Bob Curtis knows a lot about almonds … and marriage. He’s been involved in both for 22 and 38 years, respectively.

Curtis, the Almond Board of California’s associate director of agricultural affairs, says pivotal decisions to design and develop a new almond orchard mirror the choices which lead to a long-term, successful marriage.

“The decisions almond growers make early to plant a new orchard is similar to picking the right person to marry,” Curtis says. “The decisions for both form a foundation on what you will live with for the next 20-25 years.”

Curtis shared this accurate comparison as he moderated the “Designing and Developing a New Almond Orchard” workshop at the 2012 Almond Industry Conference held in Sacramento, Calif. in December.

The conference was attended by 2,400-plus California almond growers, hullers, marketers, and other industry enthusiasts.

California growers produce 99 percent of the U.S. commercial almond crop. The economic value of California almonds is about $3.8 billion annually (2011 figure), according to the California Department of Food and Agriculture.

Three University of California specialists laid out a roadmap on how to best design and develop new orchards - new ground for almonds plantings or replanting older orchards.

Roger Duncan, UC Cooperative Extension (UCCE) farm advisor in Stanislaus County, says many decisions are made before ever turning the soil.

“The design of a new orchard should emphasize efforts to boost the capture of light which in turn increases yield potential,” Duncan said. “About 80 percent of the light in an orchard must be captured to produce a 4,000-pound-per-acre crop.”

Duncan cited research findings by UC’s Bruce Lampinen; every 1 percent increase in light interception equals about 50 additional pounds of yield potential per acre.

Today, the average California almond orchards capture 50 percent to 60 percent of the light.

“The keys to maximum light interception include the integration of appropriate rootstock, planting density-tree arrangement, and minimal pruning,” Duncan said.

Yield is just one factor to consider when selecting a good rootstock. Other factors include saline levels in irrigation water, soil fungi, nematodes, water saturation, and the pH level.

Duncan says select a rootstock which handles local soil situations the best.

“The best offense is a good defense. Think of the rootstock as your protection against premature orchard decline.”

The Nemaguard peach rootstock is the “workhorse” in San Joaquin Valley almond production. Duncan says the rootstock’s key advantages include “immunity” to the root knot nematode, good vigor, and “decent” anchorage. Its best fit is in sandy loam and loam soils.

Disadvantages include susceptibility to the ring and root lesion nematodes, bacterial canker, phytophthora root rot, oak root fungus, crown gall, and salt injury.

No rootstock is perfect, Duncan says; each has its pros and cons.

In an alkaline soil-high saline water situation, Duncan suggests a peach-almond hybrid rootstock. Hybrids provide high vigor, plus better pH and salt tolerance than peach rootstock, along with good anchorage.

In a replant situation, the farm advisor says a peach-almond hybrid can outperform Nemaguard if planting back into a previous Nemaguard orchard, as long as ring nematodes are not present. Hansen and other peach-almond hybrids are very susceptible to ring nematode and bacterial canker.

If ring nematode and bacterial canker exist in sandy soils, Duncan suggests the Viking and Lovell rootstocks.

Mariana 26-24 is the standard rootstock for poorly-drained soils and a preferred answer in areas with oak root fungus. The Krymsk 86 type from Russia is gaining popularity in the Sacramento Valley for the rootstock’s good anchorage performance, especially given the area’s high winds. Krymsk 86 appears to have tolerance against Phytophthora root rot as Marianna plum.

Duncan will continue to study the new Empyrean 1 rootstock which is highly vigorous and offers root knot nematode resistance.

Selecting almond varieties depends on many factors. Yield and nut price (gross income) are important, but so are the bloom overlap with the main variety, the harvest date, insect and disease pressure, kernel quality, farm size, personal preference, and how much risk a grower is willing to accept.

Before making a decision on variety, Duncan says ask two key questions to a respected handler-seller: first, ask which varieties will likely sell well in five years out; and second, which almond varieties should receive the best prices if an almond oversupply occurs.

Other key issues in new orchard plantings include tree spacing and pruning. Duncan has conducted tree planting density trials with 10’-by-22’, 14’-by-22’, 18’-by-22’, and 22’-by-22’ spacings.

The findings — closer-planted trees resulted in significantly smaller trees. High-density planting resulted in higher yields for low and moderately vigorous trees, but little yield differences in highly-vigorous trees including Nonpareil on Hansen rootstock.

Closer-spaced trees have less scaffold breakage. Smaller trees are easier to shake which reduces tree shaker injury and mummies (blanks). If a smaller tree dies, the yield loss is less versus a larger tree.

Many good reasons exist to prune new orchards. Duncan says pruning does not increase yield.

David Doll, UCCE Merced County farm advisor, shifted the conversation to site evaluation, fumigation, and planting. He said one of the best decisions a grower can ever make is to ask a farm advisor for guidance before field work begins.

“Learn from the old orchard,” Doll said. “Closely examine the ground before you start or your decisions will come back to haunt you.”

Doll says to view online aerial field images from Google Earth and the Natural Resources Conservation Service. Then overlay the maps to determine field weaknesses and the causes. It may also help to map the electrical conductivity of the soil.

Some field weak spots can be solved through irrigation, planting density, and pre-plant amendments.

A smart move to determine what’s under the ground (good and bad) is to dig six or seven backhoe pits across a field. Examine the soil layers, peruse previously unseen problems, and take soil samples at several depths.

How to physically remove an old orchard also deserves close scrutiny. Common options include grinding the trees and hauling the chips away. The “stack and burn” method is less common in many areas due to air quality restrictions.

A method in the experimental stage uses a 40-ton rototiller called the “Iron Wolf” to grind, shred, and incorporate trees back into the soil. This method has been shown to increase soil organic matter.

Doll says carefully evaluate each option’s advantages and disadvantages.

Soil fumigation can be a smart financial decision during orchard development. A fumigated tree usually has improved feeder root development which increases water and nutrient uptake. This can result in larger trees, earlier harvests, and higher yields. Depending on the replant issues present, fumigation can occur as a broadcast or rowstrip application 24 inches deep.

When to fumigate and not fumigate is a common question. In virgin ground with no nematodes, Doll said save the money, and then chuckled, “Go out and buy a new tractor.” There is no reason to fumigate.

In ground without an orchard history but with nematodes, use a broadcast or rowstrip application of Telone II, depending on detected populations.

In a field with an orchard history without nematodes, a row strip of chloropicrin can provide good tree results. In an orchard history with nematodes, apply either Telone II as a broadcast or a Telone II-C35 fumigant combination as a rowstrip. 

Doll conducted fumigation trials from 2006-2010 where he compared the impact of fumigation on almond yield and net return. Fumigation, where applied, generated more nuts and about $3,500 to $3,800 more income per acre.

Another question often is whether to plant orchards on the flat or on a berm. Soil texture can impact which method is best. In sandy loam and finer soils, an eight-inch-high, five-foot-wide berm usually works well.

On conclusion, Doll said, “An ounce of prevention is worth a pound of cure. Take the time to develop the orchard properly.”

A third perspective on orchard development was discussed by Kent Shackel, UC plant scientist, also known as Dr. H₂O. Shackel said almond trees are very drought resistant yet are also very responsive to water inputs.

Similar to humans, almond trees need some water to survive, but almond leaves need a constant supply of water to be productive.

“The use of water management tools and paying close attention to irrigation management in young orchards will set the stage for maximum yields later on,” Shackel said.

Valuable California water data for almond growers is available online at http://www.cimis.water.ca.gov/ and http://www.wateright.org/.

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