ClimatVeg climate change adaptation project: towards more efficient irrigation

Heatwaves, storms, floods... Climate change is disrupting crops and worrying farmers. How can crops be adapted to our current situation? What crops should be grown, and what working methods to use? The ClimatVeg project was launched in 2021 to answer these questions. Spearheaded by Vegepolys Valley, the competitiveness cluster devoted to plant life, and financed by the Bretagne and Pays de la Loire regions, this large-scale programme brings together several agricultural sectors and more than 20 complementary actions, calling upon a variety of disciplines. All in all, about 80 partners are involved, including chambers of agriculture, research centres and producer groups.

IMT Atlantique is contributing to ClimatVeg via the Energy Systems and Environment department (DSEE), bringing to the project expertise in water treatment and quality. The faculty members are working on a key issue for the agricultural world: irrigation efficiency. "We are looking at how to recover water, store it and ensure that it is available at all times - and particularly in the summer - in sufficient quantity to meet the needs, while preserving its quality," explains Valérie Héquet, a faculty member in the DSEE.

Three types of reservoirs to compare results

To achieve this, the team uses an original experimental site at the Maison des maraîchers, in Pont-Saint-Martin, near Nantes. The site contains greenhouses where run-off waters are collected and stored in three reservoirs, each one with a capacity of around 200 m3, filled with measuring instruments. The first one is left in the open air; the second one is fitted with a coconut fibre mat on which aquatic plants grow, forming a sort of 'floating swamp'; the third one is covered with a synthetic blanket made of plastic pieces, designed to slow down evaporation. The purpose is to compare the measured results of each reservoir, using a series of parameters: quantity of evaporated water, but also oxygen content, presence of ionic species, organic matter, suspended matter, micro-plastics, presence of pesticides, etc.

"We develop evaporation models, based on input/output balances and depending on weather conditions (wind, sunshine, etc.)," explains Valérie Héquet. At the same time, we are monitoring the biological and chemical quality of the water as accurately as possible". Ultimately, the partners in this initiative, coordinated by the Pays de la Loire Chamber of Agriculture, plan to produce a practical guide for professionals, with different sections depending on the type of crops, technology used, biodiversity, etc.

A case study for engineering students

Students are benefiting from the educational advantage of the project, especially the 3rd year Energy-Environment students who work on it half a day per week. They take samples, record data, study evaporation models and measure airborne pesticides and micro-plastics. "It is a very concrete work, which helps them to become aware of the limits of theoretical models," observes the researcher. "It also gives them the opportunity to meet the people involved in the industry and learn about the regulatory aspects."

After two years of experiments and measurements, the first lessons are beginning to emerge. For instance, in the "floating swamp" reservoir, the plants have enough nutrients: "They vegetate during winter, experience a growth peak during spring, then curl up during summer," notes Valérie Héquet. But biodiversity is preserved". To refine its observations, the team needs another 2 or 3 years - in particular to compare the measured results from one year to the next. "Realistically, there will not be only one single solution," says Valérie Héquet, "each one has its own characteristics and advantages in response to the use we want to make of this water resource."

There will also be the question of multiple uses - leisure, fishing, fire-fighting, etc. - particularly in the case of large reservoirs, known as 'bassines'. A sensitive topic, as recent events have shown... To which this work will provide concrete references that can be shared with water stakeholders and other plant life sectors, such as horticulture.

ClimatVeg should therefore lead to a number of recommendations for farmers, through some collaborative scenarios with farmers, the choice of crops grown, agronomic or irrigation practices: reducing water consumption for certain crops, using alternative ones, etc. All of which should improve the efficiency of irrigation and farming practices. As Valérie Héquet points out: "It is a complex subject that has not yet been undertaken." A highly topical issue.