Nitrogen is the nutrient plants require in the largest quantity for better yield and quality. Nitrogen is also an integral constituent of proteins, nucleic acids, chlorophyll, co-enzymes, phytohormones,and secondary metabolites, and its deficiency can negatively affect yield. Nitrogen-deficient plants are stunted, with narrow, small, pale leaves. Excessive N application increases vegetative growth and susceptibility to diseases that infect fruit, kill spurs, and reduce yields in subsequent years. Managing nitrogen is critical to tree health and productivity, and active understanding of how it plays in the general horticulture of the tree is critical.

In response to evidence of nitrate pollution of groundwater in California, the various Regional Water Quality Control Boards have adopted regulatory programs to protect groundwater resources that requires growers to use best nitrogen (N) management practices to reduce nitrate loading. As a help to growers, this publication has been created to optimize N use efficiency in citrus and avocado crops with the outcome of reducing N leaching.