It should not be a surprise to anyone that crop nutrient prices are reaching record levels this year. A strategy for maintaining tree health and productivity and improving efficiency of nutrient use while watching input costs involves the familiar ‘spoon feeding’ method promoted by many crop advisors.
“Anytime the water goes on, something should be in it,” certified crop advisor Rich Kreps said. “Small shots over the growing season help with efficiency.”
The supply issue with crop nutrition is the result of a perfect storm, Kreps said. High prices last year for corn and soybeans created demand and, with supply lagging, growers are facing high costs for important nutrients.
Small shots of essential nutrients rather than huge slugs three times during the growing season improves their efficiency. Timing the applications with tree demand will also help lower the amounts needed.
“Match tree demand to improve efficiency and use 30% less NPK,” Kreps said.
The UC ANR Nutrient Management site shares that rapid N uptake coincides with the time of rapid biomass accumulation. When N supply is adequate, crop N uptake during vegetative growth is mainly determined by crop growth rate and is affected by nutrient availability and environmental conditions, such as water availability, temperature and solar radiation.
The N concentration in plant tissue (e.g., leaves and petioles) strongly depends on N availability. Tissue N concentrations can be used to determine critical and optimal N concentrations in specific plant parts at defined periods of growth. Timing and rates of fertilizer N applications can be optimized based on critical N values to increase N use efficiency and prevent N losses.
Macronutrients calcium, magnesium and sulfur are also needed in tree nut production, but less is required. These nutrients have symbiotic relationships; applying more than necessary or less of one can affect the efficiency or availability of others.
Kreps calls NPK along with calcium, magnesium and sulfur the “symbiotic 6,” using the example of a sulfur application which makes calcium more available.
Balancing NPK is important. Kreps said a strategy is to start heavy on P and then add N. The ratio of 3-1-2 comes later in the season after P and N have been adequate.
As for micronutrients important in tree nut production, Kreps said soil or leaf samples could determine critical needs.
Information on nutrient budgeting can be found on the UC ANR Nutrient Management Resource Center site. The Almond Board of California also has The Nutrient Management module of the California Almond Sustainability Program. It is designed as a grower practice self-assessment, but also contains information about nutrient management in almonds.
