Abstract

Nitrogen, phosphorus and potassium are nutrients that are directly involved in the entire life cycle of plants. Wood ash is solid with high or low concentrations of phosphorus and potassium depending on the material of vegetable origin. The objective of the present study was to evaluate the concentrations of nitrogen, phosphorus and potassium in tropical grasses in 2 cultivars of Brachiaria brizantha resulting from differing doses of wood ash. Completely randomised design in a 6x2 factorial with 6 doses of vegetable ash (0; 3; 6, 9; 12 and 15 g dm^-3) and 2 cultivars of B. brizantha (Marandu and Xaraes) with 6 replications. In the first cut, the nitrogen concentration in the shoots of Marandu grass increased by 65.13%, and the potassium concentration increased by 36.12 and 42.37% in the Marandu and Xaraes grasses, respectively. In the third section, the phosphorus concentration in the shoots of both grasses increased 38.78%. In the roots of the Marandu and Xaraes grasses, the concentrations of phosphorus and potassium increase by 25.17 and 35.93%, respectively. The wood ash as fertiliser improves the concentrations of nitrogen, phosphorus and potassium in the shoots and roots of the tropical grasses Marandu and Xaraes.

Key words: Brachiaria Brizantha, fertiliser alternative, solid waste.