Farmer-participatory design and assessment of warm-season legume cereal binary associations for southern Europe

Summary in the original language of the document

Cereal-legume intercropping increases biodiversity at field level, but to ensure satisfactory yield, mixtures must be optimized in terms of crop-type, species proportions and cultivation technique. Adopting a farmer-participatory approach, this research work assessed a set of promising warm-season legume-cereal mixtures for two years under organic farming in Northern Italy (cowpea and soybean-based mixtures) and in Slovenia (common bean-based mixtures) for yield ability and acceptability by farmers. In addition, promising cowpea material evaluated in Italy was tested in Slovenia for one year.
In Northern Italy, six treatments of intercropping (three legume-sorghum mixtures × two spatial arrangements) and four treatments of sole cropping were studied. The three legumes were a determinate-erect cowpea, an indeterminate-climbing cowpea, and soybean. In intercropping, sorghum and one of the legumes were sown either mixed within each row or in alternate rows. In Slovenia, binary associations of common bean with durum wheat, winter wheat and maize were studied. A first experiment addressed the effect of the interaction between two common bean varieties of indeterminate growth type and maize on grain yield, while a second experiment investigated the binary associations of two dwarf growth types of common bean varieties with winter wheat.
Intercropping cowpea and soybean with sorghum under organic farming in Northern Italy was a successful technique to sustain crop yield and at the same time increase biodiversity at the field level. Increasing sorghum sowing rate and identifying genotypes of both legumes and sorghum with a better synchrony in their phenological stages (harvest for silage and for grain) is needed to optimize the studied mixtures. Cowpea breeding for high biomass yield, less sensitivity to photoperiod and shorter reproductive period could contribute to intercropping improvement.
Associating cereals with common bean in Slovenia provided satisfactory yield for bread and winter wheat, whereas for maize the competition between the two species caused a yield reduction of maize in intercropping. Lower yield in intercropping was also measured in common bean. Further studies should address optimal variety choice and crop spatial arrangement to improve intercropping performance.
In both target regions the necessity clearly emerged of adopting techniques to reduce weed growth in the early stages of crop development to ensure the productivity of intercropping.
The evaluated cowpea germplasm in Slovenia showed high potential for organic grain production and breeding.