Does mixed cropping with cover crops improve soil biodiversity?

Published on
April 8, 2015

NWO has recently approved a research request submitted by Ellis Hoffland, Gerlinde De Deyn, Wopke van der Werf en Lammert Bastiaans (Wageningen University) to investigate whether mixed cropping with cover crops is a good idea in Europe. This is a project costing in total nearly € 900,000 so its approval is quite a success story for the Centre for Soil Ecology (ESG + PSG + NIOO).

We know from recent research on natural grasslands and mixed cropping that increased biodiversity leads to increased production and to more organic material entering the soil. This is how organic matter accumulates in soils. This soil organic matter enhances yields and stimulates countless essential functions in the ecosystem, such as carbon fixation, temporary nitrogen fixation (followed later on by mineralisation), water retention and reduced leaching of nutrients into both ground and surface water.

“In this project we’re going to investigate whether this positive effect of biodiversity on organic matter in agriculture is achievable by deploying diversification plus crop mixing,” says Ellis Hoffland. “At present, mixed cropping in main crops is not thought to be practical, so we’re focusing on cover crops, including green manure, trap crops and intercrops. These are cultivated outside the growing season and eventually enter the soil as dead material. We would like to understand which characteristics of plants and their remains are essential for biodiversity. We’re going to investigate which combinations of cover crops improve biomass production and result in more organic carbon, nitrogen and phosphate entering the soil.”

In addition, the project involves investigating crop combinations that result in plant waste with a particular property: it influences soil microbial life in such a way that nutrient leaching and greenhouse gas emission are reduced and disease resistance improved. Resisting disease-causing nematodes is a particularly important function of cover crops; it is not possible to compromise on this function. Ellis Hoffland: “In this way, our project can lead to more green and to greater crop diversification, as well as increased yields in main crops, with less deployment of minerals and pesticides.”