The traditional mode of phosphate application to cotton was compared with broadcasting application in a long term trial conducted on a DusKy Red Latosol, with a low level of phosphorus. Triple superphosphate was applied annualy (121 kg/ha of P2O5)in furrows at sowing, during six years, or broadcasted and incorporated, through one application (728kg/ha of P2O5) in the first year, or two applications in the first and fourth years (364kg/ha, at each time). A thermal phosphate (18% P2O5) was also tested in two broadcasting applications. All treatments were compared to a control, with constant doses of N and K, but without P. During the six years of phosphate fertilization, higher yields of IAC 18 cotton variety were obtained, with annual application at sowing time, except for the first year due to the low initial disponibility of P. High quantities of broadcasted phosphate led to visual potassium deficiency symptoms, with losses in yield, Micronaire index and maturity of fibers. Therefore, due to the good yield performance obtained with a moderate dose of phosphate, in the years of application, it was suggested that a combination between broadcast and localized application should be studied, in future experiments. Other characteristics of cotton such as boll and seed weight plus fiber length, also increased significantly with P fertilization. The residual effect of the traditional mode of phosphate application, studied during the last three years, with IAC 20 cotton variety, showed significant results only for yield.
phosphates; broadcast and sideband application; residual effect productivity; boll and fiber characteristics of cotton