Using dairy lagoon water to irrigate silage corn is standard practice. Running the thick, nutrient-rich water through subsurface drip systems (SDI) could someday be just that as two California dairy farms, an irrigation company, and an environmental organization are working together to solve the challenges involved in the water thrifty practice.

For several years DeJager Farms near Chowchilla has irrigated its silage corn with a subsurface irrigation system that blends fresh water with lagoon water through an automated system that is yielding good results.

Together with Netafim, the irrigation company whose system delivers the water through drip tape buried 12-14 inches below the surface on 40-inch spacing, DeJager Farms works with Sustainable Conservation, the San Francisco-based environmental organization that works to unite farmers and industry to find workable, economic solutions to tough challenges. In this case, how can dairies maximize their use of dairy lagoon water through proven SDI technology that saves water.

Through a series of separators, screens and filters, DeJager Farms is finding success that can be measured. DeJager Farm Manager Richie Mayo says he saves about a foot of water per acre per year with SDI in his corn silage while eliminating his need to purchase fertilizer for the crop through the inclusion of the nitrogen-rich lagoon water. Yields in the corn silage remain about 32 tons per acre.

The recycled dairy water is tested biweekly for nutrient levels. Nate Ray, general manager at DeJager Farms says these test results, which look at the amount of total dissolved salts in the water by measuring electrical conductivity (EC), can vary due to rain and ration changes they may make with the milk herd. Those test results will then determine how much lagoon water is mixed with fresh water sources. Even fresh water sources can vary, depending on whether it is pumped from underground or taken by canal delivery from surface water sources.

The purpose of this testing is to ensure the correct amount of nitrogen from the lagoon water is added to the crop without allowing nitrogen to move past the root zone. DeJager Farms sustains its forage needs for 25,000 cows across several dairies by farming the alfalfa, silage and other forages it requires.

The largest change in DeJager’s system since installation is the move to automation. Prior to that water mixing was done manually by opening and closing valves on a trial-and-error basis, Ray says. Now that automation allows DeJager Farms to control irrigation timing and system back flushes by computer. Energy efficiency is gained using variable speed drives.

The program has been a learning process for the irrigation company, according to Domonic Rossini of Netafim. For instance, prevailing winds at the dairies meant placing screens and filter stations necessary to filter the lagoon water on the up-wind side of lagoons. Gauges monitor water flow in separate enclosed systems that deliver fresh water and lagoon water that is later blended.

Blending that water proved a challenge too as the chemical compounds in the lagoon water was destructive to valves.

Later this fall Ray says he will convert some of his corn fields to alfalfa, leaving in the SDI in the lagoon and fresh water system at its current depth and spacing. Ray uses SDI elsewhere on the farm, solely with fresh water, to irrigate other alfalfa fields.

Sustainable Conservation

The Bay Area-based non-profit helps farmers throughout California address environmental challenges affecting the region’s land, air and water.

The DeJager Farms project, and one at the nearby McRee Dairy, are part of Sustainable Conservation’s plan to field-test new technologies that transform the polluting effects of dairy manure into useful projects. Through this, Sustainable Conservation hopes to educate lawmakers and policy makers about the positive potential of manure composting and its effective use on crops.

Through its work so far with the two central California dairies Sustainable Conservation is showing a 15 percent increase in crop yield with 50 percent less water used and a 95 percent increase in nitrogen-use efficiency.

The organization also has projects in California that include groundwater recharge in wine grapes.