It is necessary to develop the slow and controlled release fertilizer continuously

The development of slow-release and controlled-release fertilizers is an important way to reduce fertilizer rates, improve their use efficiency, and play an important role in supporting the sustainable development of modern agriculture. This paper reviewed 32 years of research in the fertilizer field at the Institute of Plant Nutrition, Resources, and Environment, Beijing Academy of Agricultural and Forestry Sciences. The research process, team organization, product innovation, and fertilization service of different fertilizers from the laboratory to the field were introduced, and future research directions were analyzed and prospected. Since 1991, the institute has been researching and developing slow-release and controlled-release fertilizers. In the initial stage (1991–1998), zeolite- and resin-coated fertilizers were successively developed. During the rapid development stage (1999–2015), controlled-release fertilizer products gradually realized industrialization and drove the development of the industry. During the stable promotion period (2016–), attention has been paid to bio-based coated controlled-release fertilizers, and considerable progress has been made. Zeolite-coated urea is an inorganic fertilizer that uses natural zeolite as a coating agent. Their functional characteristics were investigated, and a series of fertilizer formulations and application techniques were developed. Resin-coated fertilizers are prepared by spraying a layer of semi-permeable or impermeable material onto the fertilizer surface to achieve a controlled release of nutrients. The production process of the polyolefin resin is divided into three parts: dissolution of the coating material in the solvent, granule coating, and solvent recovery. In 1998, the institute developed spouted-bed coating equipment with an annual output of 2000 t of resin-coated fertilizer. Thermosetting resin-coated fertilizer is another major type for which the solvent-free in situ reaction film-forming process is commonly used. A high-efficiency mixed spraying method with a self-cleaning function was proposed, and semiautomatic and continuous automatic production was developed one after another. Simultaneously, nutrient release prediction technology and online rapid detection technology were developed for controlled-release fertilizers, and a series of special formula fertilizers and their application technologies were developed. The innovation of slow-release and controlled-release fertilizers has served the precise nutrient requirements of crops from the field to horticulture and promoted upgrading the fertilizer industry, reducing the fertilizer rate, enhancing fertilizer use efficiency, and even controlling non-point source pollution. To meet the realistic need for agricultural development in the future, it is still necessary to continuously study biodegradable coating materials for fertilizer products, the multi-stage continuously controllable release of nutrients, innovative large-scale and continuous production processes, online rapid detection technologies for product quality, and special multi-component and controlled-release functional fertilizers for crops.