Use of the Diagnosis and Recommendation Integrated System (DRIS) for Determining the Nutritional Balance of Durian Cultivated in the Vietnamese Mekong Delta

Durian is one of the most valuable and expensive fruits in Vietnam and Southeast Asia. Leaf nutritional disorders are considered to be causes of reductions in fruit yield and quality. However, studies on the nutritional balance in durian leaf are limited. In this study, we used the DRIS method for leaf limitation nutrient diagnosis at the stage 2 months before durian flowering. Our objectives were to (i) establish DRIS norms for the macronutrients (N, P, K, Ca, Mg, and S) in durian leaf and (ii) determine nutrient value ranges that are insufficient or excessive in durian production. A total of 180 leaf samples were collected and examined from 90 durian orchards cultivated on alluvial soils in the Vietnamese Mekong Delta. The results indicate that DRIS establishment for durian was highly reliable due to the significant positive correlation (r > 0.5) among nutrient indices. The limiting nutrients in durian leaf at the investigation stage were S, Mg, Ca, and P, where S and Mg were the most deficient. The optimal ranges of nutrients in durian leaf were determined and recommended in this study. Further studies are necessary to validate the efficiency of DRIS using nutrient omission trials under durian cultivation.