Abstract
Several studies have pointed out the promising use of nutritional diagnosis methods for the determination of optimum nutrient contents in plant tissues. The present investigation was carried out in different oases in Southern Tunisia to determine reference values for the interpretation of leaf analyses of date palm (Phoenix dactylifera) Deglet Nour cultivar with the Critical Value Approach (CVA) and the Compositional Nutrient Diagnosis (CND). A database (n = 100) of yield and mineral concentrations taken from date palm leaflets in October, at the maturity stage of dates, was used. The yield cut-off between low-yield and high-yield subpopulations, selected from cumulative variance ratio functions across survey data, was 76 kg palm−1 and the global nutrient imbalance index (CNDr2) was 10.06. Critical CND nutrient indices were found to be symmetrical around zero as follows: (1.59; +1.59) for IN, (−0.44, +0.44) for IP, (−0.63, +0.63) for IK, (−0.94, +0.94) for ICa, (−1.05, +1.05) for IMg, (−0.80, +0.80) for IFe, (−0.74, +0.74) for ICu, (−0.80, +0.80) for IB, (−0.93, +0.93) for IZn, (−1.04, +1.04) for IMn, and (−1.03, +1.03) for the residual value. Compared to CND, the CVA approach shows weak detection of the nutrients that cause nutritional imbalance. CND indices revealed, except for N, the presence of nutrient imbalances and the necessity to correct the mineral nutrition of date palm in the Kebeli oases.
Highlights
In Tunisia, date palms (Phoenix dactylifera) are an important part of Tunisian agriculture
The lower values of the sufficiency range are the minimal critical points, whereas the higher values are the toxic critical points. These two critical foliar concentration values correspond to Sufficiency intervals obtained with the critical value method are presented in Table 1 for all 90−95% of the maximum yield [32,33] on the yield envelope curve (Figure 1)
We developed compositional nutrient diagnosis norms for date palms (Phoenix dactylifera), the Deglet Nour cultivar in Kebeli oases in Southern Tunisia
Summary
In Tunisia, date palms (Phoenix dactylifera) are an important part of Tunisian agriculture. Tunisia is the world’s largest date exporter in value and accounts for 16% of the date world trade value [1]. Despite the importance of date palms, available information about the nutritional requirements of the different cultivars are lacking. Determination of the optimum levels of fertilizers could result in higher yield and better fruit quality that could increase farmers’ incomes. To improve fertilization and cultural practices, soil testing is a tool for assessing the amount of plant-available nutrients in the soil. Soil samples should be taken where the plant roots are concentrated and where
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