Despite their agronomic value, legumes are cultivated much less in Europe than in America. INRA scientists in Versailles-Grignon have demonstrated that crop yields vary more in Europe than in America, and have thus contributed to identifying the legume species and regions most favourable to their development in our part of the world.
Pea, field bean, lupin, etc. are legumes that have numerous agronomic advantages. But paradoxically, they are planted on less than 2% of arable land in Europe, versus more than 15% in North America and 26% in South America. European farmers often consider these crops to be too risky, apparently because their yields vary more from one year to another than those of non-legume crops such as cereals. It is this hypothesis that INRA scientists in Versailles-Grignon decided to explore by analysing the inter-year variability of grain legume and non-legume crop yields in Europe and America over a 53-year period.
Methodology
The INRA scientists from Versailles-Grignon used data from the United Nations Food and Agriculture Organization (FAO) on yields and crop areas for their study. Over the period from 1961 to 2013, and in each of the four regions of Europe (Western, Eastern, Northern and Southern Europe) and two regions of America (North and South), the five grain legumes cultivated most widely in terms of land area (which include peanut, faba bean, field bean, lentil, lupin, pea, chickpea, soybean and vetch) were compared with the the five main non-legume crops (which include oats, wheat, rapeseed, barley, potato, rice, rye, sorghum and sunflower). For each crop, they evaluated yield variability from one year to another and the risk of a yield being lower than a loss threshold.
In Europe, legume yields are more variable than those of non-legume crops
Whatever the indicators for variability and risk, the scientists demonstrated that in Europe, the yields of grain legumes varied more than those of non-legume crops.
Whilst the yield of wheat - the cereal most widely cultivated in terms of surface area in Europe - displayed the smallest inter-year variability, that of legumes always varied more (except for faba bean in Southern Europe). Thus lupin displayed variability that was five to 45 times greater than that of wheat in three out of the four European regions (Northern, Eastern and Western). In Southern Europe, the field bean was the most variable legume crop, followed by soybean. Inversely, the faba bean was the most stable species in Southern and Western Europe, soybean in Eastern Europe and pea in Northern Europe.
In America, the yield variability of legumes is more similar to that of non-legume crops
In America, the comparison between legume and non-legume crops was more in favour of legume crops than in Europe. In North America, only three species of legume (lentil, pea and peanut) displayed a variability greater than that of wheat, and this concerned only two species in South America (peanut and vetch).
The scientists showed that yield variability and the risk of yield losses of soybean were very similar to those of wheat in both North and South America. Soybean even displayed less variability than maize in North America. The team observed that the species with the highest degrees of variability tended to be cultivated on small areas of land (e.g. all legumes in Europe), while species cultivated on larger areas displayed smaller degrees of variability (e.g. soybean in North and South America). However, species cultivated on smaller areas did not always display higher degrees of variability, which suggests that yield variability is one of several factors to explain the land area cultivated with a particular species at the scale of a major region.
Overall, this study showed that the yields of legume crops were generally more variable than those of non-legume crops in Europe. However, the degrees of variability differed as a function of species and region, which could be explained by different pest pressures (insects and weeds), cultivation systems or pedoclimatic conditions. Historical changes to the Common Agricultural Policy (CAP) or strong competition from American soybean imports affecting legumes grown in France are also elements to be taken into account when trying to explain the degrees of variability observed. This study has nonetheless contributed to identifying the grain legume species and regions that are less at risk, in order to encourage the expansion of these crops in Europe.
Legumes under the microscope
Legumes are characterised by the presence on their roots of nodules which contain bacteria of the Rhizobium genus that are able to fix atmospheric nitrogen and render it assimilable by the plant. Their grains are held inside a pod.
They belong to the Fabaceae family which comprises 18,000 species, or approximately a twelfth of all the flowering plants known. Species that are cultivated include grain legumes such as field bean, pea, lentil, peanut, soybean and lupin, and forage legumes such as alfalfa, clover and sainfoin.
Legumes are an important component in both human foods and animal feeds, thanks to their high contents in protein and essential amino acids. Cultivated alone or in combination, they play a major role in rotations in terms of improving soil structure, supplying nitrogen to associated or succeeding crops, and competing with weeds in the case of some species, particularly forage legumes. Finally, new markets have recently been developing in the fields of bioenergies or biomaterials.
reference
Cernay, C., Ben-Ari, T., Pelzer, E., Meynard, J.-M., Makowski, D. (2015). Estimating variability in grain legume yields across Europe and the Americas. Scientific Reports - 5,11171 DOI: 10.1038/srep11171
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