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Grower trial: Super high density almond planting on dwarf rootstock holds promise

The Lyons family has embarked on an experimental plot of super high density (SHD) almonds using dwarf rootstock.

Thinking small can work just fine.

Such is the case at the Mapes Ranch located west of Modesto where the Lyons family has embarked on an experimental plot of super high density (SHD) almonds using dwarf rootstock.

The trees are self-pollinating.

While there are other trials in California, some bigger than this nine-acre planting, Billy Lyons, the ranch’s manager, is perhaps the most willing of California growers experimenting with high density to talk about it.

While he emphasizes his planting is still in the pilot stage and he’s taking it year to year, he is pleased with how things are progressing in its third year.

In the second year, the yield was 500 pounds per acre. Lyons says most growers do not harvest almonds in second leaf.

He declined to disclose what his 2016 yield was but says it was enough to keep the trees in the ground. Lyons will say yield exceeded normal expectations in the third year of a conventional planting, 1,000 to 1,400 pounds depending on the variety.

Lyons’ harvest on the plot involves a single pass through the field. This is likely to please the Almond Board of California which supports keeping dust down at harvest.

A conventional harvest involves three passes – one with a shaker which drops nuts to the orchard floor, another with a sweeper that puts them in windrows, and a third that picks up the nuts.

In the Mapes plot, a modified olive harvester drives along one side of a tree row, dropping almonds into a gondola pulled along the other side of the row. The nuts do not reach the orchard floor.

Lyons, son of former California food and agriculture secretary Bill Lyons Jr., became enamored with the idea of trying out SHD after traveling to Spain where he saw SHD plantings.

Travelling with him was Cliff Little, a friend of Lyons and the chief executive officer of Agromillora, a nursery in Gridley, Calif. which produces high-density olives worldwide and is producing hybrid rootstock for other species including peaches, nectarines, and plums.

Agromillora is headquartered in Barcelona, Spain.

Upon seeing the Spanish plantings, Lyons said, “This could work.”

It turns out the developer of the non-pollinated cultivar, Zaiger Genetics, is practically a neighbor of Lyons. Zaiger Family Genetics created the self-fertile variety Independence. It was grown for the test plot by Dave Wilson Nursery of Hickman using Rootpac 20 rootstock.

The rootstock reduced the tree’s size and added to the benefits of high density.

Lyons was unable to plant conventional trees on the plot since it has a higher water table. He believes the dwarfing rootstock with a smaller root zone will work. He also thinks there could be less water usage and better efficiency with nutrients and fertilizers due to a smaller root zone.

The trees are topped and hedged mechanically.

For Lyons, it’s not purely a matter of yield size. He believes he must take margins into account as well, seeking to keep his inputs low so he profits even if yields fall. He’s achieving this by cutting passes across the plot, mechanizing operations, using fewer bees for pollination, and putting in place other efficiencies tied to tree dwarfing.

He’s using just one variety to reduce the need for multiple harvests.

SHD has several potential benefits and drawbacks. The potential advantages include:

  • Mechanized pruning;
  • Increased airflow; and
  • Reduced dust during harvest

The option of harvesting without soil contact reduces the risk of contamination by soil-bound pathogens.

Possible disadvantages include harvester damage to the trees, but Lyons says the tree trunk is not shaken as is customary with a conventional harvest.

Lyons said, “The trunk is the life source of the tree and we’re not touching it.”

Lyons says the harvester requires further modification. Robert Liptrap, research and development manager for Agromillora, said modifying mechanical harvesters is a key issue.

Both face a Catch 22 since it’s difficult to get an equipment manufacturer to make machines until there is acreage in the ground. But growers are reluctant to plant acreage unless they have needed harvesting equipment.

Steve Huffman, sales representative with Agromillora, says there are five trials in California which were harvested this year.

“We have an 80-acre trial that was planted this past winter and a 155-acre trial that will be planted next month,” Huffman said. “We have about a dozen trials in all up and down the state.”

In Europe, more than 5,000 acres of high density almonds have been planted. Little said this number is expected to double over the next few years.

Little cautions that growers who are weighing whether to plant SHD trials need to be aware “we don’t have 15 years of data here in California. We simply don’t have long-term data on the rootstock-variety complement.”

Lyons adds, “This may work for some people, but not for everybody.”

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