Accurate nitrogen budgeting important for almonds

Accurate nitrogen budgeting important for almonds

The grower’s goal - without knowing exactly how much N might be lost or otherwise unavailable - is to apply enough nitrogen to ensure the trees are adequately supplied when needed.   The 4Rs of Nutrient Management philosophy: applying N at the right rate, at the right time, in the right place, and using the right source. 

Part of what makes almonds so desirable to consumers - aside from the great taste and crunch - is their high protein content. Ensuring good human nutrition means ensuring a strong tree nutrition plan is in place.

With almond bloom under way, almond growers should remember to utilize the nitrogen budgeting tool available at www.almonds.com/NitrogenBudgeting when making their plans.

While nitrogen (N) in the form of protein is desirable, many forms of nitrogen can be a serious problem in the environment. Ammonia and nitrate, the forms applied for plant uptake, can leach into surface water and groundwater, contribute to PM2.5 formation, and be converted to nitrous oxide (N2O), a potent greenhouse gas.

Moreover, there is a lot of fossil fuel energy hidden in nitrogen fertilizer production. Despite current cheap oil prices, the N fertilizer costs are substantial in almonds.

At the same time, plants are highly sensitive to too little nitrogen, leading quickly to decline in production. The uncertainty a grower is trying to manage is that some of the N applied is taken up by the microflora in the soil or converted by microbes to plant-unavailable forms of nitrogen (N2, N2O, etc.).

The grower’s goal - without knowing exactly how much N might be lost or otherwise unavailable - is to apply enough nitrogen to ensure the trees are adequately supplied when needed. 

Nitrogen management plans

With a better understanding of when exactly the tree takes up nitrogen, as well as what the nitrogen demand of the tree is, improved N efficiency can be achieved. This is the goal of the 4Rs of Nutrient Management philosophy: applying N at the right rate, at the right time, in the right place, and using the right source. A nitrogen management plan is a tool to help achieve the goals of the 4Rs.

Carefully planning N and other nutrient inputs, which does require putting a pen to paper or fingers to a keyboard, can help growers improve yields, reduce input costs, meet regulatory requirements, and maintain environmental stewardship. Planning is accomplished by utilizing data from past yields, leaf sampling and future yield potential.

Leaching risk

Nitrate leaching, which degrades groundwater (drinking water) quality, occurs when water moves nitrates below the root zone before the plant roots (or soil microbes) have a chance to take up the nitrogen. It is more likely to occur when larger amounts of nitrogen and/or excess water are applied. Strong El Niño rains can abet leaching, depending on their timing relative to N applications. 

In order to prevent nitrate leaching, growers should spread out N applications, applying smaller amounts of N but at a greater frequency. This can reduce the risk of off-site movement plus allow for more efficient uptake of applications that are made when the trees are receptive (the right time).

With the hope that El Niño rains will continue into the spring, almond growers should delay applying nitrogen until the tree has leafed out. According to the results of a research study funded by the Almond Board of California and USDA, almond trees do not take up applied nutrients from the soil until leaves are present to support transpiration through the leaf system.

The research demonstrated that mature almond trees rely upon stored nitrogen to feed bloom and leaf-out activities rather than taking in N from the ground. Therefore, almond growers should wait until leaf-out occurs. Furthermore, premature N applications are more prone to leaching, especially with rainfall.

Nitrogen calculator

A tool to help determine the amount of nitrogen to apply (right amount) to almonds is the Almond Board’s online nitrogen budgeting calculator, available through the California Almond Sustainability Program (CASP) at www.SustainableAlmondGrowing.org.

The nitrogen budgeting calculator is a free online tool that provides private assessment of N needs to enable more efficient use of nitrogen and avoid off-site movement.

The beauty of the tool is that it can store the information entered, allowing a grower to recalculate demand during the growing season as better assessments of yield and/or April leaf sampling data or other changes in the orchard become available.

Growers enter information on orchard configuration and yields (past and estimated current), along with nitrogen credits from nitrate in irrigation water, cover crops, compost and other sources, as well as data from leaf sampling. Utilizing this information, the system provides a total N fertilizer recommendation along with recommended amounts by crop growth stage.

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In addition to refining the N demand based on tree needs, the nitrogen calculator can also help growers through the process of submitting a basic nitrogen management plan (NMP), which, under the revised Irrigated Lands Regulatory Program (ILRP), all growers on irrigated farmland in the Central Valley are required to complete and submit through their regional water quality coalition.

The almond nitrogen budgeting tool provides specific almond information that goes beyond the ILRP requirement.

Deadlines for initial management plans vary depending on the coalition, size of farm, and the vulnerability for N leaching of the operation.

This year also marks the start of reporting nitrogen applications from the previous year. Growers in the Sacramento Valley, San Joaquin County, East San Joaquin County, Westside San Joaquin River Watershed, and Westlands Watershed must report how much N they applied in 2015. The rest of the Central Valley growers will begin to report in 2017 or 2018, depending on the size and vulnerability of the farm.

Key deliverable deadlines and contact information for Central Valley coalitions can be found on the CURES Watershed Coalition pages at www.CuresWorks.org.

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