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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

Irrigation and cropping plans 

According to the 2006 Collective Scientific Expert Report Drought and Agriculture, adjustments to two factors make it possible for field crops to adapt to drought situations: irrigation and cropping plans. However, farmers must be able to plan ahead.

Planning ahead


In 2005 and 2006, ministerial alerts issued early in February and March allowed farmers to select more drought-resistant species, leading to an increase in sorghum and sunflower plots and a decrease in maize plots. An INRA study (an appendix to the 2006 Collective Expert Report) calculated the benefit of planning ahead for a “typical farmer” from France’s southwest region, who divides his production between maize monoculture, rotating hard wheat/sorghum and rotating hard wheat/sunflower crops. If the farmer receives information before mid-July, he can optimise his irrigation tactics and his profit loss remains below 15%. However, if he is unable to plan ahead for irrigation bans, this loss rises to 54%.


Short-term adaptation


Although droughts are likely to occur with increasing frequency, cropping plan adaptations to date appear to be short- rather than long-term. Even if total grain maize crops are decreasing, they still represent double the surface area of sorghum + sunflower + soya crops. In 2011, grain sorghum plots decreased by 13% compared to 2010 (source: Agreste Conjoncture, September 2011). This situation can be explained by the fact that other factors influence farmers’ decisions, affecting a change in mentality. These include technical issues, such as a lack of productivity (for sunflowers) or weeds (for sorghum), and economic issues, such as changes in prices and aid payments under the Common Agricultural Policy (oilseeds) or structuring the industry (sorghum). The solution lies in diversification, which gives farmers more flexibility to adjust their production. The idea is to combine rain-fed and irrigated crop systems across a catchment area depending on available resources (watercourses and groundwater). One requirement would be to set up a database identifying viable crop systems for each pedoclimatic context. Despite the setup costs involved, this would make negotiations possible between different players using water resources on the territorial scale.


Maize or sorghum?


Software developed by INRA and Arvalis-Institut du Végétal makes it possible to identify the best cropping plan in line with irrigation quotas. Named LORA, it uses the rates at which plants’ water requirements are satisfied to calculate farms’ profit margins depending on irrigation options and labour. If, for example, irrigation quotas are reduced from 15 to 30%, replacing maize by sorghum, sunflower or straw cereal is only profitable for farms that originally had a small quota. With bigger quotas, maize crops combined with water rationing are more profitable. If restrictions become more frequent, the proportion of irrigated spring crops must increase (study completed in Poitou-Charentes in 2006 by Arvalis-Institut du Végétal).

Stricter water restrictions in the future could make it more profitable to replace maize by other crops such as sorghum or sunflower. © CHARTIER Michel
Stricter water restrictions in the future could make it more profitable to replace maize by other crops such as sorghum or sunflower. © CHARTIER Michel