Towards higher agrobiodiversity – Evaluating the effects of undersowing different flowering species on soybean productivity

Abstract

Context

The loss of insect biodiversity threatens our food security and ecosystem services. This decline is partially linked to intensive agriculture, including monocultures. Alternative cultivation systems with companion plants can create habitats for beneficial insects but may negatively impact crop productivity due to competition.

Objective and methods

To increase agrobiodiversity, we evaluated a cropping system incorporating companion flowering species in soybean cultivation. A total of 16 different flowering species were sown between the soybean rows and evaluated for their impact on the productivity of three soybean genotypes in a two-year trial in southern Germany. The effects of each species on the soybean traits grain yield, protein content, and time to maturity were compared. In addition, their influence on the soil microbiome was assessed to evaluate a further aspect of biodiversity.

Results

In the first year with higher water availability, grain yield was affected negatively by the vigorous species Sinapis arvensis, Sinapis alba and Trifolium resupinatum. In the second year with drought stress, most companion species led to significant yield losses. In addition, maturity was substantially delayed by well growing undersown species. However, protein content, representing grain quality, was not negatively affected in any environment. Furthermore, no significant effect on the soil microbiome could be detected.

Conclusion

In conclusion, a cropping system integrating undersowing of companion species between rows in soybean cultivation is for most species only feasible with sufficient water availability. However, some species, like Linum usitatissimum, seem to be compatible with soybean in such a cropping system even in years with less favourable weather conditions.