1Ph.D student, Department of Soil Science, Tarbiat Modares Universit, Tehran, Iran.
2Department of Soil Science, Tarbiat Modares University, Tehran, Iran.
3Department of Soil Science, Shiraz University, Shiraz, Iran.
4Soil and Water Research Institute, Tehran, Iran.
Boron (B) is essential to growth at low concentrations and limits growth and yield when in excess. Little is known regarding plant response to excess B and salinity occurring simultaneously. In this study, two models of Leibig-Sprengel (LS) and Mitscherlich-Baule (MB), originally proposed to explain plant response to nutrients only, were modified to evaluate canola yield response to combined levels of B and salinity stresses. The water salinity treatments were consisted of non-saline water, 3, 6, 9 and 12 dS m-1. The B treatments were 0, 10, 20 and 30 mg kg-1 added to soil as H3BO3. It was revealed that modified LS model can satisfactorily predict canola dry matter yield. The calculated statistics: Maximum Error, Root Mean Square Error, Modeling Efficiency, Coefficient of Determination and Coefficient of Residual Mass, indicated that the estimated relative dry matter yield for soil B concentrations and salinity levels by modified LS model compared to modified MB model was closer to the measured relative yield. Therefore, the use of modified LS model for estimating canola relative yield in salinity and B stresses is recommended. The threshold value of salinity increased with higher B concentration and maximum dry matter yields decreased with increasing B concentration. Excess B was found to decrease dry matter yield of canola. This effect was inhibited when plants were exposed to simultaneous B and salinity stresses. Both irrigation water salinity and B concentration influenced water use efficiency (WUE) of plant, however, only B concenteration influenced canola yield in in the same manner.