Nitrogen Budgeting

NITROGEN BUDGETING

It is important to supply almond trees with as much nitrogen as they need at different stages of growth to optimize yields and quality. Almond trees need nitrogen to form proteins, which in turn form protein-dense nuts.

Research has shown that almonds can achieve nitrogen use efficiencies (NUEs) of more than 70%, making almonds among the most efficient nitrogen using crop1. Applying nitrogen fertilizers in amounts that exceed what the tree can take up, or at a time when no uptake can occur, is not only costly: nitrogen in the form of nitrates may then move through the soil beyond the root zone, potentially leaching into and contaminating groundwater.

Nitrates in groundwater is a regulatory issue governed by the Irrigated Lands Regulatory Program, which requires all growers in California to prepare a nitrogen management plan each year, starting in 2015. A nitrogen management plan takes into consideration the contribution of various sources of nitrogen other than fertilizer: nitrates in irrigation water, nitrogen in cover crops and nitrogen that is contributed by compost.

An updated in-season nutrient budget model, including early-season leaf sampling guidelines, has been developed under the leadership of Patrick Brown, UC Davis Department of Plant Sciences. These guidelines are given in the document “Almond Early-Season Sampling and In-Season Nitrogen Application Maximizes Productivity, Minimizes Loss.” The guidelines include a protocol for early-season tissue sampling and for applying nitrogen during the season based on crop load and fine-tuned by sampling results.

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1Silva, S.S., S. Muhammad, B. Sanden, E. Laca, P. Brown. Almond Early-Season Sampling and In-Season Nitrogen Application Maximizes Productivity, Minimizes Loss Protocol for Early-Season Sampling and In-Season Nitrogen Budgeting.