Effect of Nitrogen Sources and Harvesting on Four (4) Grass Species in Southern Guinea Savanna of Nigeria

The study on the influence of nitrogen sources and cutting intervals on the digestibility of four (4) grass species was carried out during the 2006/2007 cropping season at the Teaching and Research Farms of the University of Agriculture, Makurdi. The objectives of the study were focused on feed supply as major constraints to ruminant livestock production by evaluating Andropogon gayanus, and three (3) other grass species to identify promising genotypes suitable for exploitation and acceptability to livestock. There were twenty four (24) treatment combinations replicated three times, in a split-split design. The grass genotypes (Andropogon gayanus, Panicum maximum, Cynodon nlemfuensis and Pennisetum purpureum); Nitrogen sources (Mineral fertilizer, legume and zero-nitrogen) and cutting intervals (6 and 9 weeks) constituted the main plot, sub-plot and sub-sub plots, respectively. Among the grass genotypes tested, the highest mean crude protein (CP) was produced by Pennisetum purpureum (117g/kg), which was significantly higher than those produced by Andropogon gayanus (107g/kg) and Panicum maximum (101g/kg).However, P. purpureum recorded the least ADF (281g/kg) and NDF (511g/kg) values respectively, which were significantly lower than those produced by the rest of the grass species. The effect of nitrogen sources revealed that the legume inter-crop sources produced the highest and significant values of CP and EE (119g/kg and 29g/kg respectively), but the zero-N source produced the highest and significantly amount of ADF (299g/kg) and NDF (625g/kg). The effect of cutting interval showed that only CP value was significantly increased at 6 weeks cutting than at 9 weeks, but the EE, ADF and NDF values recorded their highest values at 9 weeks cutting than at 6 weeks cutting. The interaction effects result revealed that irrespective of the N-sources (Mineral-N, Zero-N and Legume-N); P.purpureum yielded the highest CP values.