The cumulative effects of drought and lack of water take place "during pollination" of corn, a crucial period when corn is formed, explains Xavier de Castelbajac, cereal marketing manager at Maïsadour, a cooperative group which has 70,000 hectares of corn. in France.
Corn is generally sown between April and May, "the plants will grow and at the beginning of July comes the pollination period", then the flower "will fertilize the plant and thanks to this fertilization an ear will form with grains of corn", before being harvested in early October, explains Xavier de Castelbajac,
The group, of which 60% of the plots are irrigated, notes a clear difference compared to those which are not: the drop in yield is estimated between 10 and 20% for some against a drop of 50%, "even" more ", without irrigation.
Nationally, the proportion of grain corn plots considered to be in "good to excellent" condition rose from 75% to 68% in one week, according to the latest CéréObs barometer from FranceAgriMer published on July 29.
The drought and the succession of three heat waves, directly attributed by the scientific consensus to climate change, have severely reduced the flows of rivers in many regions, multiplying the measures to restrict water, sometimes concerning uses agricultural.
In France, out of an annual volume of water consumed estimated at 5.3 billion cubic meters per year, agriculture is the primary water-consuming activity (i.e. withdrawn and not returned to aquatic environments) with 45% of the total water consumed, ahead of the cooling of power plants (31%), drinking water (21%) and industrial uses (3%), according to the Ministry of Agriculture.
- "Nothing more to do" -
Faced with the drought of the soil, "irrigation is the only way to guarantee yield levels for corn. Behind it, sectors are counting on us", especially for animal feed, of which corn is one of the main components. , argues Xavier de Castelbajac.
But "what is problematic in relation to this use is that this consumption takes place specifically during a period when the resource is very little available", underlines Éric Sauquet, director of research in hydrology at the National Research Institute for Agriculture. , food and the environment (Inrae).
"Hydrological drought is the consequence, in general, of a deficit of rain observed either in the preceding days or in the months before, and the phenomenon of groundwater recharge has not taken place", but usually it is "this stock accumulated in winter which will provide support during the summer period when the water course is weak", explains the researcher
This year, "the very short-term response for corn that has already been sown is that there is nothing more to do," says Christian Huyghe, Scientific Director of Agriculture at Inrae.
- A barrier to adaptation -
The National Federation of Farmers' Unions (FNSEA) is advocating for better water storage with reservoirs, filled with surface water and runoff.
"France is 28 million hectares of useful agricultural area (SAU) and 1.7 million hectares are irrigated, therefore 5% of the SAU", sums up Christian Huygue.
But "the impact of these reservoirs on natural environments, certainly not neutral, still questions scientists", underlines Éric Sauquet.
Considered as "an obstacle to adaptation to global warming", betting on hill reservoirs (water storage) and water retention basins to guarantee agricultural yields, "is to give the illusion that the system can continue while there will certainly be other blockages at one time or another", when "we know that the size of the cake will decrease", explains the researcher.
If water storage and irrigation are considered one of the levers to protect agriculture, "others exist" however, say the researchers: rethinking the production system, changing crops, making polyculture, or even agroecology.