Efficient Use of Nitrogen in Almonds

Mario Viveros

UCCE Farm Advisor, Kern County

Deciduous Tree Fruits and Nuts

April 12, 2000

Nitrogen is an essential element of plant growth. In almond trees, nitrogen is needed to renew and invigorate fruiting wood. Also, it is needed for fruit growth and development. The greatest need for nitrogen occurs when the almond trees came into production. At this time, the demand for nitrogen is due to fruit development, foliage formation and tree storage in roots and branches. We must meet the tree demand for nitrogen, since a shortage of this element can reduce yields.

Most of the nitrogen applied to an almond orchard becomes part of the kernel, hull and shell. Therefore, the projected yield of the orchard can be used to estimate the need to replace nitrogen removed in the crop. Apply approximately 1/10 pound of actual nitrogen for each pound of projected Kernel (meat) yield. Example, if an orchard will yield a ton of meats, apply 200 pounds of actual nitrogen per acre. It is of great importance not to over-fertilize an almond orchard. Over-fertilization can lead to excessive vegetative growth which can create shading for fruiting wood. Furthermore, over-fertilization will increase production costs and will lead to grown water contamination.
Wilburn Reil, Farm Advisor in Yolo/Solano Counties suggest the following orchard cultural practices to maximize nitrogen efficiency and to minimize nitrogen losses.

Maximize Efficiency:
· Apply N only when leaves are present and the tree roots are active.
· Apply a uniform irrigation that is adequate to carry the N into but not past the root zone.
· Because young fruit trees have a fairly constant N uptake, apply multiple applications of N throughout the growing season.
· Mature trees need most of the N in early spring, therefore, a late summer application of part of the N before an irrigation will provide the tree with N for early spring growth. The rest of the N needed should be applied during the spring.
· Fertigation has generally been very efficient in N applications.
· Analyze leaves in July each year to fine tune N level to the orchard. Maintain the level in the adequate range.
Minimize Losses:
· If fertilizer is surface applied, disc or irrigate N into the root zone shortly after application.
· Fertilize the tree, not the covercrop. Evaluate how best to bypass the covercrop. This may be by applying the fertilizer to the herbicide sprayed strip, mowing, or cultivating the covercrop.
· Don't over irrigate. Nitrogen is soluble and moves with water. Excessive runoff of tail water or leaching will remove N.