Determination of DRIS reference norms for autumn sugar beet in Khuzestan province

Plant analysis is successfully used in monitoring nutritional status, recommending fertilizer rates and types, and maximizing fertilizer efficiency in sugar beet. Diagnosis and recommendation integrated system (DRIS) is a comprehensive approach which does not have limitations of the critical value approach (CVA) and sufficiency range approach (SRA). Over- dose application of fertilizer increases root yield but decreases crop quality. In this investigation, the amount of nutrients in leaf samples and yields from 383 fields throughout Khuzestan province were determined for three years. Then, database containing 5500 data including yields and concentration of nutrients was made. According to the DRIS method, the whole sampled fields were divided into two low and high yielding populations based on root yield of 53 tha- and white sugar yield 6.3 tha. Then, all forms of expression were determined in each sub-population and the variance was calculated. In order to select the best reference norms, the largest variance ratio (SB/SA) was taken into account. Finally, 55 reference norms were selected. DRIS indices were calculated using Excel software. Mean concentration of NO3-N, N, P, K, S was 0.89, 3.98, 0.7, 3.6, 0.5 percentage and for Mn, Zn, Fe, Cu and B was 09, 34, 36, 6.5 and 40 mgkg-. In order to check the precision, accuracy and usefulness of the norms and indices, the results of two fertilizer experiment were evaluated. The results showed that these reference norms as well as the DRIS indices seems to be useful in determining nutritional status of sugar beet.