Supplying capacity, response to fertilization and residual effect of K fertilization were evaluated in a twelve-year soybean field experiment on a Haplohumox soil, in Campos Novos, State of Santa Catarina, Brazil. Treatments consisted of: four levels of K2O (0, 80, 160 and 320 kg ha-1), applied only in the first cropping, on the whole plots; three levels of K2O (0, 40 and 80 kg ha-1), applied annually in the sub-plots from the fifth year; one treatment with application of 40 […]

An experiment was carried out in a greenhouse, with the surface layer of a clayey Red Yellow Latosol placed in plastic pots. A 4x3x4 factorial was used. Lime rates (0; 380; 760 and 1140 mg kg-1 of soil) and potassium rates (0; 40 and 120 mg kg-1 of soil) and alfalfa cultivars (Crioula, Moapa, Florida77 and CUF101) were studied. A randomized complete block design, with four replications, was used. Plants were harvested 70 days after sowing and allowed to regrow. […]

Kinetics studies of potassium release from soils can improve our knowledge about its availability to plants. The present study, carried out in 1993, was undertaken to investigate the kinetics of potassium release and to compare four kinetics equations to describe the K-release from three soils of the State of Rio Grande do Sul, Brazil. Samples of A horizons of a Vertisol, of an Ultisol and of an Oxisol, were equilibrated with a cation exchange resin (IR-120) from one minute up […]