Confusion continues to cloud how growers can best do their part to cut down on underground water contamination in the most productive area of California’s Central Valley.

But regulators appear to have backed off some requirements that could have greatly boosted the cost to farmers, said David Orth, general manager of the Kings River Conservation District and coordinator of a coalition representing farmers in the four county areas of Fresno, Tulare, Kings and Kern.

Orth was among speakers at a Fall Citrus Meeting in Tulare County and spoke on the Irrigated Lands Regulatory Program. Other speakers addressed irrigation and nutrient management to prevent leaching of contaminants into groundwater, alternate bearing in citrus and frost protection.

Orth said the Southern San Joaquin Valley Water Quality Coalition represents farmers tilling 1 million acres, but farmers on more than another million acres in the four counties have not joined the group.

One reason, he said, is that regulators have not made it clear to them what their alternatives are. An argument for joining the coalition has been that individuals outside the coalition would have to face individual regulation.

“They may think that they can attempt to prove there is not a discharge from their land,” Orth said. “That has been easier to prove when it involves surface water, but tougher with ground water.”

He cautioned growers not to ignore calls for sediment and erosion control plans, saying there is a “civil liability” in that. Orth said the regional water board staff has assessed significant fines that range into “five and six figures.”

Orth said the board has moved to nitrogen management plans for growers that would rely on ratios rather than going into individual “proposed and final accounting” budgets.

Orth said the engagement of commodity groups on the issue of keeping nitrates out of drinking water has helped coalitions, most notably at a meeting that drew some 400 people to a meeting of the Central Valley Regional Water Quality Control Board in Tulare in August. He would like to see more “field trials with commodity groups” on nitrogen use.

Orth said regulators appear to have backed away from requirements that would have directed that nutrient management plans must be prepared by a specialist certified to do that. He said they also appear ready to drop a requirement that a licensed civil engineer would have to be hired for newly constructed or modified ponds, basins or tail water recovery systems.

He said any future costs will be “heavily dependent upon the level of monitoring” that growers would have to pay for. He called monitoring “the single most expensive thing” for the coalition. Orth said there remains much uncertainty about how the monitoring will be done and how its results will be used.

“The uncertainty about this is what a lot of us are concerned about,” he said.

Orth pointed out a Central Valley Water Board meeting will be held Nov. 30 in the Bakersfield area. It will include a discussion of the Eastern San Joaquin River watershed and Tulare Lake Basin waste discharge requirements. The meeting, location, starting time and agenda will be posted on the board’s web site, http://www.waterboards.ca.gov/centralvalley/ at least 10 days before Nov. 30.

Leaching problems

One way to keep nitrates out of the groundwater is to avoid leaching, said Larry Schwankl, irrigation management specialist with the University of California Kearney Research and Extension Center.

“Nitrates won’t be leached if there is not water to move them,” he said.

The water to move any contaminants downward comes from rainfall or irrigation. Schwankl said applying nitrogen at the correct time and in the correct amounts is key.

“You don’t want excess nitrate in the soil going into the winter rains since it could be leached by rainfall,” he said.

Schwankl pointed out that some compounds of nitrogen other than nitrates — notably ammonium or organic forms — do not readily leach.

“From a production issue and from a pollution issue, it is important not to have leaching,” he said, pointing out that it’s most productive to have nutrients remain in the root zone.

Determining water needs and application rates is important to avoid the over-watering that leads to leaching, Schwankl said. Clogging of lines and variability in applying irrigation water can lead to over-watering as a grower seeks to assure that under-watered areas get enough moisture.

Richard Snyder, a biometeorology specialist with UC Davis, talked of how water and wind machines can be used on citrus to prevent cold weather damage. He referred participants in the meeting to the website http://biomet.ucdavis.edu/ that offers a wealth of information on frost protection, including videos in Spanish and English.

He explained damage caused to the fruit by formation of ice outside cells that draws water out, resulting in dehydration.

One of the best ways to protect against frost is site selection, Snyder said. Avoiding low spots where cold air will collect is critical for citrus and for vineyards, he said, recalling how winemaker Joseph Gallo sought advice on where to plant grapes.

Snyder said it can be helpful to remove “cold air dams” that keep the air from drifting out of an area. Likewise, he said, it may help to add hay bales, plastic fences or other impediments to divert cold air away from a grove.

Ground cover in citrus is not helpful when it comes to keeping the floor of the grove warm, Snyder said. It reflects sunlight and results in some energy loss. “It doesn’t store as much heat,” he said.

Water from sprinklers under trees is most effective when it is allowed to freeze, Snyder said. The water should not be sprayed into trees. But for furrow irrigation, he said, the water should not be allowed to freeze, and furrows should be on the edge of trees, not directly below them.

Covers and wraps can help for younger citrus, but they should be waterproof, Snyder said.

“The enemy is evaporation,” Snyder said, pointing out that it is necessary to cool and freeze six times as much water as is lost to evaporation, and evaporation depends on the dew point and wind speed.

Carol Lovatt, professor of botany and plant sciences, at UC Riverside, is studying alternate bearing in citrus. She said that holding an “on” crop on the tree for harvest exacerbates the problem of alternate bearing.

Early harvest of the on crop in November or December will increase spring bud break and yield the next year, Lovatt said. She adds that fruit thinning in early July of an on crop will increase the number of shoots without fruit and thus increase vegetative shoot growth and return bloom and should mean a higher yield and increased fruit size.

To limit the number of fruit without thinning, Lovatt is exploring the use of plant growth regulators.

She said it is important to fertilize for the current crop load, not to replace what the previous crop used.