Effects of fertilisation on soil life and nitrogen cycling: new insights, better decisions

Results and recommendations Above-ground fertilisation: a promising method

A striking result of our research is that above-ground fertilisation offers an interesting course of action with significant benefits for farmers and the environment. Advantages of above-ground fertilisation include:

• It stimulates micro-organisms that can fix nitrogen for free. This provides an opportunity to save on artificial fertilisers. Saving on artificial fertilisers reduces the risk of nitrogen leaching into the environment while reducing costs.
• It fits well with the Climate Adaptive Netherlands action programme because it also stimulates micro-organisms that make the soil more drought-resistant.
• It can potentially reduce emissions of greenhouse gases such as nitrous oxide and methane. Further studies with emission measurements are needed to confirm this.

Digestate from mono-manure fermentation: opportunities and challenges

The use of digestate as a fertiliser is controversial, mainly because of the fear of pathogens and the idea that it is at the expense of soil biodiversity. However, our research shows that using digestate as a fertiliser does not increase the risk of pathogens. In fact, digestate fertilisation has a number of advantages over slurry fertilisation.

Because of these positive effects on soil health and the environment, digestate appears to be a better fertiliser than slurry in certain circumstances.

There are also challenges to using digestate. Digestate is a quick source of nitrogen, which is beneficial for plant growth, but this also stimulates nitrifiers in the soil, increasing the risk of nitrate leaching. More research is needed to determine the optimal use of digestate.