Morphological and productivity responses of Buffel grass (Cenchrus ciliaris) and Guinea grass (Panicum maximum) ecotypes to simulated grazing in a semi-arid environment

Background

Livestock production is an economically significant activity in grassland-based production systems with herbivory, a critical process in modifying plant structure and regulating biomass dynamics in these areas.

Methods

A grazing simulation experiment was undertaken in a semi-arid environment in Kenya to determine the effects of clipping frequency and intensity on the morphology and productivity of Cenchrus ciliaris and Panicum maximum grass ecotypes. The ecotypes were clipped at different frequencies (every 2, 4, and 12 weeks) and different intensities (5, 10, and 15 cm clipping heights). The morphological responses of the grass ecotypes and biomass yields were determined.

Results

The grass ecotypes showed significantly (p < 0.05) varied responses to cutting frequency and intensity. Morphological parameters, tillering, and biomass production were all affected by clipping frequency and intensity. The highest dry matter (DM) yields were recorded under low frequency (LF) clipping, followed by moderate frequency (MF) clipping and high frequency (HF) clipping. LF clipping in C. ciliaris ecotype Kilifi was 20% and 31% more compared to MF and HF clipping. No significant difference in yields was found by cutting the C. ciliaris ecotype Magadi at 4- and 12-week intervals, even though clipping at 2-week intervals cumulatively yielded less biomass. There was a biomass yield reduction in P. maximum ecotype Taveta of 23% and 25% for MF and HF clipping, respectively, while for ecotype Isinya, the reduction was 13% and 15% for MF and HF, respectively. Clipping intensity had a significant (p < 0.05) effect on cumulative yields in C. ciliaris ecotypes, but not P. maximum. Ecotypic differences were apparent in both C. ciliaris and P. maximum ecotype DM yields.

Conclusions

The results in this study suggest that clipping range grass ecotypes less frequently (4- and 12-week intervals) and at 10 and 15 cm stubble heights results in higher biomass yields. Generally, LF and MF grazing and cutting strategies are advantageous for semi-arid lands. Combinations of frequent and high-intensity utilization grazing strategies should be discouraged as they are likely to lead to reduced biomass yields and negative effects both on grasses and on the environment.