What determines a productive winter bean-wheat genotype combination for intercropping in central Germany?

Little is known about optimising the productivity of intercropping through exploiting differences between genotypes. Our study evaluates the performance of three winter wheat cultivars and eight winter faba bean genotypes (experimental inbred lines) sown as replacement row intercrops with sole cropping comparisons. Detailed agronomic, physiological and soil-based measurements were taken over three consecutive autumn-sown seasons at two sites (a marginal versus a fertile soil) in central Germany. This study aimed to contribute to our understanding of key traits required to achieve highly complementary and well-performing intercrops. Faba bean plus wheat intercrops yielded higher than sole crop equivalents at both sites, but more so at the marginal site (34 % > 12 %). High intercrop yields were associated with high wheat component yields. Such stands included faba bean genotypes that exhibited low leaf area index (LAI) values and low plant height. Tall and large faba beans i.e. with high vegetative biomass led to excessive lodging, both as a sole crop and when intercropped. To some extent, this concealed effects of faba bean genotype trait variation that would have otherwise been visible had lodging not occurred. The expression of these traits was heavily influenced by variation in environmental conditions. At the less fertile site, even tall intercropped faba beans showed relatively lower vegetative biomass, which promoted intercropped wheat and led to superior overyielding values and relative yield total. While site-specific differences are key, German winter faba beans need further genetic improvement to refrain from superfluous biomass growth when water resources are plentiful.

Automated summary

This study evaluated the performance of three winter wheat cultivars and eight winter faba bean genotypes as intercrops, finding that intercropping yielded higher than sole crop, especially at the marginal site. High intercrop yields were associated with high wheat component yields. The expression of faba bean genotype traits was heavily influenced by environmental conditions, and further genetic improvement is needed to prevent excessive growth.