The objective ofthis study was to estimate the effect of three sowing dates: October (early),November (normal) and December (late), on the phenological, yield and qualitativetraits of four sunflower hybrids: Rumbosol-91 (forage), M-734 (double purpose),C-11 (double purpose) and BRS-191 (grain) grown for silage making. A 4 x 3 factorialtreatment combination (four hybrids x three sowing dates) was allocated in arandomized block design with four replications. The October sowing brought aboutlonger cycle, higher plant height, and smaller seed head diameter and contributiondue to the prevailing climatic conditions of lower temperature, insolation andphotoperiod during the crop growth period. The Rumbosol-91 and BRS-191 hybridssowed in November showed higher lodging plus stalk breaking proportion of about49.6 and 65.7%, respectively. The BRS-191 and M-734 hybrids sowed in Decembershowed higher biomass yields of 39.71 and 43.76 t ha-1 fresh matterand 11.31 and 11.41 t ha-1 drymatter, respectively. While the CPcontent increased, the NDF, ADF and ADL contents decreased from the stem, tothe leaf and to the head plant fractions. The whole plant DM values ranged from23.2% in the Rumbosol-91 hybrid sowed in November to 47.9% in the C-11 hybridsowed in December, indicating that the hybrids have differentiated moistureretention capacity at similar physiologic maturity of the culture (R-9 phase).The CP values ranged from 7.0 to 15.7%, an evidence of the high protein contentof the culture. The ADL values of the whole plant ranged among 6.5 to 12.4%,with lowest values for the M-734 hybrid sowed in December and C-11 hybrid sowedin October. The M-734 hybrid sowed in December has better relationship amongphenology, yield and bromatological composition, traits required for the makingof high quality silage.
