DEVELOPMENT OF DRIS NORMS FOR POTATO IN THE CALCAREOUS SOILS OF IRAN

The Diagnosis and Recommendation Integrated System (DRIS) has been pro posed to determine nutrient balance in plants at different stages of g rowth. The DRIS index for each nutrient-allows ranking of nutrients in order of their deficiency. Preliminary DRIS norms for potato (Solanum tuberosum L.) were developed during the 1991 growing season in Damava nd area located 70 km. northeast of Tehran. The soil and leaf samples at flowering stage (early tuber development stage) were collected from 50 different farms. Average concentrations of nutrients in both high- and low-yielding populations were calculated. The following average f oliar nutrient concentration were obtained from the high-yielding popu lations: N = 5.22, P = 0.38, K = 4.20, Ca = 1.50, and Mg = 0.65 percen t; and Fe = 150, Mn = 50, Zn = 40, Cu = 11, and B = 38 ppm. The averag e nutrient concentrations for the low-yielding population were close t o those in high-yielding ones except for K which was 3.23 in contrast to 4.20 percent. There was no significant relationship between differe nt soil nutrient availability indices and yield except for K. The DRIS indices ranked K as the most limiting nutrient in the low yielding fa rms with only one exception. It seems high rates of N and P fertilizat ion have created a lack of balance between these nutrients and K.