- Author: Gary S. Bender
I just raked up all the leaves under the avocado and it looks so nice. PUT THEM RIGHT BACK. The avocado is shallow-rooted and really depends on the natural leaf mulch to protect its roots. In fact the roots will actually colonize the rotted leaves as if it were soil. This mulch is also a first line of defense against root rot. The decomposing leaves create a hostile environment to the microorganism that causes the disease. The mulch also helps to reduce evaporative loss of water and therefore reduces water needs. Avocado growers will actually spread mulch in cases where trees are too young to produce adequate leaf drop for mulch or in windy areas where mulch has blown away. The key to remember is that the mulch should be kept at least six inches away from the trunk to avoid collar rot which can be causes by keeping a moist mulch against the trunk.
- Author: Gary Bender
Farmers in our county who are using high-priced water are really thinking about “niches” in the market. They
simply must get the best prices they can if they are going to stay in business.
So, what are these “niches”? One niche is simply converting to an organic operation. This can usually mean higher prices, but the increase in cultural costs must be carefully considered (spraying glyphosate for weed control is a lot cheaper than hoeing, but glyphosate is not organic!). It can be an early variety that hits the market ahead of other areas (early season, low-chill blueberries), or it can be a crop that is later than other farming districts (Gold Nugget mandarins), or it can be a crop that is desired by a local market (tropical guavas for the Hispanic population).
We might have a niche local market for hops developing right before our eyes. According to Wikepedia, San Diego has 87 craft breweries and brewpubs, with 31 more on the drawing boards. I have heard that our local craft beer makers might like to buy local hops.
But, can they be grown here? Over the last 30 years I have tried to steer growers away from growing crops that have a high chilling requirement. I've talked would-be pistachio and cherry growers from planting because they both have winter chilling requirements in excess of 900-1000 hrs below 45 F. In the case of hops, they have a chilling requirement and we think a long daylight requirement, which they get in the Northern climates. And I've told a lot of people that hops don't do well south of San Francisco (because that's what I read on the internet). But some people planted hops anyway, and guess what! They do grow here!
But they don't always bear fruit (cones). Local growers have told me that ‘Willamette', ‘Centennial' and ‘Northern Brewer' do not produce well. But ‘Cascade' and ‘Nugget' have been producing from young vines at the Star B Ranch in Ramona. And other growers have been able to produce with 'Chinook', ‘Galena', ‘Perle' and ‘Tomahawk'. Now, will they produce the quantities needed to compete in a commercial market, pay the water bills and make a profit? This sounds like a farm advisor trial in the making!
You may wish to read a good article on growing hops that was prepared by Gordon W. Morehead and Paul Vossen with UCCE in Sonoma County http://cesonoma.ucanr.edu/files/27166.pdf.
Growing Hops. Hops are usually started from rhizomes (root cuttings) planted in hills about five feet apart in the early spring. Hops grow quickly as vines on a tall trellis. Most growers erect poles about 16-20' tall, run wires between them and drop stings down about five feet apart for the vines to climb. Three trainings are done every fifteen days to get the vines to grow up the stings properly.
For irrigation a local grower in San Diego has reported to me that (in her second year) she used drip irrigation with a 1 gal/hr dripper/plant for 20 hrs in a set, two sets per week. She fertilized 3 times per season with 1 lb 5-1-1 organic fertilizer and liquid fish emulsion (not sure how much) through the irrigation system. She just completed her second year so I'm not sure what her water and fertilizer requirements will be in the third year when the vines are in full production.
Harvesting is done in August-September by cutting down the vines and either taking them to a machine that separated the cones from the leaves and vines, or by hand. In her case she bought a harvester for $14,000 that “is a necessity if you have a lot of vines”. Depending on the requirement of the buyer, the grower may have to dry the cones and chop them. The grower should work out the marketing requirements well in advance of the harvest.
Are hops going to make it as a new crop in San Diego? We don't know, but stay tuned!
Mature avocados may be a big tree, but they have very shallow roots. The bulk of them are in the top 8 inches of soil. The tree therefore does not have access to a large volume of stored water. As opposed to a deep rooted walnut, they need frequent, small amounts of water. A young tree in the summer might need multiple applications per week, but because the root system is small, each application may only be 5-20 gallons. An older tree with its wider rooting pattern may go a week to a month between irrigations depending on the weather and rainfall. Proper irrigation is the best way to keep the avocado from getting root rot. Both over and under irrigation can induce the conditions for root rot, although over irrigation is more common. And remember, it is not just the amount applied at an irrigation, but the timing that is important, as well. Because you are managing such a shallow root system, just poking your finger into the root system will tell you if there is adequate moisture there before you irrigate again.
The canopy is thinning. The leaves are small and yellow. There is dieback in the canopy, with leafless tips on the branches. You dig around under the canopy in the wetted area of the sprinkler and you can't find roots within 6 inches of the soil surface or if you do find them they are black. There is little mulch under the tree. There are weeds growing under the tree. All these are signs of root rot disease. But it is also a sign of lack of water, because that is what is happening – there are no roots to take up water. And one of the things a gardener will often do, is start watering the diseased tree more, thinking it is lack of water, which if it is diseased only makes the condition worse. Adding more water to a tree that can not easily take it up only creates an asphyxiation that makes matters worse. Irrigation and mulch are the two most important factors for avoiding the disease.
So what do you do if you have disease? There are fungicides that are available from the nursery, but there are a number of things that you can do before applying something like that. First of all get a handle on the irrigation. Make sure you are irrigating to the tree's needs. Check soil moisture before irrigating. Make sure the tree is not getting supplemental water from another area such as a lawn sprinkler. Make sure there is a good thick, woody mulch under the canopy. Adding gypsum (15-20 pounds per tree) evenly spread under the canopy can also help, but reviewing and modifying the irrigation practice is the most important thing that you can do.