Blue Diamond Almond Facts March-April 2021

have 30 days of stored N “on board” to support bloom and early leaf out. Once 70 percent of spur leaf out has occurred, additional N inputs should begin. The exact amount applied with the first N application should be determined by application plan (how many applications will be applied ? ) and annual N budget (see table in this column). Roughly half of the total N demand of the orchard should be meet by the end of April. Small, frequent fertigation events (”shots“) provide the most efficient N application and can be used with leaching fraction calculations to minimize N loss from the root zone. Almond trees can absorb very low levels of nitrogen from the soil solution and so can efficiently access lower concentrations of nitrate delivered in frequent, low N application rates. The following table is presented as an example of the pattern of orchard nitrogen demand (not recommended N fertilizer rate) through the life of a representative orchard, based on 14' x 22' tree spacing, good growing conditions and Nonpareil trees. Almond orchard yield potential varies with location, rootstock, planting density and management. Please use yield data that reflects your actual orchard conditions when looking at this table and developing your own annual nitrogen budget. Data used in this table are taken from Table 2 (pg 8) of the Almond Board of California’s Nitrogen BMPs (see link in this column). Regular irrigation water quality sample analysis should include nitrate. Nitrate-nitrogen (nitrate-N) in the irrigation water is plant available. Every acre-inch of water with 1 ppm nitrate concentration contains 0.05 lb N. Water samples testing at 1 ppm nitrate-N contain 0.2 lb N in an acre-inch. The difference in N content between the two reports with the same numerical value is that nitrate is 23 percent N by weight, while nitrate-N is 100 percent N. Adjust fertilizer rates down, where practical, based on irrigation water nitrate levels. For example, in a mature 50 acre orchard, fertigation to deliver 35 lbs N/acre requires about 500 gallons of UN32 (3.54 lbs N/gal). Orchard nitrogen (N) demand through the life of the orchard based on tree and crop demand (using 14' x 22' spacing; 145 trees/acre) Orchard Age (year) Total Non-yield N demand (leaves + wood) Representative range of good yield for Nonpareil (kernel lbs/acre) Representative crop (hull, shell & kernel) N demand based on kernel lbs/ acre (lbs N/ acre); crop is 6.8% N) Representative total N demand (adding across the shaded columns) lb N/ acre 1 30 0 0 30 (3 oz N/tree) 2 55 0 0 55 (4 oz N/tree) 3 65 750 51 1 1 6 4 55 1 750 1 1 9 1 74 5 45 2750 1 87 232 6 40 2900 1 97 237 7–15 40 2500–31 00 170–21 1 21 0–255 1 6–25 30 1 800–2800 1 22–190 152–220 3 9 M A R C H – A P R I L 2 0 2 1