Herbage yield and grazing capacity estimation in a tropical coastal savanna rangeland using spatial statistics

Herbage production is known to vary spatially. However, herbage yield (dry matter basis) in the savanna rangelands of Ghana is always generalized leading to inappropriate interventions for herbage improvement. The study sought to employ field survey and geostatistics to determine the spatial variability in herbage yield and grazing capacity in the south-eastern part of the coastal savanna rangelands of Ghana. It was hypothesized that there is spatial heterogeneity in herbage yield and grazing capacity in the coastal savanna rangelands of Ghana. This study employed field survey to estimate point herbage yield and grazing capacity at 109 randomly selected sites. The herbage yield and grazing capacity point estimates were integrated into geostatistics. Estimates of herbage yield and grazing capacity were made for the entire area using ordinary kriging interpolation. The heterogeneity in herbage yield and grazing capacity were evident from the results with herbage yield ranging between 0.58 and 7.21 [tha.sup.-1] and grazing capacity between 0.4 and 4.94 tropical livestock unit (TLU) [ha.sup.-1]. The root mean square errors (RMSE) of prediction were close to the average standard errors (0.98 and 1.06 for herbage yield; 0.79 and 0.71 for grazing capacity) indicating a high precision in prediction. Herbage yield and grazing capacity declined from the western to the eastern parts indicating the need for more functional intervention toward the eastern parts of the study area. Results of the study could be used to facilitate site-specific range management decisions to improve livestock production.