Animal, Wildlife and Grassland Sciences
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Browsing Animal, Wildlife and Grassland Sciences by Author "Botha, P. R."
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Item Open Access Evaluation of techniques to determine the production potential of cultivated pastures(University of the Free State, 2009-12) Vermeulen, Sunet; Snyman, H. A.; Botha, P. R.English: For farm managers to utilize their pastures more efficiently, it is essential to estimate both herbage biomass and botanical composition. Therefore, there is a need to estimate herbage biomass and botanical composition of cultivated pastures with simple, accurate and cost-effective methods instead of the more accurate, but time-consuming destructive methods. The objective of this study was to evaluate non-destructive methods for estimating herbage biomass and/or botanical composition on different mixed-species pastoral systems for beef and/or dairy cattle and to identify the method, if any, that would be most accurate in each particular pastoral system. A comparison of the rising plate meter, the comparative yield method and the meter stick was conducted to determine the predictability of these non-destructive methods for estimating herbage biomass. Furthermore, the dry-weight-rank method for determining species composition was compared to hand clippings. The accuracy of the different non-destructive methods for estimating herbage biomass was compared using the coefficient of determination (r2) values between cut material and herbage biomass estimates. The study indicated that the meter stick (r2 = 0.79 – 0.85) provided the most accurate values for the dairy pastoral systems. In the beef pastoral systems the rising plate meter (r2 = 0.76 – 0.83) resulted in the most accurate method, for three out of four of pastoral systems. It was clear that species composition of the stand was an important factor affecting the accuracy of herbage biomass estimates. Based on the results of this study, all of the non-destructive herbage biomass estimation methods tested are suitable for use on both farm-level and pasture studies on larger areas. However, in grazing studies that are conducted on relatively small areas and with a relatively small number of animals, these methods may be less accurate and where accurate herbage biomass is desired, cutting is still recommended. Furthermore, the results indicate that the dry-weight-rank method of analysis is an accurate means of determining the botanical composition of both cultivated dairy and beef pastoral systems. The contribution of 92% and 96% of all species within the dairy and beef pastoral systems, respectively, was estimated within 5% accuracy of the “true/actual” value of species determined by hand clipping. These methods for determining herbage biomass and botanical composition can serve as a useful tool to set stocking rates at levels necessary to balance forage supply and demand in pastures that may have uneven species composition. These measurements are essential to make sure that animals are adequately fed and swards not under- or overgrazed and therefore ensure sustainable animal production.