Calcareous soils are known for their nutritional disorders due to the insoluble form of iron that limits free Fe availability for crops. However, it is well established that organic fertilization improves the physicochemical and biological properties of the soil and can mitigate nutrient deficiency. According to this approach, a greenhouse experiment was conducted on four pearl millet genotypes cultivated on calcareous soil added with an increasing concentration of animal compost as a sustainable approach to mitigate lime-induced Fe deficiency and propose an organic farming system. Fe mobility in the soil-plant system, plant growth, chlorophyll, and photosynthesis were analyzed. All plants grown in calcareous soil developed specific iron deficiency symptoms, with varying intensities and dates of emergence depending on genotype. The addition of compost significantly improved iron availability in the calcareous soil, increased Fe uptake and accumulation in the plant, alleviated symptoms of iron chlorosis, and stimulated photosynthesis and plant growth. Animal compost improved calcareous soil characteristics, followed by Fe availability and uptake. The genotypic differences observed in this study confirmed the specific performance of IP19586 and IP13150, which expressed higher capacities of Fe remobilization in the rhizosphere, Fe uptake, and preferential allocation to shoots.
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