Evaluating controlled release fertiliser for sustainable intensification of agriculture: examples illustrating the value of systems analysis

Increased use of nitrogen fertiliser has been a key feature of intensification of many agricultural systems. While this has improved crop productivity, it has also led to soil acidification, greenhouse gas emissions and contamination of groundwater and surface waters. When the timing and amount of nitrogen supply and demand are not well matched there is a risk of nitrogen losses to the environment. Controlled release fertilisers may provide an opportunity to move towards more environmentally sustainable intensification as these products allow a slow release of nitrogen controlled by the characteristics of their polymer coating (Shaviv, 2001). If synchronized with crop demand this slow release of fertiliser can potentially keep soil nitrogen levels low, improve crop nitrogen-use efficiency and reduce the risk of nitrogen losses.

A number of experimental studies have demonstrated increased nutrient efficiency, reduced nitrate leaching and/or reduced nitrous oxide emissions using controlled release fertilisers (see e.g. studies cited by Chen et al., 2008), but the findings have not been consistent across seasons, soils, cropping systems and management practices (Chen et al., 2008, Venterea et al., 2012). Simulation analyses using an agricultural systems model provide an opportunity to capture the interactions of these factors, which will define where and when controlled release fertilisers may have the biggest impact. The simulations also allow comparisons to be made with alternative management options over a range of climatic conditions.

Here we present the results of simulations that explored the use of controlled release nitrogen fertiliser either as pre-experimentation analyses to inform trials by farmers or as post-experimentation analyses of management alternatives.