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Investigation of nutritional status of common bean fields in Fars province using Compositional Nutrient Diagnosis (CND)
Abstract
Evaluating the nutritional status and diagnosing the fertilizer requirements of common bean (Phaseolus vulgaris) fields in Fars Province are critical for translating findings into actionable fertilizer recommendations. Various methods are employed to assess crop nutritional status, with the Compositional Nutrient Diagnosis (CND) method offering advantages over others due to its consideration of nutrient interactions. This study aimed to evaluate the nutritional, soil, and yield status of bean fields in Fars Province, identify production-limiting factors, and apply analytical indices such as Deviation from Optimum Percentage (DOP) and CND. Given the importance of understanding bean nutrition, the project was conducted over three years across bean fields in Fars Province. Annually, 30–35 fields were selected, and soil/leaf nutrient concentrations were analyzed. Laboratory data were used to interpret nutritional status, with optimal nutrient norms calculated using intermediate yield cutoffs. These norms were standardized and presented as nutrient indices. Analysis of nutrient indices in low-yielding fields revealed widespread nutrient imbalances, deficiencies, and excesses. Results showed an average bean yield of 2,422 kg ha⁻¹, with a wide range of 1,000–4,150 kg ha⁻¹ (SD: 720.45), reflecting significant heterogeneity in farm management. Soil nutrient deficiencies were identified as primary yield-limiting factors. Phosphorus (P) deficiency was observed in 95.18% of fields, particularly in alkaline soils with high fixation. Zinc (Zn) deficiency ranked second, affecting 79.52% of fields. Potassium (K) and manganese (Mn) deficiencies were noted in 7.23% and 12.05% of fields, respectively. Using the DOP index, the order of deficiency severity was N > Mn > K > P > Zn. The Nutritional Balance Index (NBI) exhibited an inverse relationship with yield: fields with NBI > 102.19 yielded <2,500 kg ha⁻¹, while those with NBI < 102.19 achieved >3,500 kg ha⁻¹. Through CND, only 15.84% of fields fell into the high-yield group (mean: 3,565.63 kg ha⁻¹), whereas 84.16% were categorized as low-yield (mean: 2,422 kg ha⁻¹). Reference values (V*X) for critical nutrient thresholds were established using high-yield group means. Macronutrients: V*N= 2.92%, V*P = 0.65%, V*K = 2.83%. Micronutrients: V*Zn = -4.15, V*Fe= -1.52, V*Cu = -5.09, V*Mn = -2.09, V*Rd = 6.44. Proposed critical thresholds for leaf nutrient concentrations include 2.82% N, 0.29% P, 2.62% K, 24.31 mg kg⁻¹ Zn, 366.13 mg kg⁻¹ Fe, 9.75 mg kg⁻¹ Cu, and 18.95 mg kg⁻¹ Mn. The study concludes that phosphorus and zinc deficiencies, coupled with nutrient imbalances, are the primary constraints limiting bean yields in Fars Province.
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