Minimizing the consumption of agrochemicals, particularly nitrogen, is the ultimate goal for achieving sustainable agricultural production with low cost and high economic and environmental returns. The use of biopolymers instead of petroleum-based synthetic polymers for CRFs can significantly improve the sustainability of crop production since biopolymers are biodegradable and not harmful to soil quality. Lignin is one of the most abundant biopolymers that naturally exist.In this study, controlled-release fertilizers were developed using a biobased nanocomposite of lignin and bentonite clay mineral as a coating material for urea to increase nitrogen use efficiency. Five types of controlled-release urea (CRU) were prepared using two ratios of modified bentonite as well as techniques. The efficiency of the five controlled-release nano-urea (CRU) fertilizers in improving the growth of tomato plants was studied under field conditions. The CRU was applied to the tomato plants at three N levels representing 100, 50, and 25% of the recommended dose of conventional urea. The results showed that all CRU treatments at the three N levels significantly enhanced plant growth parameters, including plant height, number of leaves, fresh weight, and dry weight, compared to the control. Additionally, most CRU fertilizers increased total yield and fruit characteristics (weight, length, and diameter) compared to the control. Additionally, marketable yield was improved by CRU fertilizers. Fruit firmness and acidity of CRU treatments at 25 and 50% N levels were much higher than both the 100% CRU treatment and the control. The vitamin C values of all CRU treatments were lower than the control. Nitrogen uptake efficiencies (NUpE) of CRU treatments were 47–88%, which is significantly higher than that of the control (33%). In conclusion, all CRU treatments at an N level of 25% of the recommended dose showed better plant growth, yield, and fruit quality of tomatoes than the conventional fertilizer.

Crop production faces challenges in achieving high fertilizer use efficiency. To address this issue, slow-release fertilizers (SRFs) have emerged as effective solutions to minimize nutrient losses caused by leaching, runoff, and volatilization. In addition, replacing petroleum-based synthetic polymers with biopolymers for SRFs offers substantial benefits in terms of sustainability of crop production and soil quality preservation, as biopolymers are biodegradable and environmentally friendly. This study focuses on modifying a fabrication process to develop a bio-composite comprising biowaste lignin and low-cost montmorillonite clay mineral for encapsulating urea to create a controllable release fertilizer (CRU) with a prolonged nitrogen release function. CRUs containing high N contents of 20 to 30 wt.% were successfully and extensively characterized using X-Ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). The results showed that the releases of N from CRUs in water and soil extended to considerably long periods of 20 and 32 days, respectively. The significance of this research is the production of CRU beads that contain high N percentages and have a high soil residence period. These beads can enhance plant nitrogen utilization efficiency, reduce fertilizer consumption, and ultimately contribute to agricultural production.

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.