The machine that calls rain: the secrets of agroforestry

We know it since at least Christopher Columbus: forests, sources of life and oxygen, also call the rain. Cutting them, pushes to desertification of species and soil.

As a regenerative solution, agroforestry refers to new or historical practices involving trees, crops and / or animals on the same agricultural parcel, on the edge or in the open field.

These practices include agro-sylvicultural systems but also sylvo-pastoral, pre-orchards (animals grazing under fruit orchards) …

The contributions of the tree in an agricultural environment are numerous:

Improve plot production by optimizing the resources of the environment

The French INRA experiment on a wheat-walnut system at Restinclières (Hérault) showed that a 100-ha agroforestry plot could produce as much biomass (wood and agricultural products) as a plot of 136 ha where trees and crops would have been separated. , a gain of 36%. This intensification of production results from a better use of the natural resources of the environment: light, water and fertilizers are harvested more efficiently thanks to the staging of crops, root systems of various depths, permanent land use …

Complementarity search: for example, the tree goes back up water and minerals from the deep soil layers to make them available to surface crops. The creation of a micro-climate on the plot also protects crops and animals from thermal and water stress. The tree could notably help to mitigate climatic accidents, partly responsible for the stagnation of grain yields in Europe

Diversify plot production

Trees make it possible to diversify services and sources of income on the farm: agricultural production, timber, energy wood, fruit, fodder, litter, mulching …
Restore soil fertility

The trees release organic matter through the leaves that fall to the ground and the decomposition of the roots: 40% of the biomass of a tree returns to the ground each year. The roots also structure the soil, facilitating its biological activity. These contributions therefore improve the fertility of the system.

Guarantee the quality and quantity of water

A study (Agroof, INRA, Rhône Méditerranée Corse Water Agency contract) has highlighted the capacity of depollution of trees. True filters, they limit some of the leaching of nitrates, thus reducing the pollution of groundwater. This function is particularly interesting for the management of drinking water catchment areas. In addition, the root systems of trees increase the useful water reserve (exploitable by the plant) of the soil, improve the infiltration of runoff, limit the evaporation of soil …

Improve biodiversity levels and rebuild an ecological fabric

The diversity of woody and herbaceous species improves soil life where fungi (mycorrhizae) play a major role. Wooded infrastructures provide habitats and food for an important flora and fauna procession (auxiliary crops – bees and other pollinators -, game, predators of pests …) They contribute to the restoration of ecological continuities at the scale of territories.

Storing carbon to fight climate change

99% of the solid matter of the tree comes from atmospheric CO2: trees are therefore excellent carbon sinks. A mature ash tree, for example, almost 3kg of CO2 per year. Trees not only help mitigate the effects of climate change but also adapt, as they recapitalize soils into carbon, a source of fertility.

Challenges

Beyond driving an agricultural parcel, agroforestry is part of territorial projects (energy, food …):

• Water management at catchment scale
• Increased Wood Requirements / Land Competition
• Sustainability of beekeeping (quality and diversity of resources)
• Continuity and ecological corridors
• Leisure and outdoor activities (hunting, fishing, hiking, agri-tourism …)

The development of techniques

If the first research projects in France consisted mainly of aligning monospecific trees in the middle of crops, agroforestry as it is recognized and developed today fully integrates hedgerows and updates farmers’ know-how. Its effectiveness is based on a wide variety of species, techniques, types of development or tree sizes to reconcile biomass production and environmental protection.

Multi-species plantations / enhancement of the existing borders and full field / natural regeneration / restoration of tadpole trees, introduction of linear coppices

Complementary to the management of the tree, soil conservation techniques (simplified cultivation techniques, plant cover, direct sowing, etc.) mimic the functioning of natural ecosystems (meadow, forest) and recreate soil humus. Farmer’s objectives: reduction of inputs, limitation of erosion, diversity of outlets.

There are now agroforestry projects that combine fruit production with medicinal plants, vegetables or cereals.

To know more

This article is largely inspired by the French Association of agroforestry which provides training in France.

Find Martin Crawford’s book on forest gardens: Creating a Forest Garden Working with Nature to Grow Edible Crops

The syntropic farming of Ernst Gotsch