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L'Unité Expérimentale de Gotheron développe des programmes d'expérimentation-recherche sur les systèmes de production durable en  ARBORICULTURE  fruitière (abricotiers, pêchers, pommiers, poiriers). © MAITRE Christophe

Water and agriculture

Combining drought-tolerant varieties and crop management 

The choice of the plant variety and the type of crop management depending on water availability is also a promising approach. The SUNFLO model, developed by researchers at the Joint Research Unit for Agrosystems and Territorial Development (AGIR), makes it possible to combine different phenological (length of the post-flowering phase), morphological (leaf surface area) and physiological traits (speed of stomatal closure), and test them in different pedoclimatic conditions over the long term.

In addition to plant tolerance, the entire crop system must be adapted to take into account uncertain water availability. Given this situation, the aim is to increase profitability over several years, rather than focusing on annual performance. This is a major challenge for research, which must find coherent strategies that rely on several interdependent factors: cropping plans, crop varieties and management.

 

Two possible strategies

The delaying strategy consists in advancing or delaying the most delicate stages of plant development (often flowering) to periods when water stress is less likely. Plant varieties that have short life cycles and/or are capable of being sown at earlier dates are used. However, this strategy has a drawback: shortening the life cycle negatively affects radiation interception and therefore potential yield in good years.

 

Another strategy is rationing, which can be achieved in two ways: by reducing plant transpiration or by reducing soil evaporation during the first part of the cycle to save water for the grain-filling phase. Each strategy suits different varieties and crop management techniques. To minimise transpiration, it is possible to select plant varieties that have fast stomatal closure or moderate leaf-area indices, and combine this with crop management techniques like low population density and reduced nitrate fertilisation. To minimise soil evaporation, soil should be covered quickly. In this situation, an early variety with a higher seedling density and sufficient fertilisation is more appropriate. To manage these different parameters and produce strategies and varieties that adapt to drought scenarios, researchers have developed dynamic models that “imitate” how plants operate depending on their characteristics and environment (climate, soil and crop management).

 

A model for sunflowers

Researchers model the characteristics of sunflower varieties to determine the best crop strategies given different drought scenarios. © CARRERAS Florence
Researchers model the characteristics of sunflower varieties to determine the best crop strategies given different drought scenarios. © CARRERAS Florence

The SUNFLO model, developed by researchers at the Joint Research Unit for Agrosystems and Territorial Development (AGIR), makes it possible to combine different phenological (length of the post-flowering phase), morphological (leaf surface area) and physiological traits (speed of stomatal closure), and test them in different pedoclimatic conditions over the long term. The model takes into account each variety’s characteristics using phenotyping data collected in fields and greenhouses. In this way, scientists have discovered the importance of early stomatal closure in environments where there are early and lengthy water constraints. Meanwhile, in more favourable environments, it is better to encourage radiation interception and photosynthesis. Not only will this tool lead to a guide to using plant varieties, it will also improve the varietal evaluation system. Virtual experiments will build on traditional multi-site and long-term tests, thus widening the range of pedoclimatic situations examined.

For more precision, researchers are currently working on links between crop practices and the development of the sunflower disease Phoma. This disease increases yield losses in dry conditions.