Faba bean in cropping systems

Summary

The grain legume/pulse faba bean (Vicia faba L.) is grown world-wide as protein source for food and feed and simultaneously faba bean offers ecosystem services such as N2 fixation and diversification of cropping systems. Even though the global average grain yield has almost doubled during the recent 50 years the area of faba beans has declined with 56% in the same period. This is especially the case for some of the former big producer countries such as China and Egypt. The yield season-to-season of faba bean and development of an industrialized agriculture based on fossil fuels (= N fertilizers, heavy mechanization) are some of the explanations for this development. Studies of faba bean in cropping systems have focussed on the effect of faba bean as a pre-crop in mainly cereal rich rotations, whereas the effect of pre-crops for faba bean is lacking. This is contributing to yield variability. It would be of interest to elucidate the main biotic and abiotic stresses causing the yield variability by growing faba bean in more optimal conditions in term of fertile soils, sufficient water supply and optimal place in the rotation. Analysis of nutrient accumulation in faba bean at maturity showed that faba bean has a higher requirement for nutrients (except Ca) than pea types. A major aprt of the faba bean potassium is recycled to the soil via the residues. Faba bean is one of the crops, which has the highest N2 fixation among cool season grain legumes (c. 70-95% N derived from fixation) and consequently the N benefit for subsequent crops is often high. Several studies have shown that N-fertilization to the subsequent crop can be significantly reduced (30-100 kg N ha-1). There is, however, a requirement for more and improved assessments of the environmental effects of faba bean on nitrate leaching and emissions of N2O to the atmosphere as a consequence of N2 fixation and nitrogen rich plant residues. It is equally important to develop improved preventive measures, such as catch crops, intercropping, no-till, in order to minimize unwanted effect on the aquatic environment and climate. Combined with research that can lead to reduced of yield variability, the faba bean crop may prove to be a key component of arable cropping systems in a future with declining availability of fossil energy for fertilizer synthesis and the requirement for an agriculture with less impact on the environment and the climate