Produção de duas gramíneas tropicais submetidas a diferentes lâminas de água e doses de nitrogênio e potássio no estado do Tocantins

• Autor(a) principal: Oliveira Filho, Jair da Costa
• Data de Publicação: 2007
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/799
• topic: Irrigação; Pastagem; Capim-Tanzânia; Capim-Xarões; Manejo de irrigação; Irrigation; Pasture; Tanzânia-grass; Xaraés-grass; Irrigation manegement; CNPQ::CIENCIAS AGRARIAS::ENGENHARIA AGRICOLA::ENGENHARIA DE AGUA E SOLO

Fertilization and irrigation, combined with other cultivation practices, are important factors that allow tropical forage plants to manifest their productive potential under certain soil and climate conditions. Within this context, this work aimed to evaluate the effects of applying different water depths and and nitrogen and potassium doses on the productive characteristics of two tropical forage grasses (Panicum maximum cv. Tanzânia and Brachiaria brizantha cv. Xaraés), under the edapho-climatic conditions in the southern state of Tocantins. Two separate experiments were conducted, one for each grass, in dystrophic Red-yellow Latosol over one year. A split-split plot was used, with the plots consisting of four fertilizer doses, the split plots, six water depths, and the split-split plots, two climatic periods arranged in a completely randomized design with four repetitions. The doses were combinations of N and K2O in the ratio of 1 N:0.8 K2O (D1 = 100 + 80, D2 = 300 + 240, D3 = 500 + 400 and D4 = 700 + 560 kg ha-1 year-1) divided by 12 manual applications, at the end of each 30- day pasture cycle. The water depths were 0, 18, 45, 77, 100 and 120% of crop evaporation, applied by line- sprinkler irrigation, when the matrix potential reached - 40 kPa. Grass collection was carried out using the simulated pasture technique, collecting the forage that could be consumed. In both experiments, the animals were used only as tools . In the dry (fall/winter) and rainy (spring/summer) climatic periods, the following was evaluated: dry matter production (DMP), crude protein (CP) and neutral detergent fiber (NDF), with the following results being obtained: (a) Tanzânia was more productive than Xaraés, with a maximum DMP of 20.215 kg ha-1 year-1, at 630.2 kg ha-1 year-1 of N:0.8 K2O and water depth of 949 mm year-1 (107% of ETc). Xaraés had a maximum DMP of 19.547 kg ha-1 year-1, with a dose of 700 kg ha-1 year-1 of N:0.8 K2O and water depth of 994 mm year-1 (120% of ETc); (b) under conditions of restricted fertilization and no irrigation, Xaraés was more productive than Tanzânia, yielding 12.964 kg ha-1 year-1 of DM; (c) N:0.8K2O doses combined with water depths was effective in ending with forage production seasonality, with dry period production accounting to 47% and 43% of the annual total for Xaraés and Tanzânia, respectively; (d) CP content increased linearly with the N:0.8 K2O doses, except for Tanzânia during the dry period, which responded in a quadratic way; (e) for maximum DMP, the dry period provided the highest CP and the lowest NDF contents; and (f)-Tanzânia outdid Xaraés in DMP and CP and NDF contents.