Using slow-release fertilizer is one of the sustainable strategies to improve the effectiveness of fertilizers and mitigate the environmental pollution caused by excess usage of fertilizer. In this study, a slow-release urea fertilizer with water retention and photosensitivity properties was prepared by a two-step method. It was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and an infrared camera. This fertilizer can prolong the release period of urea, improve water-retention capacity of soil, and carry out photothermal conversion under illumination. Comparing four release kinetics models, the Ritger–Peppas model was the best fitting model for releasing behavior in soil, and diffusion followed the Fickian mechanism. The application of fertilizer on winter wheat was carried out to intuitively evaluate the fertilizer’s effects on promoting plant growth and resisting water stress. Thus, this study provides a new strategy for improving fertilizer utilization rate and maintaining soil moisture, which will be beneficial for sustainable agriculture.

Fertilizers that release nutrients slowly can provide crops with consistent nutrients, while soils with good water-holding capacity can alleviate the impact of droughts on crops. Sodium alginate/carboxymethyl starch sodium/polydopamine/urea (SCPU) is a new kind of slow-release fertilizer with water absorption property. In this study, the Box–Behnken response surface methodology (RSM) was used to reveal the effects of concentrations of sodium alginate, carboxymethyl starch sodium, urea, calcium chloride and dopamine on the encapsulation efficiency and water absorption of SCPU. The results show that the optimum preparation conditions to obtain the highest level of encapsulation efficiency (89.27%) and water absorption (167.05%) are 2.2% sodium alginate, 5% carboxymethyl starch sodium, 30% urea, 1.9% calcium chloride and 0.52% dopamine.