Postharvest in California marks a new cycle in the Golden State’s tree nut industry, a time for cleaning trees and orchard floors after a robust harvest season, and a good time for planning as the after season quickly advances into the new calendar year.
Starting the year on the right foot involves many tasks and challenges. A clean orchard may be the first major task growers begin to address following the harvest and few are willing to argue that cleaning up mummy nuts and orchard floors represents a major objective for several weeks to come.
It’s also a time inspecting equipment, making repairs, adjustments and even adding to tool inventories in anticipation of the coming season.
Examining the annual pest management and control plan also represents an important time for planning for the new year and irrigation and water management is high on the list as well.
And what task could be more important than soil nutrients, health and fertility?
It’s all part of the recipe of formulation of just the right orchard plan, and let’s face it, no one does it better than the well deserving and hard working California tree nut farmer.
In a perfect growing world
Perfect weather rarely happens. When it comes to weed management, well thought out and generous weed management plans are often thwarted by rains that come early or late, or not at all. An unexpected disaster can strike a field or orchard almost without warning, and a dozen other unexpected issues can develop that can ruin those well made plans.
That’s why when planning for our new crop year we have learned to be flexible, to adapt to the circumstances as they change, to tolerate the ever-changing environment of farming. Even so, it should never stop us from making the effort to create the perfect plan as possible, and this is particularly true when we’re talking about applications of nutrients in our orchards. When growing food and fiber, it all starts from the ground up, so soil becomes our first stepping stone; our first building block to success or failure. Now that the winter rains have arrived, tree nut growers have already made their first application of nutrients.
Nitrogen demand & fertilizer response determined by environment
In a Pomology Department University of California, Davis, PowerPoint presentation titled Almond Nitrogen Nutrition using the Internet Based Fertilization Program, Patrick Brown, Steve Weinbaum and Forbod Youssefi, suggest for all nutrients the environment in which the tree is growing must be considered. They indicate this may be the result of changing soil conditions that limit the availability of a nutrient.
For the micronutrients (Mn, Cu, Fe, Zn, B) this might imply that special measures are needed to correct the deficiencies in the poor producing parts of the orchard. Soil and plant sampling should be performed. For the macronutrients (N, K, S) it is unusual for soil type to dramatically alter the availability of these nutrients hence it is unlikely that the poor performance is a result of a macronutrient deficiency.
For the macronutrients, N, K, Ca, P, S, and Mg yield is the most important determinant to nutrient demand. This demand occurs both at a whole field level (total yield) and may also occur locally at the branch level as indicated by the nutrient deficiencies surrounding a large cluster of Pistachio nuts.
Dormancy Application of Nutrients in Pistachio
Fertilizer to young trees is best applied in mid-spring and early summer. Late applications after August can encourage excessive vegetative growth and delay dormancy, which in turn increases the risk of frost damage.
Little is known about the effects of different fertilizer types on young pistachio trees. For almonds, Brent Holtz recommends using granular fertilizers for first-leaf trees, because the risk of root burn is increased with liquid fertilizers, as their application may result in high concentrations in the root zone.
N Soil Analysis
Soil nitrate analyses are far less common in orchards than in annual crops. However, soil sampling to determine nitrate-N levels in the root zone provides support for nutrient management decisions.
Nitrate-N present after leaf-out contributes to the tree’s N nutrition. One ppm of NO3-N in one foot of soil corresponds roughly to 3.5 to 4 lbs. N/acre. For example, a NO3-N concentration of 5 ppm in the top foot of the profile corresponds to 17.5-20 lbs. N/acre. In contrast, nitrate in the soil profile in fall is prone to leaching during the winter, especially in sandy soils with a low water holding capacity. High concentrations may be the result of N fertilizer applications in excess of tree demand.
P Soil Sampling and Analysis
Soil samples for nutrient analysis should be taken from the main root zone. Pistachio trees have an extensive root system with a taproot which allows them to extract water and nutrients from deep soil layers. However, most of the water and nutrients are taken up from the top 2 feet of the profile; especially in orchards with small bu.
K Fertilization of Young Trees
Little information is available about the K demand of young pistachio trees. A soil test before orchard establishment combined with annual leaf analyses help determine whether K fertilization is needed.
In areas where soils are known to fix K, such as the east side of the San Joaquin Valley, analyzing the soil for its K fixation capacity before the orchard is planted helps planning the K fertilization program.
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