The 2012 ASHS Annual Conference

Calculating the appropriate rate of fertilizer to apply is a complex process that involves interpretation of leaf and soil analyses, and a range of orchard and site condition factors.  A online computer program was developed so avocado growers can calculate their own fertilizer recommendations (nutrient, application time, and rate) based on tree phenology, a grower-supplied estimate of crop load, and an estimate of vegetative growth. Computer-based fertilizer recommendations have been successfully adopted by growers for crops such as almond and pistachio and will assist California’s 6,000 avocado growers match fertilizer applications with tree nutrient demands.  In a typical well-managed avocado orchard with reasonably fertile soil, nitrogen, potassium, and zinc are likely to be the only nutrients that need to be applied regularly.  Thus, fertilization recommendations are provided for these nutrients. Input for our avocado nutrient fertilization model includes: crop load, canopy size, leaf nitrogen, potassium, zinc, soil texture, and irrigation rate.  Avocado trees are unique because the fruits can remain on the tree for 15 to 18 months after full bloom (two growing seasons).  The tree must support the growing fruitlets and the maturing fruit from the previous growing season.  Moreover, both developing and maturing fruit are strong sink for nutrients.  Recent modifications to the avocado nutrient fertilization model included developing fruitlets and maturing fruit in the avocado nutrient model. The model is currently being field tested.