Crop management systems for rainfed and irrigated sunflower (Helianthus annuus) in south-western France

Abstract

In the context of EEC agricultural policy, the efficient production of sunflower (Helianthus annuus L.) requires the development of a wider range of crop management schemes than were used previously. Five different management options were applied to sunflower over a period of 10 years (1984–94) on a deep silty clay soil at Auzeville, near Toulouse, south-western France, combining different levels of crop density, N fertilization and supplementary irrigation. The effectiveness of these practices was evaluated on the basis of grain yield, oil production, amount of disease infection, N leaching, soil water deficit and economic return, using both experimental values and simulations with the epic-phase model.Grain yield ranged from 1 t/ha (with severe disease incidence) to 4 t/ha (no diseases, full irrigation). There was no evidence of higher yield variability between years for low-input cropping systems managed without irrigation.In the deep soils of Auzeville, c.100 mm of irrigation, split into two or three applications around flowering, appeared to be a good strategy for maximizing irrigation efficiency. Limiting leaf area expansion under rainfed management, by reducing crop density and N fertilization, limited stem infection frequency by Phomopsis helianthi and delayed soil water depletion, thus maximizing grain yield. Oil concentration was generally higher under full irrigation, but high values were also observed under rainfed conditions provided that a suitable genotype was used. The annual amount of N leaching, simulated by epic-phase, ranged from 17 to 40 kg/ha depending on N amount and irrigation volume. Under the current conditions of the Common Agricultural Policy, low-input and rainfed management appeared to be the most profitable strategy for the deep soils of south-western France.