Effect of Phosphorus Fertilizer Type on Micronutrient Nutrition of Wheat Under Mediterranean Drought Conditions

Micronutrient deficiency in crops is not only an agronomic problem but can also lead to severe health issues in humans with cereal-based diets. Phosphorus fertilization and drought stress exacerbate the problem. However, the effect of different P fertilizers obtained from recycling (biobased fertilizers, BBFs) on micronutrient uptake under water scarcity conditions remains poorly understood. A two-season field experiment under rainfed conditions in southern Spain was conducted to evaluate the effect of different P fertilizers on the Fe, Cu, Mn, and Zn nutrition of wheat. Micronutrient uptake and homeostasis varied depending on the fertilizer, which was not explained by the amounts supplied with fertilizers. In the first year, compost-type BBFs decreased the Fe concentration in grain by 20%, whereas fertilizers obtained by ashing increased it by 84.7% relative to superphosphate. Biobased fertilizers, except compost, decreased the P:Fe ratio by 48%, indicating increased Fe digestibility relative to superphosphate. Biobased fertilizers reduced the risk of P-Zn antagonism. Carbon-rich BBFs decreased the HI, affecting micronutrient remobilization. Severe drought during the second year led to no significant difference in the evaluated variables between BBFs. These results provide important insights into the impact of fertilizer type on micronutrient nutrition, with some showing positive effects on biofortification relative to soluble mineral fertilizers under drought conditions.