Nitrogen Use of Almonds

David Doll, Farm Advisor, UCCE Merced

Nitrogen is considered a major or essential element of plant growth.It is necessary for proper leaf development, fruit development and growth, and to renew and invigorate fruit wood. As trees come into production, their need for nitrogen increases due to the physiological processes involved in fruit development, foliage formation, and the formation of tree reserves. Meeting the tree’s demand for nitrogen during these processes is critical since a shortage of this element can reduce yields.

Previous research has shown that most of the nitrogen applied to an orchard becomes part of the hull, shell, and kernel. Therefore, by estimating the crop load of the coming growing season, we can determine the tree’s need for nitrogen. The nitrogen used in the almond crop (hulls, shells, and kernals) is about equivalent to 5% of the kernal pounds per acre yield. For example, a 3000 kernal pound yield uses about 150 pounds of nitrogen. Applications of just 150 pounds, however, will not replace the nitrogen lost to the crop due to inefficiencies of nitrogen delivery. Generally speaking, multi-application fertigation programs are the most efficient (around 80%), while one, large broadcast application is least efficient (around 50%). Tips for increasing efficiency will be included in another entry.

To help estimate nitrogen needs and budget, a new nutrient model has been developed at UC Davis by Dr. Patrick Brown and colleagues. This model, taking into account yields, July leaf sample analysis, and point sources of nitrogen which include manure, nitrate in the groundwater, and soil, can predict the needed amount of nitrogen needed for the coming year. Nitrogen application rate estimates are based on reaching the optimal levels of leaf nitrogen content (2.2-2.5%). Furthermore, annual potassium applications applied can also be calculated. This model can be found here.