado soils Fertiliza o com fosfato natural e cinética de absor o de fósforo de soja e plantas de cobertura do cerrado

In order to identify plants with greater capacity of P uptake in Cerrado soils fertilized with phosphate rock this work was carried out with the following objectives: a) to evaluate the phosphorus (P) uptake and initial development of soybean, brachiaria, sorghum and millet in soils fertilized with soluble and rock phosphates; b) to estimate the kinetic parameters of P uptake for each species. Two experiments were conducted at Santa Catarina State University, Brazil, in the year of 2010. The first experiment consisted of plant development under the application of phosphate fertilizers to the soil. Treatments consisted of growth of four plant species (soybean, brachiaria, sorghum and millet) as affected by application of rock phosphate, triple superphosphate, and a control without P. The four replications were arranged in a 4x3 factorial using a completely randomized design. It was evaluated the plant dry matter yield and P accumulated in plant tissue. In the second experiment, we estimated the kinetic parameters of P uptake (Imax, Km and Cmín) of each species after 23 days of growth in solution culture, using a completely randomized design with four replications. Soybean did not respond to fertilization, but presents the highest dry mass yield and the greatest accumulation of P in the tissue. Triple superphosphate is the P source that caused the greatest dry matter yield for all gramineous specie. Brachiaria has a higher rate of P uptake at high concentrations of this nutrient in the solution, while the soybean has a greater capacity for P uptake at low concentrations in solution. A fim de identificar plantas com maior capacidade de absor o de P em solos de cerrado adubados com fosfato natural, visando à ciclagem deste nutriente, objetivou-se: a) avaliar a capacidade de absor o de fósforo e o desenvolvimento inicial de soja, sorgo, milheto e braquiária em fun o da aplica o de fosfato solúvel e natural ao solo; b) estimar os parametros cinéticos de absor o de P dessas espécies cultivadas em solu o nutritiva. Para tanto, foram realizados dois experimentos no Centro de Ciências Agroveterinárias da Universidade do Estado de Santa Catarina (CAV/UDESC), no ano de 2010. O primeiro experimento constou do desenvolvimento de plantas (soja, braquiária, sorgo e milheto) em solos adubados com fosfato natural e superfosfato triplo, além de um tratamento sem aplica o de P, arranjados em um fatorial 4x3, sob delineamento inteiramente casualizado, com quatro repeti es. Foram avaliadas a produ o de massa seca das plantas e a quantidade de P acumulada no tecido.