Nothing will hold a young tree back more than lack of water and lack of nutrients.
Dean Rainham, Horticultural Consultant at AgFirst Nelson, was called to diagnose a block of stunted trees. Lack of water was not the issue and herbicide spray program was benign. Dean turned his attention to nutrition.
Symptoms were shoot growth slowing, pale green to yellowing small leaves and reddening on the edges of new leaves (fig 1). A leaf test confirmed the problem: Acute Nitrogen deficiency.
Regular Nitrogen applications are usually required to maximise young tree growth. The root zone is relatively small so little and often is best practice. Fertigation is a good option, otherwise every 3-4 weeks apply a N based fertiliser e.g. CAN.
AgFirst recommend weekly monitoring of shoot growth. This provides feedback on the impact of the climate and inputs (water, nutrition etc.) on tree growth. This monitoring gives an early lead on when growth is slowing and drives confidence in strategies that maintain and increase growth.
Monitor 20 shoots weekly in a block, recording the different stages of growth from active, slowing and terminated growth. Compare growth rates and the ratio between shoot types (fig 3).
Dean Rainham has over 20 years experience in the agriculture and horticulture agribusiness sectors. View his full profile for contact details.