Faba bean productivity in saline-drought conditions
Résumé
The response of faba bean(Vicia faba L., variety ILB1814) was evaluated in a factorial salinity-drought experiment, combining three levels of salinity in the irrigation water (EC1.0,2.3and3.6dS/m) and two levels of plant water status during two successive cropping seasons.The two levels of plant water status were obtained by supplying irrigation when the pre-dawn leaf water potential of the control treatments attained values of −0.3 and −0.6 MPa. The experiment was designed to analyse the effects of soil salinity, the effects of drought (detected by the level of the plant water status) , and the combined effect of salinity and drough ton the plant-water relationships, nitrogen balance and crop productivity (for both grain and straw). Soil salinity levels equal to or higher than 6.5dSm−1 affected the plants by reducing the grain number but not the straw weight. Drought at flowering, early podding and grain-filling stages reduced both grain and straw yields. Moreover, yield reductions were associated with increasing soil salinity levels, confirming an interaction between the salinity and drought effects on faba bean productivity. Symbiotic nitrogen fixation, as evaluated by the nitrogen balance, was more affected by drought than by salinity, and it may explain the absence of any observed effects of salinity under drought conditions. The comparison of these results with those obtained in similar experiments on wheat and barley revealed that these cereals and faba bean have contrasting behaviours under saline-drought conditions.