Nitrogen deficient highbush blueberry branches (right)
Nitrogen stress has a major impact on development of the whole plant, leading to poor growth, quality and health. Soil Nitrogen supply rarely matches plant demand, so supplementary feeding can have a major impact on plant performance. Nitrogen stress is often worse in compacted or alkaline soils, following cold, wet growing conditions and when plants experience high light intensity. Nitrogen is required for building the amino acids, genetic material and proteins that influence both structure and function of the entire plant.
Nitrogen regulates leaf and canopy development, influencing photosynthesis, growth rates and aging. Low Nitrogen status results in low leaf area, slow growth and early on-set of senescence. High Nitrogen status can lead to increased biotic stress and delayed maturity.
Low Nitrogen status is first seen in older leaves, as Nitrogen is pulled from chlorophyll to support new tissue development. Older leaves develop a uniform chlorosis, turning from green to bright yellow. Younger leaves are always darker green.
Applying a foliar treatment in response to visual symptoms can be very effective in maintaining growth and health, particularly during critical stages of development.