Effects of fertilizer and grazing sheep on pasture heterogeneity in a small-scale grazing experiment

The presence of plant species and the amount of sheep faeces were recorded systematically across the plots of a fertilizer x grazing randomized block experiment. Sampling sites were classified according to species presence, and the number of classificatory groups was taken as a measure of paddock heterogeneity. Unfertilized plots were more heterogeneous than fertilized plots. Irrespective of fertility level, pastures were generally more heterogeneous at the higher stocking rates. However, the floristic heterogeneity of a plot partly reflected the fertility and stocking level of the neighbouring plots. This suggests that the arrangement of plots within small-scale grazing experiments can influence the results by modifying the botanical consequences of the imposed treatments. The camping and grazing behaviour of sheep also influenced the homogeneity and composition of the pasture of the plots. On the unfertilized plots, these animal-induced differences were as large as those induced by the fertilizer treatments.