Irrigação de plantas forrageiras tropicais e sorgo granífero na região do Arenito Caiuá - Paraná

Abstract

The northeastern region of the state of Paraná, Brazil, is known for its high temperatures, badly distributed rains, and arenite soil characterized by low fertility and erosion. Cattle-raising is the most common source of income on farms in which the deployment of irrigation systems may raise productivity and improve families' income. Current analysis assessed the response potentiality of four tropical forage plants (Moçamba, Pioneiro, Marandu and Tifton 85) and four varieties of grain-bearing sorghum (MR 43, Buster, Catuy and DKB 599) in irrigated and non-irrigated crop systems. Investigation was undertaken on the IAPAR experimental farm in Paranavai PR Brazil, located in the Caiuá sandstone region, altitude 480 meters, with dystrophic red latisol and fractions comprising 89.20% sand, 1% silt and 9.80% clay. The experiment consisted of randomized blocks made up of 2 X 4 factorial design (irrigation and farming). Irrigation management followed water balance in a soil defined by field and permanent wilting point capacity according to characteristic water retention curve. A 0.5 availability factor and water replacement by irrigation was employed so that humidity in field capacity at an effective root depth capacity of 50 cm could be achieved. Experiment in forage plants started on the 16th November 2009 and lasted up to the 28th April 2010, or rather, a 163-day period. Dry mass production per hectare, accumulation rates, dry leaf mass, dry stalk mass, senescent and dead material, and crude protein rates of forage plants were evaluated. Further, sorghum was cultivated for 102 days, from the 10th December 2009 to the 22nd March 2010. Grain production per hectare, one-thousand-seed weight and plant height were evaluated. Irrigation did not cause any increase in forage dry mass, although crude protein in leaves increased. Cultivars Pioneiro, Tifton 85 and Marandu were more productive. In the case of grain-bearing sorghum cultivars, irrigation increased the production of the cultivar Buster, whereas cultivars MR 43 and Buster were more productive than DKB 599 respectively in the irrigation and non-irrigation production system.