Role of controlled and slow release fertilizers in fruit crop nutrition

Abstract Fruit crops represent a wide range of woody perennial species cultivated in orchards where soils vary greatly in their biological, chemical, and physical properties. Production of high-yield and high-quality fruits requires the application of appropriate fertilizers. Conventional chemical fertilizers usually cannot sustain a long-lasting supply of nutrients and are often associated with nutrient loss, particularly nitrate nitrogen (N3O-N) leaching, ammonia (NH3) volatilization, and N2O emission, which may potentially contaminate natural aquifers and contribute to greenhouse gas omission. Controlled- and slow-release fertilizers (CRFs and SRFs) are those with nutrient elements coated or encapsulated, allowing nutrients to be released in either a controlled or slow fashion. Evidence suggests that CRF and SRF application not only enhances fruit crop yield and fruit quality but also reduces N3O-N leaching, NH3 volatilization, and N2O emission. Additionally, CRFs or SRFs can also improve rhizosphere microbial compositions and reduce detrimental effects of soil-borne pathogens. Recent studies further show that the application of CRFs or SRFs can alleviate Huanglongbing, a serious disease in citrus crops. Although CRFs or SRFs are expensive, the overall benefits of using CRFs or SRFs are well worth consideration in fruit crop production compared with the use of conventional fertilizers. While there are different types of CRFs and SRFs with different compositions and longevities on the market, fruit crops differ significantly in their growth and development and in nutrient requirements. There is a need for designing and developing new CRFs and SRFs that are sustainable and economically affordable for the production of fruit crops.