Yield Variability Affects Grower Interest
PARIS - Nov 4/15 - SNS -- Greater yield variability than in North and South America probably explains one reason European farmers grow less legumes, believe INRA scientists in Versailles-Grignon.
The researchers note that pulses and other legumes offer 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.
Researchers looked at yield data between 1961 and 2013, and in each of the four regions of Europe (Western, Eastern, Northern and Southern Europe) and two regions of America (North and South).
They compared the five grain legumes cultivated most widely in terms of land area with the five main non-legume crops grown in each area. Yield variability from one year to another and the risk of a yield being lower than a loss threshold was examined for each crop choice.
Legume Yields More Variable in Europe
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.
It turns out that yield variability for lupin is 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 fababean was the most stable species in Southern and Western Europe, soybean in Eastern Europe and pea in Northern Europe.
Americas Yield Variability Similar
In America, the comparison between legume and non-legume crops was more in favor 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 characterized 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.
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