Research NoteDifferent responses of Eragrostis curvula and Themeda triandra to rapid- and slow-release fertilisers: insights into their ecology and implications for fertiliser selection in pot experiments

Abstract

In a pot experiment, we examined the response of Eragrostis curvula and Themeda triandra to 0, 15, 30 and 60 g m^–2 of nitrogen (N) supplied either as a rapid-release fertiliser (Sasol Nitro NPK) or a slow-release fertiliser (Plantacote Plus). Both E. curvula and T. triandra increased linearly in biomass with increasing levels of the slow-release fertiliser, achieving similar maximum biomass (75 g vs 71 g, respectively) at the highest level of the slow-release fertiliser. However, only E. curvula peaked at the highest level of the rapid-release fertiliser, whereas T. triandra did not show any increase in biomass beyond 15 g m^–2 of N supplied by the rapid-release fertiliser. This resulted in considerably less biomass achieved by T. triandra under the rapid- than slow-release fertilizer (29 g vs 71 g, respectively) and in comparison to the maximum biomass of E. curvula under the rapid-release fertiliser (29 g vs 87 g, respectively). Thus, T. triandra was intolerant of high concentrations of N. This has implications for choosing the correct type of fertiliser according to the objectives of an experiment and for understanding the response of these grasses to fire, mowing, grazing and fertilisation.

Keywords: fertilisation; nitrogen; plant strategy; tolerance

African Journal of Range & Forage Science 2009, 26(1): 43–46