Effects of nitrogen, phosphorus and potassium fertilization on sweet Sorghum grown on a dusky latosol

Abstract

An experiment was set on a Dusky Latosol (Oxisol, clay) which presented 2.3% of OM, 4 µg/cm³ of P and 95 µg/cm³ of K, to study the effects of nitrogen (Ammonium Sulphate), phosphorus (simple superphosphate) and potassium (potassium chloride) fertilization on sweet sorghum (Sorghum bicolor (L.) Moench, cv. Brandes) grain and stalk yields. Levels of 0, 60, 120 and 180 kg/ha of N and K₂O and 0, 100, 200 and 300 kg/ha of P₂O₅ were applied. Maximum grain yields were associated to 114 kg/ha of N or 65, 7 kg/ha of K₂O, but there was no response to phosphate fertilization. There was a increase in stalk yield only due to N fertilization up to 77, 5 kg/ha. Nitrogen, phosphorus and potassium levels in the leaves, of 2, 25%, 0, 18% and 1,50%, respectively, were associated to high yields both for grains and stalks. There was not any effect of fertilizer treatments upon juice quality. For grain production, the levels of 74.1 kg/ha of N, 0 kg/ha of P₂O₅ and 45.2 kg/ha of K₂O would be most economical, while only 34.9 kg/ha of N are economically recommended for stalk yield improvement. If both stalk and grain yields are considered, the must economical levels would be 76 and 34 kg/ha of K₂O.