Effects of enclosure management and rangeland sites on chemical composition of herbaceous species in south central Ethiopia

Abstract

This study was conducted in Adami-Tullu Jido-Kombolcha and Arsi Negelle districts, south central Ethiopia. The objectives of the study were to evaluate the interactive effects of grazing management systems and rangeland sites on dry-matter production and chemical composition of herbaceous plants in south central Ethiopia. Data were analyzed using GLM procedure in SPSS 16.0 version, which was used for mean comparisons using post-hoc t-test that can be employed to compare mean differences for enclosure and open-grazed areas. To test the effects of management systems and altitudinal variation on dry-matter production and chemical composition of herbaceous species, mixed model analysis was employed using sample site as a random variable while grazing management systems and altitude were fixed variables. A total of 28 herbaceous species were identified. Of the identified herbaceous species, 20 species were grasses, 2 species were legumes while 6 species were forbs. Among the recorded grass species, some were highly desirable, while others were in the categories of intermediate in terms of desirability and less desirable. We identified the dominant and common grass species that included: Arstida adscensionis, Cenchrus ciliarus, Chloris gayana, Chloris roxburghiana, Bothriochloa insculpta, Eragrostis papposa, Heteropogon contorus, Panicum maximum, Indigofer spinosa, Tephrosia pumila, Sporobolus pyrmidalis, Themeda triandra, B. nigropedata, Ocimum basilicum, Amaranthus dubis, Tribulos terrestris and Achyrantes aspera. The chemical composition of herbaceous plants were analyzed for DM, CP, NDF, ADF, ADL and Ash comparing two grazing management systems and three rangeland sites as patch mosaic units. The results of the present analysis showed that the average CP content in the open-grazed areas was significantly (P<0.05) higher than that of the enclosed areas. The upper and middle rangeland sites displayed significantly (P<0.05) higher CP content for the open-grazed areas than the enclosure management across the study areas. The present findings suggest that the DM, NDF, ADF, ADL and Ash contents of herbaceous species was significantly (P<0.05) lower in the open-grazed areas than in the enclosure management.