Absorção e níveis críticos de fósforo na parte aérea para manutenção da produtividade do Capim-Elefante (Pennisetum purpureum cv. Napier)

Abstract

The experiment was carried out in the field, during two years, to evaluate the phosphate fertilizing residual effect implantation over the phosphate absorption and critical levels in the plant for the elephant grass (Pennisetum purpureum Schum. cv. Napier) maintenance. The treatments were arranged according to the factorial 2 X 2 X 5, in blocks randomly lined with three repetitions, and consisted of two phosphate application ways (located in the bottom of the hole and distributed in the hole with incorporation), two spacing between the plantation lines (0,5 and 1,0 m) and five levels of phosphate correspond to the 0, 30, 60,100 and 150 kg/ha P doses and to 0, 60, 120, 200 and 300 kg/ha of the P2O5 to the applications localized and distributed, respectively. Seven plant harvesting were done from the plants in the parcel central hole (lines), corresponding to 2 m2. After weighing the harvested forage, samples were taken to determinate the dry matter content (DM) and the phosphate in the DM. After each cut, a dressing fertilization with potassium and nitrogen covering (67 kg/ha of N and K2O, using ammonium sulfate and potassium cloret). The highest phosphate content in the plant DM was observed when the fertilizer was distributed and incorporated to the plantation hole. The phosphate critical level in the plants DM presented an average level of 0.13 dag/kg, without great variations due to the application way and, or, to the spacing between the plantation lines.