Determination of salt tolerance threshold, slope of yield reduction and leaching requirement for madders under field conditions

In Iran, vast amounts of saline lands, shortage of fresh water and secondary land salinization are major limiting factors for conventional crop production. Use of salt tolerant crops such as madders (Rubia tinctorum L.) for utilization of saline soil and water resources has been the subject of many studies. In order to study the effect of salt stress on yielding of madder roots, a factorial experiment was conducted in the form of complete randomized block design with three replicates at Sadooq Salinity Research Farm, Yazd, Iran. Treatments were two planting methods (seeding, root-cutting) and different salinity levels of irrigation water (2.5, 7, 14, 17 dS/m). Results showed that at low salinity levels madders gives higher yield when planted by root-cutting method. However, at high salinity levels there is no difference between the two methods. Results of the experiment also showed that salt tolerance threshold value of madders is about 4 dS/m and the slope of yield reduction is 3.2 percent, classifying it as a moderately salt tolerant crop.