Fertilizer release dynamics in relation to biological control: a nitrogen mass balance approach

Fertilizer release dynamics in relation to biological control: a nitrogen mass balance approach
Sean Thackeray, Jackie M. Hill, Grant Martin
Department of Zoology and Entomology, Rhodes University

Increased nutrient loading is regarded as one of the primary mechanisms in driving invasions of freshwater weeds. Highly eutrophic ecosystems are not only susceptible to invaders, but in the case of established water weeds, high plant fitness associated with high nutrient availability often renders the biological control of these weeds ineffective. To understand the interactions of control agents and their associated target plants at different nutrient levels, researchers often need to perform laboratory experiments and it is common practice to obtain different nutrient concentrations with the use of controlled  slow  release  fertilizers.  Very  little  is  known  about  the  nutrient  release  dynamics  of controlled  slow  release  fertilizers  within  aquatic  environments  however,  which  may  change significantly over time thus altering nutrient availability and confounding results. This project aims to quantify the release dynamics of slow release fertilizers in aquatic environments under a range of temperatures, nutrient levels and uptake conditions using a nitrogen mass balance approach. This baseline study will be essential for improving current laboratory strategies for the prediction of a biological control agent’s success at various levels of nutrient loading.