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Drought and Agriculture: how can we adapt plants to lack of water?

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Climate change is a reality that affects the yield of all crops in temperate zones, Rethinking agricultural practices

Farmers have already changed the planting dates, with earlier planting in all field crops. This is a risk in case of late frost, but it allows for example wheat harvests before the droughts of early summer, while reducing the need for irrigation.

Planting according to the seasons (winter sowing / summer sowing) or crop rotations (somewhat neglected in recent years) can also modify the soil and more effectively mobilize the soil’s water reserves. For example, introducing a fallow makes it possible to store and conserve water. The practice of direct sowing with mulch also helps to save water by avoiding sowing irrigations. Planting density or nitrogen supply can also be growth “boosters” which can compensate for subsequent losses.

In addition, sensitivity to water stress will not have the same consequences if the species is cultivated for grains (fragile) or for vegetative organs (which can start again when conditions become favorable again).

More drastically, it can be envisaged to abandon one crop in favor of others, for example corn for sorghum or sunflower which have deeper roots and which are more resistant to drought.

Short term and long term

For the very short term, it is possible to install equipment that protects from the sun and allows better management of irrigation. On a small scale, a start-up like Ombrea offers intelligent shade houses for species with high added value, such as market gardening, horticulture, arboriculture and viticulture. On a larger scale, technical institutes such as Arvalis-Institut du végétal have developed, as part of the Phenofield project , eight mobile greenhouses, or “rolling umbrellas”, which cover a total of 5,000 m². 500 micro-plots of corn, wheat and other field crops are thus observed to better understand adaptation to water stress.

Already, rainwater retention basins are set up to store winter water, not without encountering administrative problems and certain societal resistance . Irrigation systems are also being refined, with “intelligent” drip, controlled by sensors. But these solutions are expensive because they are very technical. They will therefore not be accessible to the majority of farmers and crops.

Offer early or drought tolerant varieties

To dodge or to adapt to the lack of water, varietal improvement already provides solutions. For example, by selecting suitable varieties compatible with early sowing, corn farmers have advanced the fodder corn cycle and its harvest by more than a month since the 1980s. It is possible to choose earlier varieties for all crops , or to find new ones that are better suited.

Biodiversity and genetics: a winning duo

The selection and improvement of plants was done mainly on the criteria of productivity and nutritional quality. These were the priority post-war objectives. Today, awareness of the effects of climate change is accelerating the search for better resilience of crops to drought, in particular by re-evaluating wild plants or varieties from other regions which are more resistant to the lack of water.

Because the efficiency of water use is very different depending on the species . Tropical species, for example, have more efficient photosynthesis systems than temperate species and avoid keeping the stomata open and therefore water loss. It is therefore an interesting model to “import” into plants in temperate zones. But easier said than done …

Test many varieties for different criteria

Because adapting to drought is complex. It involves many metabolic pathways and “genetic” strategies on a single gene are not always satisfactory. This is why many research works rather focus on a “multi-factorial” improvement in drought. It consists in comparing the variations of the characters obtained in the field under different stresses and the variations of the genome , to search for the best candidate plants. The traits sought are, for example, the growth of leaves and reproductive organs, the rate of grain abortion, but also the architecture of the root system and the efficiency of water use (transpiration / biomass ratio produced ).

Simulate the behavior of plants by computer

In the European DROPS framework, with which INRA (the National Agronomic Research Institute) is associated, researchers are testing a large number of plants (corn, common wheat and durum wheat) to simulate the behavior of plants under water stress by computer. , and select those that should enter a varietal improvement program.

Intelligence and collective efforts

But it takes a decade for breeders to offer farmers the plants best suited to their constraints. However, if drought resistance becomes a major issue that is already perceptible, even in our climates, the solutions are not obvious. Despite new perspectives offered by biotechnology, genetics alone will certainly not answer them. It will have to be associated with new cultural practices (rotations, sowing dates, choice of early varieties , plot cover, intermediate crops, etc.), or even with different crop choices. We are already talking about the majority of vines and corn north of the Loire! Science fiction scenario? No, a prospective INRA study!

In any case, with the scarcity of water, farmers, but also all industrial players, will quickly have to work together, to produce with a minimum of water, and at the right time! And the technical solutions are being prepared now.

and even food security in some already fragile areas of the planet. It forces researchers and farmers to find new solutions to bypass the effects of drought now and above all to propose lasting solutions.

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