Coeficiente de cultura, produção de matéria seca e eficiência do uso da água em capim-tifton 85 no semiárido mineiro

Abstract

The supply of pastures formed with tropical forage grasses has been the main source of food for cattle in the north of Minas Gerais, however the lack of rainfall or poor distribution has been a constant problem for cattle ranchers. In this way, pasture irrigation has aroused great interest on the part of producers, technicians from the scientific community and extension agents.The objective of this work was to determine the culture coefficient, culture evapotranspiration, water use efficiency and dry matter production of tifton-85 grass (Cynodon spp, cv Tifton-85). Four management phases (I, II, III and IV) characterized by cutting ages based on 95% light interception were evaluated, following a completely random-ized design, with five replications, undersemiarid conditions of Minas Gerais State. The grass was managed under cuts in drainage lysimeters, which allowed to determine the water consumption by the plant, obtained by the difference be-tween the volume applied and the drainage, during each cycle. The cuttings were done when the grass reached 25 cm of height leaving a residue of 15 cm. The dry matter production of 10.251, 3.165 and 10.096 kg.ha-1, water consumption of 625, 408 and 1,404 mm, was obtained in summer, autumn and winter/spring, resulting in a water use efficiency of 16,40, 7,76 and 7,19 kg.ha-1.mm-1, respec-tively. The tifton-85 grass growth rate ranged from 0,70 to 1,21 in the summer and fall periods and from 0,62 to 1,40 in winter / spring. There is a seasonality of production of Tifton-85 grass when the minimum temperatures approach 15ºC.