Avaliação do potencial do girassol (Helianthus annuus L.) como planta forrageira para silagem e para associar-se ao capim-elefante (Pennisetum purpureum Schum) na ensilagem

Abstract

The agronomic and chemical characteristics of sunflower cultivars (Helianthus annuus L.) in the silage production, harvested at 95, 110, and 125 days after sowing were analysed. The sowings were done in November 04th 1998 and March 03rd 2000 for the normal and fali crops, respectively at two sowing densities (40,000 and 60,000 plants/ha). In the, normal crop, the hybrids Cargill C-ll, Brascallb DK-180, DK40-40, Morgon M-92007, M-742 and the variety V-2000 of EMBRAPA were used. In the fali crop, the hybrids M-742, M 92007 and the variety Catissol 01 were utilized. The mineral fertilization was performed by applying in the ridge , at sowing , 300 kg/ha of the formula 08-28- 16 + zinc at40 days after sowing, topdressing , 30 kg of N via soil and 1kgof Borum and 1 kg of zinc per hectare via leaf were done . The design was that of randomized blocks with 4 replicates in factorial (2x6x2 and 2x3x3) scheme , the factors being sowing density, cultivars and cutting season in the same order for 1998 crop and 2000 fali crop , respectively. At the moment of harvest ,determinations of the total number of plants, number of lodged plants and height of plants, in the two central rows of the plots were accomplished . The plants were chopped mechanically in particles 2-3 cm in size, ensiled for 30 days in PVC silos 10 cm in diameters , 40 cm in length . In addition , the percentage and yield of dry mater, crude protein (CP) , ether extract (EE) , neutral detergent fiber (NDF), in vitro digestibility of dry matter ( IVDDM) and pH of the silages were evaluated. The average dry matter yields were of 8.51 and 7.03 ton. /ha for the period of the crop and fali crop, respectively. In the silagens, the average values in percentage were 5.14 and 5.16 for IDDM , 14.42 and 11.99 for EE .11.81 and 10.09 for CP , 54.84 and 39.98 for NDF and 4.78 and 4.78 of pH in the crop and fali crop , respectively. The results, in general, allow to conclude that there are chemical differences in sunflower silages with regard the cultivar ,ensilage season and sowing density. In a second experiment, sunflower was used to associate with elephant grass in the silage (Pennisetum purpureum Schum ). The harvest of elephant grass was accomplished manually after 70 days of the equalization cutting at a height of 10 cm from he soil surface . Were made from silages, the sunflower hybrids M- 92007 and M-742. The mixes of sunflower + elephant grass were done at the following proportions of green matter: 100% grass, 75 and 25%; 50 and 50%; 25 and 75% of grass and sunflower respectively and 100% of sunflower. The experimental design used was the completely randomized with 4 replicates . The procedures utilized in the evaluation of the nutritious value of the silages were the same utilized in the previous experiment. The results allow to conclude that elephant grass silages with associatíon of whole sunflower plant presented larger percentages of DM, CP, EE and pH values , increases in IVDDM, and also a smaller percentage of NDF in the dry matter with increasing leveis of associatíon.