Sweet sorghum phosphate nutrition diagnosis

Abstract

Two experiments were conducted in Typic Haplorthox in the county of Jaboticabal, SP, Brazil, with the objective of determining the effects of five phosphorus levels (0, 50, 100, 200 and 400 kg/ha of P₂O₅) on ethanol and stalk yield, and furthermore, of establishing parameters for sweet sorghum phosphate nutritional diagnosis. Positive responses were obtained in stalk and ethanol (l/ha) yields due to phosphate fertilization. The samples studied can be used for the diagnosis of phosphate nutrition in the sorghum crop, given that the phosphorus contents considered to be adequate for leaves +3 or +4 are situated within the following intervals: 0.281% - 0.310% and 0.248% - 0.275%, respectively for leaves recovered during the vegetative growth stage (45 days) and flowering. On the order hand, the maxim stalk yields was associated to a soil phosphorus contents of 19 µg/cm³ (H₂SO₄ 0.05N). Reduction leaves Zn contents were observed with the highest rate of phosphorus (400 kg/ha of P₂O₅).