Potential of Greenhouse Gas Production by Guinea Grass Subjected to Weed Competition

The world population growth and the increasing purchasing power have raised the demand for animal proteins, especially meat and milk. This has made it essential to intensify livestock production by making it productive, efficient and at the same time sustainable, which today is a great challenge for cattle ranchers. The objective of this study is to evaluate the effects of coexistence with weeds on productivity, nutritional quality and potential of greenhouse gas (GHG) emission by Guinea grass (Panicum maximum cv. Mombasa) in pasture renewal conditions. The experiment was set up in randomized blocks, four replications, with treatments consisting of eight periods of coexistence: 0, 15, 30, 45, 60, 75, 90 and 120 days after seedlings emergence. Phyto-sociological evaluations were performed in the weed community at the end of each coexistence period. The Guinea grass was evaluated as for morphological, chemical and bromatological parameters and as for the potential of total gas, methane and carbon dioxide emission. The results show that productivity, nutritional quality and energy value of Guinea grass decreases proportionally to the increase in the period of coexistence with weeds. The non-coexistence with weeds provides a better in vitro digestibility of organic matter and, consequently, decreases the GHG emission potential by the dry matter of Guinea grass.