AGROECOLOGY lab

To what extent is current knowledge on monocrops transferable to intercrops? On grassland plant communities to crop mixtures? On mineral fertilizer to organic fertilizer? On yearly studies to long-term practices?

Intercropping is the simultaneous cropping of at least two different crop species. This ancestral practice has been regaining interest in recent years because it fits well the agroecological principles. Yet we observe little enthusiasm for intercropping among (organic) farmers, namely because of its unpredictability and a high risk of crop failure. However, little is known on the microbiome underlying successful intercrops, and the role of long-term farming practices in shaping this microbiome. 

Within the context of organically grown grain legume-cereal intercrops for human consumption, which type of soil microbiome makes or breaks an intercrop? For the legume-cereal intercrop to succeed, many soil organisms need to work in concert. We hypothesize that part of the intercrop unpredictability is due to a local lasting imprint from past farming practices on the soil microbiome. Indeed, their effect on soil fertility is cumulative. Recalcitrant compounds or microorganisms contained in organic fertilizers may not directly benefit the current crop, but rather foster long-term soil fertility, thus benefitting succeeding crops. The same can be said of (legume) (inter)crop residues that are left on the field and have been shown to affect succeeding crops over several growing seasons. Manure is known to have a lasting cumulative effect, as is the withdrawal of manure over a long period. Similarly, tillage intensity,  presence or absence of grass leys in the rotation, use of mineral fertilizers or not, repeated pesticide use all have been shown to impact the soil biome, soil fertility and harvest outcome. Nonetheless, farm and field history are rarely considered in field studies, especially those investigating microbial processes.

Organic farms are not easily studied as they are often highly diversified systems and resort to chemically complex and diverse “organic fertilizers”. We hope to contribute to the disentanglement of the role of farming practices and recent farm and field history on intercrop functioning via legume-cereal-soil microbe interactions.