Back in the ’60s and ’70s, it was normal to see almond orchards planted on 26-foot spacings with wide openings between the trees and lots of sunlight hitting the orchard floor. These trees were pruned annually to encourage new growth and to remove dead wood.
Moderate rates of nitrogen were applied — some of it inefficiently — and few foliar nutrients and soil-applied nutritional amendments were utilized. Irrigation technology was much more primitive and grower-based soil monitoring and climate measuring devices were essentially non-existent. Pest phenology models and management tools were not well understood and pheromone traps or mating disruption devices were not yet invented.
Yield goals of 2,000 pounds of meats per acre were considered highly successful.
Fast forward to today. Row spacings are now typically 21 to 22 feet wide with trees spaced within the rows at 15 to 16 feet. Tree counts went from 67 trees per acre to the current 124 to 132. Trees are pruned/trained in the first two growing seasons and little-to-no annual pruning is done after that.
Higher rates of nitrogen are more efficiently applied in multiple smaller pulses throughout the growing season during peak demand periods. A series of foliar nutrients are applied during the spring, summer, and postharvest periods. Soil amendments, modifiers, composts, tea solutions, and microbial enhancements are being utilized. Most growers have some type of soil moisture measuring systems or employ monitoring services, and irrigation is based on real-time evapotranspiration (ET).
Environmentally friendly insect growth regulators, pheromone monitoring traps, and mating disruption systems are becoming standard practices. Yield goals of 3,000 to 4,000 pounds of meats per acre are achievable.
New Mentality Needed
So, what is the point of all this information? Currently, there is a different philosophy of what constitutes a “normal” orchard. In the past, a normal orchard had moderate vigor, was pruned to open the canopy to allow sunlight penetration, and had healthy fruiting branches up and down the entire bearing canopy.
With the “new normal” has come a different mentality regarding the orchard canopy. Dense branching with little sunlight penetration to the orchard floor is common. Humidity within the orchard is high, even when it is not being irrigated. Trees are pushed hard for early production, growth is much more rank, and heavy bearing weeping “hangers” fill the drive rows with many broken limbs during heavy crop years. Hullrot is much more prominent and though diseases such as blossom brown rot and shothole are still concerns, and scab, rust, and Alternaria have taken center stage.
With all of this, the presence of lower limb dieback caused by many factors known and unknown is becoming much more common. Ironically, this is not necessarily an indication of improper management. Many of the California’s most highly productive orchards have extensive lower limb dieback and large amounts of limb losses to hullrot (Rhizopus and Monilinia). Some have even referred to these disorders as the “gout” of the almond industry (i.e. high inputs = high yields = high crop protection budget).
I used to think if an orchard had large amounts of lower limb die-back or hullrot that the trees were being over-irrigated, over-fertilized, or being pushed too hard to produce. While this may be partially true, some of the most productive orchards in some of the most fertile growing regions like Firebaugh in West Fresno County have orchards where it is virtually impossible to take a leaf sample due to no live limbs within ground’s reach. Many of these orchards have total death of all lower limbs due to hullrot, lower limb dieback or shading out, yet consistently average 3,000 to 3,500 pounds per acre and occasionally exceed 4,000 pounds per acre.
The key to this philosophy is maintaining a healthy canopy by properly managing irrigation, nutrition, and pests. It does not matter where that canopy is. In the case of areas such as Firebaugh, the entire bearing canopy may be on the tops of the trees. If this canopy is healthy and has 70% to 80% light interception, there is no reason that it cannot achieve maximum yields. As the saying goes, “You cannot judge a book by its cover.” Well, you cannot negatively judge an almond orchard just because it has no live lower limbs.