Preparation and characterization of a CDs based hydrogel slow-release fertilizer

Low utilization rate of chemical fertilizers is a main limitation for improving crop yields. Peanut bran carbon dots (CDs) have been shown to boost Italian lettuce growth, while hydrophilic CDs can easily flow away with water during application, which leads to CDs wastage and water losing. Therefore, it is crucial to develop a material with slow-release capacity of nutrient elements and CDs along with water-retaining function. In this study, acrylic acid and acrylamide were reacted with urea, potassium phosphate and other materials, thus a hydrogel slow-release fertilizer was firstly designed. Then, peanut bran CDs were added into the hydrogels to prepare a novel CDs based hydrogel slow-release fertilizer (CDs-hydrogels). Experimental results show that the prepared CDs-hydrogels have high water retention capacity and element release capacity of N, P, K. Most importantly, the CDs within these hydrogels, via its changes in luminescence, the releasing rate of nutrient elements can be monitored.