Adubação da cana-de-açúcar. X - Experiências com diversos fosfatos (1959-60)

Three experiments were conducted in 1959-60 in the State of Sao Paulo to study the efficiency of different sources of phosphorus for the production of sugar cane, using 50, 100 and 150 kilograms of total P2O5, per hectare in the presence of NK. Phosphorus significantly increased the yields in all of the experiments, in one of them, on «terra-roxa-misturada» type of soil, the natural phosphates (local rock phosphates) were statistically equivalent to the soluble phosphates (standard superphosphate, treble superphosphate and thermophosphate); however, in the other two experiments, on «terra-roxa-legitima» and «massape-salmourao» soils, the soluble phosphates showed to be significantly better. The differences between the two natural phosphates were always small; among the soluble ones they were appreciable, but not significant.