Avocado is probably the best crop choice for going organic, because of the good biological control found in most of the groves and the low fertilizer demand. With the leaf mulch and shading, there is much less of a weed problem, and the natural mulch can be a significant source of nutrients for the trees. Organic yardwaste mulches are also used to great effect in Southern California, suppressing weeds, aiding in erosion control, reducing evaporative loss, and aiding in root rot control. Municipal mulches are often delivered very cheaply (the cost is in the spreading), but it is also not uncommon to see a crop of pine, eucalyptus, palm or tomatoes to show up not longer after a mulch has been spread. It is usually fairly easy to remove these when they are young, and then the woody mulch will continue to further suppress weeds. Mulches can also cool an orchard, raising frost hazard, be a fire fuel, and keep soils too wet in high rainfall years. They should not be allowed to accumulate around the tree trunk.
Mulches can also be a significant source of plant nutrients. Organic growers of other crops typically use a combination of foliar sprays (Garrett Juice Plus, THRIVE, BioWash), compost, and cover crops. The nature of the avocado leaf does not lend itself to foliar uptake, so any materials need to be applied by hand or fertigated.
Weeds are commonly cited as the main problem for organic farmers. This is true in young avocado orchards, but with the thick leaf layer in mature orchards, this is much less of a problem. Canopies should be kept low to the ground, especially on slopes to make sure wind does not blow the mulch away. Most growers use mowing or weed whips as the primary control for weeds. Growers also use mulches and cover crops as part of their control method.
Source: California Avocado Society 2008 Yearbook 91:35-43