Source: Sustainable Conservation

By Cecilia Parsons on behalf of Sustainable Conservation

As the California drought continues, higher yields per acre, coupled with the critical need to use water more efficiently, are making silage and alfalfa growers take another look at both subsurface and ground level drip irrigation solutions for their crops.

“Yields and water use efficiency are driving demand for this technology,” Todd Rinkenberger, Regional Manager for NetafimUSA confirmed. NetafimUSA  is a producter of drip irrigation solutions with local offices and a manufacturing plant in Fresno, Calif., where they manufacture a comprehensive line of drip/micro irrigation products. Rinkenberger observes that as the drought continues, his company is seeing dramatic changes in the use of drip irrigation solutions for orchards and row crops in the Central Valley.

Alfalfa growers tend to use the more permanent subsurface systems while corn silage growers have a need for flexibility with both surface and subsurface delivery.

Subsurface drip is the application of water below the soil surface through emitters with discharge rates in generally the same range as surface drip. Drip lines with a lifetime of 6-12 years are buried 8-18 inches below the surface on 30-80 inch centers between lateral drip lines depending on soil type. Surface drip tape has the same setup only the tape is on the surface and used only once.

A pressurized system, as well as filtering and filter maintenance system, are necessary for drip irrigation with all crops. Water treatment capability and fertilizer injection are also required.

De Jager Farms Inc., a custom farming company that manages 17,000 acres of dairy forage and alfalfa production in Chowchilla, Calif., is an early adopter of subsurface drip in corn silage. Nate Ray, one of the farm managers at De Jager farms, has been actively involved in converting fields from flood to drip irrigation.

“We decided to go that route three years ago as the water shortage began,” said Ray. “The potential for water savings with subsurface drip prompted us to look for an alternative to flood.”

Ray said the first field was chosen because of its lower water holding capacity. He also believed subsurface drip had the potential for better field uniformity and irrigation efficiency. He is also pleased with the yields from his first silage field. Compared to adjacent fields under flood, the 180 acres of corn silage yielded three tons plus per acre, using an acre foot less water.

With flood, corn silage takes 40 inches depending on soil type. Ray said they applied just under 30 inches.

Switch to Strip-Till

The transition to buried drip however requires a significant change in approach to tillage practices. In order to utilize subsurface drip lines for row crops, tillage can now only occur between rows. Tilling the entire field will destroy buried drip tape, so a transition to strip-till, a form of conservation tillage, becomes necessary. 

Strip-till involves disturbing only a narrow strip of land where the crop is planted using precision guidance while leaving the rest of the field intact. The buried drip system therefore fits well with De Jager Farms because they already had years of success with the strip-till system, Ray said.

The initial subsurface drip field had been in a strip-till corn and no-till winter forage rotation. Ray said they did a flood pre-irrigation, planted, then shanked in the drip lines eight inches below the surface. They did not want to go deeper with the drip, he said because lighter soils make it more difficult to push water out.

Combining this technology with conservation tillage delivers additional water saving benefits. The soil’s capacity to hold water improves as organic matter builds. As a result, the soil also has a high nutrient holding capacity. Ray finds that he is also able to more precisely control nutrient application through the drip irrigation system, a key challenge that many dairy farmers experience with flood irrigation systems.

However, existing drip irrigation systems cannot handle liquid manure, and Ray has had to purchase additional synthetic fertilizers in spite of having plenty of manure, the normal source of nutrients on dairies. Seeing this challenge as an opportunity, De Jager Farms has partnered with Sustainable Conservation and NetafimUSA to test technology that allows liquid manure to be applied through drip systems.

Field selection for subsurface drip is an important consideration Ray said. High gopher populations in fields can affect the integrity of a subsurface system and lead to higher labor costs for eradicating the pests. Ray said he anticipates installing more subsurface systems in alfalfa and working more silage acres into the rotation.

Weathering Drought

Two Merced-area growers report successful prior years with surface drip systems in their corn silage crops. Both Kurt New and Matt Strickland are now in their second year of planting corn silage and using surface drip to irrigate. New, who manages crops for TeVelde Farms said he furrow pre–irrigates then installs the drip tape.

New said water conservation is the motivation, keeping fields in production with less water. In his case, subsurface drip does not work because of the high traffic with silage choppers. Their farming operation also employs conventional tillage methods, thought they don’t have experience with strip-till. Strickland also said he went with the surface drip system due to a lack of a GPS system in the tractors he rents.

In the last three years, Rinkenberger said, the number of alfalfa acres irrigated with subsurface drip irrigation as increased statewide. Netafim and University of California Cooperative Extension alfalfa specialist Dan Putnam pegged the growth to 4% of the total alfalfa acres in the state. Rinkenberger said the highest rates are in the Valley areas from Woodland to Bakersfield. Drip adopters in silage are fewer, but the growth there is centered in the higher dairy production areas of Merced, Stanislaus, Tulare, and Kings counties.

The USDA’s Natural Resources Conservation Service has cost share funding for growers who adopt conservation tillage practices. The Environmental Quality Incentives Program (EQIP) pays about $18 per acre for growers who enter into a contract for implementing no-till or strip-till on their fields. Similar cost share funding also exists for drip irrigation projects.

About Sustainable Conservation

Sustainable Conservation is a conservation organization with an office in the Central Valley working to promote low intensity tillage and irrigation efficiency practices that have both an economic and environmental benefit. Ladi Asgill, Sr. Project Manager, indicates that as more farmers consider integrating drip irrigation with strip-till, there are many experienced farmers in the Valley willing to share their experiences with others. Asgill is excited about the business benefits but encourages farmers considering switching to drip irrigation to think not just about water savings, but also about the impact it could have on their overall nutrient management plan, particularly as it relates to manure application.