Synthesize of bio-based encapsulated nano urea modified hydroxyapatite for controlling release of nitrogen and enhancing green bean yield

The massive rise in the world population requires increasing food production, and the world needs to decrease agricultural inputs like agrochemicals to preserve natural resources. The low nutrient use efficiency of conventional fertilizers has always been a concern because of their impact on the environment, and they are considered a waste of natural resources, which is against sustainability goals. Their low efficiency is attributed to their high solubility and fast release into the soil. Controlled-release fertilizers (CRFs) can reduce nutrient loss, which increases their efficiency and controls environmental pollution. In this study, single- and double-layers coating of biopolymers were applied to encapsulate nano urea-modified hydroxyapatite to control nitrogen release in soil. Hydroxyapatite was synthesized using the wet chemical precipitation method and two different rodlike and mesoporous hydroxyapatites were obtained. Nano-hydroxyapatite that had been synthesized was mixed with urea in two different amounts: 4:1 and 8:1. Biopolymers were then added on top. The current CRF synthesis strategy focuses on using low-cost, widespread biorefinery materials to decrease the manufacturing cost of CRFs. The nitrogen release rate of the synthesized CRFs and commercial urea in water and soil was studied. In field experiments, the impact of CRFs on green bean growth and yield was studied. The results showed that both single and double-coated CRFs reduced the N release rate in the soil and increased the fertilizer's longevity to 24 days, compared to 6 days for conventional urea. The total yield of green beans increased by 48%-120% by applying 75% of the recommended dose compared with that obtained with the full dose of conventional urea (control). Also, applying double-coated CRFs at N level of 25% of the recommended dose gives a green bean yield equal to the control. The recommended treatment is SC-CRF prepared with C-HA applied at N rate of 75% to match the future increase in the required amount of food.