It has been shown that associating trees and crops is more productive than crop rotations separating crops on one side and trees on the other. The biomass production differential is 10-60%. A traditional agroforestry trial conducted by INRA, associating poplars with cereals, showed that a 100ha agroforestry farm produces as much biomass as a 140ha farm separating its crops*. Consequently, agroforestry contributes efficiently to carbon sequestration, through long-term plant biomass and soil, and through the incorporation of organic matter via litter or fine root renewal. Storage values recorded 0.3t of CO2eq/ha/year in intra-parcel agroforestry, and more than 1t of CO2eq/ha/year for certain groves**.
The viability of agroforestry cultivation systems depends on the biological efficiency of the association. Lower intercrop yield is compensated by the product produced long-term through tree sales, provided the unit value of wood is high. If alleys are twice as large than the height of adult trees, it is possible to farm until the trees are cut down, with tree-related income representing 30-50% of total net income.
Agroforestry promotes deeper rooting of trees than in forests. This enables trees to reach a better water supply and avoid water stress, and to recover subsoil nutrients from deep bedrock or leaching. The absence of competition between trees also improves tree diameter growth and therefore reduces the harvest age of trees. Moreover, trees can alter and diversify the microclimate around them (temperature, wind, humidity). This promotes pollinator habitats, and increases pollinator efficiency in case of pest or disease outbreaks.
*Dupraz C., Liagre F., 2008, Agroforesterie – Des arbres et des cultures. Éditions France Agricole, 410 p.
**Pellerin, S. et al. 2013. Quelle contribution de l’agriculture française à la réduction des émissions de gaz à effet de serre ? Potentiel d'atténuation et coût de dix actions techniques. Synthèse du rapport d'étude. 92 p. INRA.