Irrigation and nitrogen fertilization of three forage grasses in Midle-North of Brazil

Abstract

The objective of this study was to evaluate the effect of different irrigation depths and nitrogen fertilization rates on the average dry matter productivity (DM) and crude protein content (%CP) of three forage grasses. The work was carried out at Embrapa Meio-Norte experimental area, located in Parnaíba, Piauí State, Brazil. The studied grasses were Pennisetum purpureum, cv. Pioneiro; Panicum maximum, cv. Tanzânia, and Cynodon spp., cv. Tifton-85. The irrigation depths were applied according to a class “A” evaporation pan (0.2; 0.6 and 1.0). The fertilization rates used were 100; 200 and 300 kg/ha of N (urea), broadcast applied, fractioned according to the number of cuttings. Five cuts of the grasses were processed in the evaluation period. The DM yield of the cv. Tanzânia (24.984 kg/ha) was superior to the DM yields of the cv. Tifton-85 (18.231 kg/ha) and cv. Pioneiro (16.239 kg/ha). The combination of the irrigation depths corresponding to 0.2 ECA with the fertilization level of 200 kg/ha of N, yield the best results. The effect of N rates on the CP content was linear and significant (P <0.05) and the average CP content of Pioneiro (15.58%) superior to those of the Tanzânia (12.82%) and Tifton-85 (12.85