Recuperação de pasto, associada à produção de silagem de sorgo e madeira, em sistema de integração lavoura-pecuária-floresta

Abstract

Systems Integration crop-livestock-forest (ICLF) come standing out as an alternative to the recovery of degraded pastures in the ecological scope.In the northern region of Minas Gerais the situation of the pastures are not much different from that observed in the country, being commonly found pastures in typical situation of degradation. Given the importance of looking for alternatives for the restoration and renovation of degraded pastures in this region, as well as for the rest of the country, and of the need to know the real potential of the ICLF in renewal of these areas and alternatives to feeding of the cattle in front of the food shortages in the dry season, three experiments were realized. The tests were performed in order to evaluate: 1 - the productivity of forage sorghum, forage grasses perennials and estilo; 2 - the production of clonal eucalyptus trees (Eucalyptus grandis Hill ex Maiden x E. urophylla) and acacia (Acacia mangium Willd.) when grown in ICLF; and 3 - the fermentative characteristics of sorghum silage added of different percentages of forage. The experiments were conducted in an area of ICLF established for 11 months, located at the Institute of Agricultural Sciences of the Federal University of Minas Gerais, in Montes Claros - MG. Were tested three species of forage grasses intercropped with sorghum and eucalyptus or sorghum and eucalyptus + acacia: Brachiaria brizantha (A. Rich ex Hochst.) Stapf., cv. Marandu, Brachiaria decumbens Stapf., cv. Basilisk and Panicum maximum Jacq., cv. Tanzania, cultivated or not, in consortium with estilo (Stylosanthes capitata Vog. + S. macrocephala MB Ferr. Cost Sousa et cv. Campo Grande). The seeding of sorghum and forage were realized in January 2010 in no-tillage system. The spacing of sorghum was 0.5 m between rows and forage sown the haul, respecting the distance of 1.0 m of arboreous plants in intercropped plots and harvested at 98 days after sowing (DAS). The eucalyptus and acacia trees there were 11 months old with average heights of 3.83 m and 2.47 m, respectively, and were cultivated in 10 x 2 m spacing, in consortium portions of ICLF and also established in monoculture in the spacing 3 x 2 m. The characteristics of productivity of sorghum and of the perennial forage were obtained at the time of harvest at 98 DAS, and the growth and productivity of trees were measured at 13, 18 and 25 months after transplanting. The eucalyptus, acacia and species of forage did not influence the productivity of sorghum for silage, but the pasture establishment was compromised because of the decreased of the stand of forage evaluated at 30 and 98 days after sowing. The proximity of the trees and the competition imposed by this component reduced the growth of sorghum plants. Regarding the arboreous components, it was observed that height growth of eucalyptus was influenced by the consortium with acacia in the arrangements studied in the ICLF, but the diameter at breast height was not influenced by the arrangements. The arrangement of species of eucalyptus and acacia in consortium in the same row of planting has volumes per hectare, and mean annual increments at 25 months of age similar to that observed in the arrangement using only eucalyptus in the rows of planting of the ICLF. In the assessment of the bromatological characteristics of sorghum silage with addition of 15 and 25% Marandu grass and Tanzania grass at the percentage of total green matter of sorghum cultivated in the ICLF, harvested at 98 days after sowing, we obtained that the addition of Marandu grass and Tanzania grass decrease the quality of sorghum silage produced, due to the higher proportion of fiber in these grasses; decrease the protein content, mainly due to increased of the protein content associated with the unavailable portion of the nitrogen. The increment of the grasses produced silages with higher pH values, but the contents of ammonia nitrogen and acid detergent insoluble nitrogen obtained are indicative of well-conserved silage. Thus, the ensilage of sorghum with up to 25% of Marandu grass or Tanzania grass, percentages common in areas of integration crop-livestock and crop-livestock-forest, reduces the quality of silage produced, however, does not derail its production and its use in animal feed.