To take and utilize an early season leaf sample for estimating of seasonal nitrogen needs, follow the UC Early Season Protocol (UC ESP) for leaf sampling (details below). So far, this program has only been tested on Nonpareil, but it should work well for other varieties. (Dr. Brown’s lab is working up the details for a Monterey variety sampling protocol. For now, here’s how to take leaf samples using the new UC protocol worked up for Nonpareil:
- Sample leaves approximately 43 days (plus or minus 6 days) after full bloom. It is very important to hit this range of sampling dates, as leaf nutrient levels change with age and too old or too new leaves in the sample could result in an inaccurate report. If you sample outside the sampling “window”, mark the date on the sample bag. At Nickels this year, Non-pareil full bloom was the last week of February. Call it Feb 26. So we will target early leaf sampling the week of April 8 at Nickels Soil Lab.
- Collect leaves from 18-28 trees per orchard. Target uniform, representative trees from the block to sample. Sample trees must be at least 90 feet apart. From each tree, sample all the leaves of 5–8 non-fruiting, well-exposed spurs. Combine all the leaves in a single sample bag. A minimum of 100 leaves per sample bag is required.
- Send the samples to a reputable lab – check with your PCA and/or ask around for a good, reliable lab if you don’t currently use one — and ask for a FULL NUTRIENT ANALYSIS (N, P, K, B, Ca, Zn, Cu, Fe, Mg, Mn, S) and application of the UCD-ESP program. A good lab should have the results back to you in a week, maybe two.
Review results from UCD-ESP program and your cropload estimates. See step four and the corresponding tables from the article titled “Nitrogen Management in Mature Orchards, Part 2.“Sample leaves again in July to check these new practices. Dr. Brown suggests following the same protocol for sampling leaves in July as in April: 18-28 trees, each tree at least 90’ apart, all the leaves of 5–8 non-fruiting, well-exposed spurs from each tree, all the leaves in a single sample bag and a minimum of 100 leaves per sample bag.
For more information, please see the “Crop Nutrient Status and Demand for Almond” website developed by Patrick Brown, Saiful Muhammad, and Sebastian Saa Silva.