Drought and Salinity Tolerances of Canola.

Canola (Brassica napus.) has been widely cultivated for vegetable oil and is expected as a biofuel crop rencently. Few quantitative data concerning its tolerance have been presented. We evaluated the tolerances of Canola to drought and salinity stresses in terms of parameter values in the widely used macroscopic root water uptake model. With such parameter values, root water uptake under stresses can be accurately predicted, which may contribute to efficient water management in arid and semiarid regions where irrigation is required to attain high yield. We conducted a column experiment using nine columns with one or two plant each: three were under drought stresses, the another three were under saline stress and others provided potential transpiration. Two soil moisture and EC probes were inserted into each of the three columns under the stress to observe water content and electrical conductivity. The soil surface was covered to prevent evaporation. Weight of the columns was manually measured to obtain daily transpiration. After the stress period, root density distributions were obtained by dismantling the columns. Three parameter values were inversely determined by minimizing the sum of square differences between observed and calculated daily transpiration rates. Water uptake at each depth and time was calculated by substituting linearly interpolated matric and osmotic potentials into the stress response function. Optimized daily transpiration rates agreed well with the observations. Determined stress response functions indicate that Canola is not more tolerant to drought compared to other major crop such as soybean or wheat. On the other hand, it is found to be more tolerant to salinity stress than other major crops.