Comparative evaluation of DRIS, DOP, and CND methods for nutrient diagnosis in melon (Cucumis melo L.)

Abstract On calcareous arid soils, high pH, carbonate chemistry, and cation competition weaken the link between soil nutrient pools and plant uptake, so nutrient status is best assessed from plant tissue; yet tissue norms calibrated for these soils are scarce. This study evaluated three tissue-based diagnostic methods: the Diagnosis and Recommendation Integrated System (DRIS), Deviation from Optimum Percentage (DOP), and Compositional Nutrient Diagnosis (CND) for melon ( Cucumis melo L.) grown on calcareous soils (pH 8.0–8.6, CaCO 3 15–38%) across 106 commercial farms in Iran’s Sistan Plain. Micronutrient deficiencies were widespread (B on 65.1% of farms, Fe on 54.7%, Zn on 46.2%). Despite the calcareous parent material, Ca was deficient on 72.6% of farms and Mg on 60.4%, whereas N (60.4%) and K (46.2%) were in excess. The interaction-aware indices tracked yield more closely (DRIS Nutrient Balance Index r = − 0.473, R 2 = 22.4%; CND r 2 r = − 0.451, R 2 = 20.4%) than the single-nutrient ΣDOP (r = − 0.289, R 2 = 8.4%); both outperformed ΣDOP under Steiger’s test for dependent correlations ( P < 0.001) and discriminated high- from low-yielding farms more accurately (AUC 0.73–0.75 versus 0.65), while DRIS and CND did not differ from one another ( P = 0.52). This ranking remained unchanged after excluding influential farms and after applying MM-type robust regression. Both interaction-aware methods identified Ca as the dominant limitation: DRIS ranked it as the most limiting nutrient on 39.6% of farms, and CND as the largest contributor to compositional imbalance. The co-occurrence of micronutrient and Ca–Mg deficiencies with N and K excess points to imbalanced, N-focused fertilization as the main constraint. Rebalancing fertilization toward micronutrient and Ca supply and reducing N inputs are management options that require experimental validation. The norms established here provide a regional reference for melon nutrition on calcareous arid soils.