Franz Niederholzer0 commentsApril 20, 2013Nutrient

A quick review of UC ESP sampling for accurate almond orchard nitrogen fertilization.

This is the first year that the UC Early Season Protocol (UC ESP) model for predicting July almond leaf nitrogen (N) levels from April leaf samples, has been available for public use.  This model was developed by UC Davis researchers led by Dr. Patrick Brown.  Based on calls to several reputable ag labs and questions from PCAs, there seems to be some uncertainty about availability and use of the new model.  Where is the model?  How does is it used?  Who should use it to develop the July leaf N prediction and what should be done with the results?  Does an analytical lab run it for growers and PCA/CCAs?  If the lab doesn’t do it, should/can the grower or their PCA/CCA to do it, and, if so, where is the model?  This blog post is intended to answer these questions and help interested almond industry members use the UC ESP model.

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Franz Niederholzer0 commentsJuly 18, 2012Nutrient

Summer leaf sampling is serious business

It’s July. Among key orchard activities as harvest approaches, it’s time to sample almond leaves for nutrient analysis. The lab analysis report for a leaf sample serves as part of the “report card” for your fertility program for this growing season for a particular variety in a particular block. A previous post from “The Almond Doctor” covers the practice of summer leaf sampling and shows the University of California critical nutrient levels for almond leaves sampled in July. This post will talk about several additional steps to orchard nutrition assessment in summer and to stress the importance of these practices to the commercial success of an orchard. Take separate leaf samples for each variety in a block. Crop load is the key factor determining mature almond tree nitrogen (N) and potassium (K) use. Different almond varieties in the same block can produce different yields and nutrient demand based on their genetic potential and conditions at bloom. If you don’t already, consider taking leaf samples for nutrient analysis from each variety. Use the lab reports and crop yield reports from each variety in the block from this year as background information when it comes time to apply N and/or K fertilizer for next year. If you applied the same amount of N and K fertilizer this season to all trees in an orchard, yet the Non-pareil yield was off and the Monterey yield was high, can you see that reflected in the leaf analysis reports? Variety specific leaf analysis and cropload data can help you understand how different varieties use expensive nutrients and how you might possibly fine tune your fertilizer delivery to optimize yield without wasting money.  Look up between leaf samples. Adequate tree vigor (growth) is key to good production. Adequate leaf nutrient levels and little to no growth

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David Doll0 commentsMay 19, 2012Nutrient

Estimating Nitrogen Needs = Estimating Your Crop

Research by Dr. Patrick Brown’s group at UC Davis has been reviewing nitrogen use efficiency of almonds. In their studies they have shown that almonds, when properly fertilized (i.e. not over/under-fertilized),  export between 60-65 pounds of N from the orchard for every 1000 kernel pounds harvested. This number includes all green weight removed to achieve the 1000 kernel pound yield – roughly 4000 pounds of hulls, shells, leaves, debris, and kernels. Interestingly enough, they also have found that orchards that are under-fertilized will export less N (65 lbs). Knowing this, is it possible to determine the nitrogen needs of the trees for the season? Simply stated, “Yes,” but only if an accurate estimate of crop can be made. The ability to accurately estimate a crop is gained through experience and the taking of careful notes from the early season to allow comparison with the sheets provided at harvest. Once a crop estimate is determined, the estimated kernel yield/acre can be multiplied by 60 pounds to determine the total amount of N required/acre for that year. Since almond goes through a period of several drops and weather events (i.e. frost, hail, etc), this adjustment can be modified in season to account for the change. Never-the-less, applying only 60 pounds of N for every 1000 kernel pounds will not meet the trees need because the application efficiency of nitrogen is not 100%. Further work within the study demonstrated that almonds are much more efficient than previously thought, with roughly 70-75% of the nitrogen applied through a micro-irrigation system making its way into the tree. Taking this use efficiency into account, we need to multiply the pounds required by crop demand by 1.4, giving a number of 84 pounds of N for every 1000 kernel pounds. So how does all of this relate to nitrogen leaf sampling?

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