Efeito de adubação nitrogenada, fosfatada e potássica no sorgo sacarino em um latossolo roxo

An experiment was set on a Dusky Latosol (Oxisol, clay) which presented 2.3% of OM, 4 µg/cm 3 of P and 95 µg/cm 3 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 K 2 O and 0, 100, 200 and 300 kg/ha of P 2 O 5 were applied. Maximum grain yields were associated to 114 kg/ha of N or 65, 7 kg/ha of K 2 O, 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 P 2 O 5 and 45.2 kg/ha of K 2 O 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 K 2 O.