Phosphorus-zinc Interactions in the Soil Environment and their Effects on the Sustainability of Agricultural Soils

Phosphorus (P) and zinc (Zn) are essential nutrients required for plant growth and productivity. Phosphorus plays a pivotal role in energy transfer (ATP), nucleic acid synthesis, root development, and grain formation, while zinc is involved in enzyme activation, hormone synthesis, photosynthesis, and seed development. Calcareous soils, which dominate large areas of Iraq and the Middle East, pose significant challenges due to their high calcium carbonate content and alkaline pH. These conditions lead to phosphorus precipitation as insoluble calcium phosphates and zinc immobilization through adsorption or precipitation as carbonates and hydroxides, thereby reducing their availability and causing deficiency symptoms such as slow growth and purpling of leaves in P deficiency, or stunted plants and interveinal chlorosis in Zn deficiency. Nutrient interactions between P and Zn represent an additional challenge; excessive P fertilization often suppresses Zn uptake, while balanced fertilization enhances the utilization of both nutrients. The major processes governing phosphorus include mineralization, immobilization, adsorption–precipitation, and desorption, whereas zinc undergoes mineral weathering, adsorption onto soil minerals, precipitation, organic complexation, and redox reactions, all of which restrict their bioavailability, particularly in calcareous soils. Recent studies from Iraq, the broader Middle East, and global field trials have demonstrated that integrating nanofertilizers, foliar applications, and organic amendments (such as compost and vermicompost) within integrated nutrient management (INM) systems significantly improves the availability of phosphorus and zinc. These practices enhance the productivity of strategic crops such as wheat, barley, and maize. Linking these nutrient management strategies with the United Nations Sustainable Development Goals (SDGs)—particularly SDG 2 (Zero Hunger), SDG 3 (Good Health and Well-being) through zinc biofortification, and SDG 12 (Responsible Consumption and Production)—highlights the strategic importance of sustainable phosphorus and zinc management in calcareous soils.