Effect of nutrient availability on competition among pasture species

The effect of N, P and K availability on the growth and competition among pasture plant species was examined in two experiments. In the first experiment, plant communities consisted of six pasture species were developed in wooden boxes for three years using three nutrient treatments, i.e. addition of K and P (treatment –N), N and K (-P) and N and P (-K). Eighteen replicates were used. In the second experiment, five pasture species, in monocultures and mixtures, were grown in pots with sand using a complete randomized design with four replicates. Plants treated with nutrient solution consisted of the combination of two P levels (1 and 20 ppm) and three K levels (4, 16 and 64 ppm). In the first experiment, the changes of species Biomass Duration were negatively correlated with species’ P tissue concentration when P was limited. In the second experiment, dicot species had higher P concentrations in their shoots than the grasses when P was limited. The reverse was found for the grasses. The increase of K availability tended to favour the grasses in the mixtures, while the increase in P availability tended to favour the dicot species. The results indicated that species with minimal tissue concentrations for a nutrient were the most competitive when this nutrient was limited.