Évaluation des impacts de la sécheresse sur le rendement des grandes cultures en France

Abstract

The aim of the study was to estimate the impact of major drought events faced by French agriculture on yield, especially in 1976, 2003, 2005 and 2006. Estimations were made at the national and regional level for several crops. The statistics provided by the Service central des enquêtes et études statistiques (SCEES) of the Ministry of Agriculture were used. Yield increase over time was estimated using linear regressions of yield with harvest year. Yield deficits due to drought were calculated as the difference between actual yield and this regression. Our estimations of yield deficits at the national level quantify to what extent drought was damaging in 1976, 2003 and 2006. Deficits were less severe in 2005. Our results show that early-sown winter crops (rapeseed, barley) were less affected by drought than wheat (7 to 18% crop losses) and maize (7 to 23% crop losses) which is often irrigated but under irrigation restrictions. The sorghum crop, which is rarely irrigated, was the most affected because of severe pedoclimatic conditions. Sunflower was less affected than sorghum during the recent droughts. At the regional level, in 1976, drought was the most detrimental in northern France, whereas in 2003, drought severity was greatest in southern France. Our method allows estimations at the national or regional level. However, as the calculations were carried out using a difference in relation to a trend, they provide a lower value than results based on potential production or full irrigation. On the other hand, the effects of crop characteristics, environment and cropping system are combined in the estimation of loss for a crop and a region. Therefore, our estimations may reveal sensitivity to drought which are different from those provided by ecophysiological studies.