Growing drought-tolerant species
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Growing species with low water requirements helps save water when water resources are at their lowest.
Presentation
The objective is to favor species intrinsically tolerant to water scarcity (sunflower, sorghum...) over species with high water demands during periods when water availability may be limited (corn...).
The tolerance to water scarcity of these species is linked to their root profile, allowing them to utilize water available in the deep soil horizons, and/or to adaptation mechanisms to water availability such as reduced vegetative growth in favor of filling for sunflower or osmotic adjustment for sorghum.
The crop cycle also influences its vulnerability to water stress: choosing early varieties helps both to reduce total water needs and to partially avoid periods when water availability is lower.
Example of implementation
Introducing drought-tolerant crops (sunflower, sorghum…) on part of the irrigable area helps secure the volume of water available for corn under restrictive conditions, without excessively penalizing the yield of these crops.
The choice of species planted is made at the crop scale but can be guided by reasoning at the rotation scale to take into account the volume of water available for irrigation.
Similarly, the choice of species planted is made at the plot scale but can be guided by reasoning at the crop rotation scale to consider the volume of water available for irrigation.
Application of the technique to...
All soil types : Choosing crops with low water requirements is particularly justified in soils with low available water capacity.
All climatic contexts : Choosing crops with low water requirements is particularly justified in years with low rainfall, which cannot be anticipated.
Effects on the sustainability of the cropping system
"Environmental" criteria
Effect on air quality : Greenhouse gas (GHG) emissions decrease. Choosing crops with low water requirements can help limit nitrous oxide emissions when it avoids or limits irrigation. However, the effect of these crops is neutral compared to a water-demanding crop grown rainfed.
Effect on water quality : Choosing crops with low water requirements can help limit nitrate leaching when it avoids or limits irrigation. Moreover, if the drought tolerance of crops is linked to a root system allowing better soil exploration, winter residual nitrate can be lower than after corn, for example. However, the effect of these crops is neutral compared to a water-demanding crop grown rainfed. And if drought tolerance is linked to a shorter cycle, winter residual nitrate can be higher than after corn.
Effect on fossil resource consumption : Choosing crops with low water requirements can help reduce fuel consumption related to water application when it avoids or limits irrigation. However, the effect of these crops is neutral compared to a water-demanding crop grown rainfed. Additionally, sorghum or sunflower do not require drying. Finally, crops cited as drought tolerant also require less nitrogen than corn; thus, the indirect energy consumption linked to nitrogen fertilizer production is reduced.
"Agronomic" criteria
Productivity : Under non-restrictive conditions, sunflower or sorghum have lower yield potential than corn, but under strongly restrictive conditions, their yield is not penalized and may be higher than corn under the same conditions.
Soil fertility : No effect (neutral).
Water stress : Introducing crops with low water requirements reduces the risk of water stress.
Functional Biodiversity : Introducing crops with low water requirements (sunflower, sorghum…) in rotations dominated by corn increases domestic plant biodiversity.
"Economic" criteria
Operating costs : Sorghum or sunflower involve lower operating costs than corn.
Mechanization costs : If choosing crops with low water requirements avoids or limits irrigation, it reduces mechanization costs related to it, especially if the irrigation equipment is amortized. However, the effect of these crops is neutral compared to a water-demanding crop grown rainfed.
Margin : Under non-restrictive conditions, corn generates a better margin than sunflower or sorghum due to higher yield potential. But under strongly restrictive conditions, sorghum and sunflower have an advantage over corn.
Fuel consumption : If choosing crops with low water requirements reduces or limits irrigation, it reduces fuel consumption related to it (pumping…). However, the effect of these crops is neutral compared to a water-demanding crop grown rainfed.
"Social" criteria
Working time : If choosing crops with low water requirements reduces or limits irrigation, it reduces the working time related to it. However, the effect of these crops is neutral compared to a water-demanding crop grown rainfed.
Observation time : No effect (neutral).
For more information
- What place for sorghum in irrigated system? - Lafeuille B. - La France agricole n°3353, p66-67, Press article, 2010.
- Drought and agriculture - Reducing agriculture's vulnerability to increased water scarcity risk - Amigues J.P., Debaeke P., Itier B., Lemaire G., Seguin B., Tardieu F., Thomas A. (INRA), 2006 - Collective scientific expertise (synthesis)
- Irrigation - Saving water without drying out the result - La France agricole n°3396, Press article, 2011.
Contacts
Marjorie Troussard - CA 85 - marjorie.troussard@vendee.chambagri.fr - La Roche sur Yon (85).
Grégory Véricel - INRA - gregory.vericel@toulouse.inra.fr - Toulouse (31).
Rémy Ballot - INRA - remy.ballot@grignon.inra.fr - Grignon (78).
Appendices
S'applique aux cultures suivantes
