Resumen

MAGALHAES, J.A. et al. Nitrogen use efficiency, yield and composition of andropogon-grass under irrigation and fertilization. Arch. zootec. [online]. 2012, vol.61, n.236, pp.577-588. ISSN 1885-4494.  https://dx.doi.org/10.4321/S0004-05922012000400010.

The effects of different irrigation levels and nitrogen rates on the dry matter (DM) yield, nitrogen use efficiency and bromatological composition of andropogon grass (Andropogon gayanus 'Planaltina') were evaluated. The experiment consisted in a completely randomized block design, with three repetitions, with 2x4 factorial arrangement, being two irrigation levels (50% and 80% of evaporation of the Class A evaporation: ECA) and four N levels (200, 400, 600 and 800 kg/ha/ year) applied as urea, divided in function of the cuts number (16.7, 33.3, 50.0 e 66.7 kg/ha/month). The water supply applied presented similar behaviors in relationship to the total dry matter productivity, leaves and stems. The water supply of 80% ECA provided the smaller leaf/stem ratio. The nitrogen fertilization influenced positively the total dry matter productivity, leaves and stems productivities however, the leaf/stem ratio and nitrogen use efficiency decreased. The crude protein contents of leaves and culms were not affected by water supply, but were increased by N fertilization. The NDF and ADF contents were negatively influenced by the largest water supply. The 50% of ECA irrigation presented the best results, associated to the application of 800 kg of N/ha/year, considering the productivity, bromatological composition and the possibility of economy of water, with consequent reduction in the costs of herbage production.

Palabras clave : ADF; Andropogon gayanus; Class A evaporation; Crude protein; Leaf/stem ratio; NDF.

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