Series
4 episodes
Summer series: water seekers
His red hair and beard just emerge from the green of the miscanthus plants. The story of the arrival on his farm of this large herbaceous plant from Asia, Jérémy Ditner, a 38-year-old Alsatian farmer who grows around twenty varieties of cereals and vegetables in the town of Bernwiller (Haut-Rhin), tells it with pride. Because it is a family heirloom. “It was my father who had the idea,” explains Jérémy.
In the 2000s, the town’s catchment water flirted with the nitrate drinking standard, set at 50 mg per liter. On this large Sundgau plain, corn and wheat, the dominant crops in the area at that time, needed nitrogen fertilizer to grow. But, by dint of seeping into the soil, they contaminated the shallow aquifer.
Mathieu Ditner, Jérémy’s father, mayor of the village, understands the problem well because he is president of the Water Union. Since 1993, he himself had already been experimenting with the cultivation of miscanthus, a perennial plant which requires neither inputs nor irrigation and whose rhizomes do wonders for absorbing pollutants. He then had the idea, at the end of the 2000s, to suggest to his fellow farmers that they also cultivate them to protect the catchment. To convince them, he created an outlet, using it as fuel for the communal biomass boiler. Eight farmers then decided to get started. “After two or three years, the nitrate level was back down to between 25 and 30 mg,” says Jérémy.
After nitrates, pesticides
Today, miscanthus covers 35 hectares in the catchment supply zone. Including ten at Jérémy’s. Because, after an agricultural BTS and a master’s degree in agricultural business management, he took over the farm in 2014. With the desire to go even further than his father. “We had solved the nitrate problem but not that of pesticides. However, two thirds of my plots are located in the drinking water catchment area and I also have many along rivers, which gave me a responsibility with regard to water. »
In 2017, the farm gradually switched to organic. A minority choice in this large grain-producing region. “The trigger,” he continues, “may have been when my wife was pregnant. The doctors told us that it would be better to feed the baby organic food. It felt strange to tell myself that what I was producing wasn’t healthy enough for him. »
The organic approach leads to a whole series of changes. Far from the monoculture of corn, Jérémy opts for a wide diversity of cereals (soybeans, wheat, malting barley, fava beans, etc.) and vegetables (squash, potatoes, leeks, carrots, parsnips, etc.), which he does not irrigate.
“Transform floors into sponge”
To gradually do away with phytosanitary products, Jérémy Ditner, who has since become vice-president of Bio en Grand Est, uses lactic ferments which develop the natural fertility of the soil. “This increases organic matter and improves the water retention capacity of the soil. » The stakes are high in the region. “Here, there tends to be too much water in winter and not enough in summer,” explains Jérémy. A problem that is getting worse with global warming. In order to protect soil moisture, the cereal grower now also leaves a plant cover on his land between each crop.
To go even further, the farmer, municipal councilor and as such involved in the public establishment which manages the water of the Largue watershed, of which he became president in May 2026, also began planting hedges. Firstly along the streams which cross its plots. But also between the Krebsbach and the Spechbach, the two surrounding rivers. Dogwoods, hornbeams, wild cherry trees, birches, spindle trees… A three-kilometer green network has already been planted.
Ultimately, there is also the question of creating a pond, in order to create a wetland. “The goal is to transform the floors into sponge as much as possible, to absorb the excess when it rains and retain humidity when it is hot,” explains Jérémy Ditner.
29 milligrams of nitrates per liter
French groundwater contains on average 29 milligrams of nitrates per liter, according to the latest official report. This is above the target value of 25 mg/l. The level of groundwater contamination presents strong territorial disparities, with the northern half of France being the most exposed to this pollution. Furthermore, almost 50% of groundwater bodies see their total pesticide concentration exceed the quality threshold of 0.5 µg/l, with the northern half of the country also being the most concerned. Agriculture is the main cause of these two categories of pollution.
