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Maximizing wine grape water use

Remnants of dryland almonds and prune production are interspersed with the oaks that dot the hills around Paso Robles, Calif.

For 82-year-old Jim Lockshaw, they are reminders of his early days of farming 30 years ago when he left the Los Angeles area for a more peaceful life in San Luis Obispo County, Calif. The 80 acres he bought included four acres of dryland Zinfandel grapes and the rest was made up of almonds. He made wine from the Zinfandel grapes and later established Twin Hills Winery.

It was the seventh winery established in the Paso Robles area. Today there are more than 200 in California’s newest premium wine grape growing area. He sold the winery 15 years ago, and bought more land, where he is growing grapes with his son Curtis. Curtis, who moved to the area 11 years ago, farms 40 acres of Zinfandel, Cabernet and Syrah. Their vineyard is called Oak Flat Vineyard.

Lockshaw has witnessed the modern day wine grape transformation that first began east of town three decades ago where there is an underground aquifer feeding large vineyard blocks. West of town where Lockshaw and his son Curtis farm, water has always been scarce, and the vineyards are much smaller because of the limited water supply.

There remain many dryland vineyards nearby, but drip irrigation has made this Western area explode into a premium wine grape growing locale.

However, even with drip the water supply is tenuous. Curtis begins the season pumping from about 100 feet to feed his vines the necessary 8 gallons per week from May through October to produce 3 tons per acre. By October, he may be pumping from 200 feet or more. Hopefully, it will recharge over the winter, but the last three years of drought in California have taken their toll on the water supplies from wells.

Curtis and his father have been able to manage with their limited supply. Others are not so fortunate. One winery the Lockshaws sell grapes to also farms 80 acres and the owner is forced to truck in water to produce a crop.

Drip irrigation is by far the most efficient way to get water to the vines and has been a key reason for the Paso Robles wine grape explosion. However, the elder Lockshaw has long thought there must be a better way.

“Unfortunately, even with conventional drip much of the water evaporates or is blown away and fertilizers that do not percolate into the subsoil support unwanted weed growth and can run off,” he said.

Lockshaw is experimenting with changing the way to drip irrigate with a half-acre of newly planted Grenache wine grapes irrigated with a system that delivers water beneath the soil directly to the plant roots.

“So far it seems to work well,” he says.

The vines in Lockshaw’s young experimental vineyard used only 3 gallons per week per vine this last year, compared to the 8 gallons for Curtis’ conventional drip irrigated vineyard.

“The vines are still young, and we need to see how this will work a few years out. However, I am encouraged,” said the elder Lockshaw.

The irrigation system starts with augering a hole 12 inches in diameter and 36 inches deep for each vine. A grape stake is positioned into the hole with a half-inch PVC pipe taped to the stake. The PVC pipe is inserted 24 inches into the ground next to the vine and extends 12 inches above ground. The hole is filled half full with pea gravel and the remainder of the hole is filled with soil. “We added a growth pellet to each hole when we planted,” he noted.

The half-inch PVC pipe is capped initially when the dripper hose is inserted directly to the plant grow tube, and the tubing is then connected to an emitter tapped into the main line suspended from the grape stake.

“When the new plant shows enough vigor, we punch a hole through the half-inch cap and transfer the dripper hose into the top of the pipe. This deep watering forces the root system away from the surface,” he said. “The first crop was excellent quality and used less than half the water we normally would with surface drip irrigation,” he said.

With no water on the surface of the vine rows, there were no weeds during the season. Winter rains generate weeds, however, and those are cleaned out.

With drip irrigation, you have to make sure each dripper is functioning properly. “It has been quite simple to pull the dripper hose out of the PVC cap to check that the drippers are functioning,” he said.

“We plan on adding nutrients through the drip system as needed. Because the nutrients are not supporting surface weeds it should require proportionally less,” he said.

The pea gravel is the key to the underground water system. It allows the water to be dispersed into the root zone of the vine.

Lockshaw also used the Grenache vineyard to experiment with a trellising system. The vine rows are only 6 feet wide with 4 feet between vines compared to the family’s commercial vineyard which is planted 10-by-8 feet. There is only one wire in the experimental vineyard to support the cordon positioned atop each large, round grapestake. The cordon is 5 feet high compared to the 3 to 4 feet for Curtis Lockshaw’s VSP trellised vineyard.

“The cordon is probably about 6 inches too high. The tall cordon is to allow pruners and pickers to work without bending over. The idea is to put the work area about shoulder high,” he said.

“Paso Robles has proven to be a great area for growing premium wine grapes with irrigation. But we need water ... Dad’s idea is to do more with less water,” said Curtis.

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TAGS: Grapes
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