On a global scale, soils (apart from permafrost) store the equivalent of 2.6 times the amount of carbon found in the atmosphere in the form of organic matter. They also absorb around a quarter of the planet’s CO2 emissions. This storage takes place through the combined action of photosynthesis, which extracts carbon from the atmosphere, and the decomposition of plants, which transfer the carbon they contain to soil. However, most of this absorption is done by forests, with farmland still only playing a secondary role. Nonetheless, an ambitious farming policy could reverse the trend and offer a way of fighting climate change more effectively. A winning strategy that would “build up the soil nutrient bank and increase soil fertility,” according to the French Ministry of Agriculture. Mindful of the issues at stake, Veolia encourages farming practices that would increase soil carbon stocks, without significantly changing the production system.
SmartFertiReuse for responsible irrigation
Repurposing treated wastewater while optimizing field fertilization is the aim of the SmartFertiReuse project, which combines several concepts in one: Reuse, which gives the water from the wastewater treatment plant a quality compatible with irrigation criteria; Ferti, because it involves fertilizing and irrigating crops simultaneously; and Smart, due to a monitoring and control interface (sensors) to promote responsible farming. In collaboration with Veolia’s Research and Innovation division and Veolia Water, Sede is steering this demonstration project that brings together a number of laboratories (AgroParisTech, etc.), industrial partners (Bio-UV, the start-up Ecofilae, Polymem, etc.), and players from the farming world (FDSEA 65, Hautes-Pyrénées Chamber of Agriculture, etc.). Launched in 2018, having received a label from the Agri Sud-Ouest Innovation and Aqua-Valley clusters and been named an Interministerial Single Fund winner, it is aiming to carry out the first irrigation tests without fertilizers in 2020, then with fertilizers in 2021.
In practice, the module is installed at the outlet of the wastewater treatment plant and analyzes the treated water. The latter contains nitrogen and phosphorus, which are mineral fertilizers in small quantities. The module takes into account the amounts of these minerals in the water and adds additional nitrogen to deliver optimal water for irrigation. In the long term, this would make it possible to decrease water withdrawals from the natural environment while ensuring crop irrigation throughout the year, even during periods of drought.
“4 per 1000,” or carbon sequestration in agriculture
The international “4 per 1000, Soils for Food Security and Climate” initiative (cf. interview) was launched by France during COP21 in late 2015. The idea: a 4‰ annual rise in the amount of carbon in all soils worldwide would compensate for all human-related greenhouse gas emissions. Applied to the first 40 centimeters, the 4 per 1000 target corresponds to soil carbon storage of 3.4 Gt of CO2 per year, which would theoretically stop the current rise in the concentration of carbon in the atmosphere.
“As the leading company selling composts on the national market, with over a million metric tons sold in France today, Veolia is very much involved in this initiative,” states Paul-Antoine Sebbe, CEO of Sede Environnement, Veolia’s agronomic hub.
A sign of the general interest in carbon storage, the subject is being studied as part of the European Union’s Common Agricultural Policy (CAP) reform.However, carbon storage is also one of the key issues in food-related soil security.
“In our so-called developed countries, there is currently no threat, as the population is not lacking food in terms of quantity. However, requirements are becoming higher and higher in terms of quality,” adds Paul-Antoine Sebbe. “This is leading to a reduction in artificial inputs that guarantee a minimum yield even in poorly maintained soils… We therefore need to go back to one of the basics of farming: the agronomic potential of soil!”
Improving the organic matter content of these soils by using composts as well as simplified farming techniques will make it possible to ensure both the quantity and quality of food products in the future. This is the thinking behind the Soil Advisor® project, developed in close collaboration with INRA.
Soil Advisor®: the app that keeps soils healthy
To support farmers in adopting responsible, more soil-friendly practices, the Soil Advisor® app “has been designed so that they can optimize organic fertilizer and amendment input,” explains Maelenn Poitrenaud, Innovation and Development Manager at Sede.
Its strengths: taking into account the specific features of the land and crops as well as the farmer’s agronomic practices, suggesting optimal compost use, and predicting the soil carbon storage capacity.“Providing guidelines for use based on renowned agronomic models allows us to reassure the end users and contributes to the enhanced deployment of our offerings,” adds Paul-Antoine Sebbe. “ Developed in partnership with the University of Colorado and INRA, Soil Advisor® is currently the only tool on the market allowing farmers to optimize their organic fertilization strategy. It does so by incorporating the long-term effect of the compost and its impact on changes to soil organic matter and soil carbon storage.”
After five years’ R&D, the application was rolled out in 2019 to a test panel of farmers and farming advisors, and will be launched for routine use* as of 2020. “Initial feedback is extremely positive, as no steering tool of this kind currently exists. Farmers are also more aware of the benefits of using organic matter,” states Maelenn Poitrenaud. Beyond their impact on the climate, organic amendments and fertilizers are also less expensive than chemical fertilizers, offering stable yields and resilience to climate events (by increasing soil water storage capacity, they help phreatic groundwater function correctly, for instance).
For Sede, the next step is developing a probe — “Soil Diag.” Capable of measuring and diagnosing the properties of soil (carbon and organic matter, nutrients, potassium, etc.) in real time, it offers farmers a reliable diagnosis.
“Paired with the Soil Advisor® app, it will provide them with instant simulations!” enthuses Maelenn Poitrenaud.
24% of global soils are degraded to various degrees, including almost half of agricultural soils
1,500 billion metric tons of carbon in soil organic matter worldwide, over twice the carbon in atmospheric CO2
1.2 billion metric tons of carbon per year could be stored in agricultural soils (crops and grasslands), i.e. an annual storage rate of around 4 per 1000 compared to the surface soil horizon.
*Sources: IPCC, 2013 & 2014
*Il s’agit d’un passage à une échelle plus importante, de manière moins « expérimentale » puisque seuls quelques agriculteurs étaient jusque-là dans la boucle.