Drought and salinity tolerances of young Jatropha
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Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
Int. Agrophys. 2010, 24(2): 121-127
Jatropha (Jatropha curcas L.) is receiving attention recently as a biofuel crop. It has been introduced as drought resistant, but few quantitative data concerning its tolerance have been presented. We evaluated the tolerances of Jatropha 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 five columns with one plant each: three were under stresses, the others provided potential transpiration. Three TDR probes were inserted into each of the two columns 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 minimising 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 Jatropha is not more tolerant either to drought or to salinity compared to other major crop such as soybean or wheat.
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