In addition to being a vegetable farmer, Trevor Hardy is an irrigation expert. During the Mid-Atlantic Fruit and Vegetable Convention, Hardy shared his expertise on how to get water to plants in a timely manner. He said a good irrigation designer partners with the grower to provide a comprehensive irrigation plan for the farm.

Each commonly used irrigation system has benefits and downfalls. “Overhead irrigation is efficient for getting water out, but only 55% of the water is used on the actual crop,” said Hardy. “The rest is wasted.”

In some cases, overhead irrigation is in place for frost protection and can be used on FSMA exempt crops such as sweet corn. “It uses more water and is more expensive to set up,” said Hardy. “It’s more time-consuming and increases disease pressure because it wets the entire plant, the ground and weeds.”

Drip irrigation uses one-third the amount of water because water goes directly to the root zone rather than being wasted through evaporation or runoff.

If the farm includes hills or rolling elevation, system design should be based on the highest point. “This is where the right drip tape will make a big difference,” said Hardy. “Drip tape comes in different spacings and flow rates. Everything has either a Q100 or flow rate that tells how much water it puts out per 100 feet of drip tape.”

He explained the importance of keeping information found on the drip tape roll tag. “Every drip tape has a specific part number,” he said. “Save the drip tape roll tags from the previous year so you always order the right one. If it’s halfway through the season and you have a problem with a product, the first thing the rep will ask is the part number.”

Because water moves differently in different soil types, drip tape should be matched to the soil type. “In clay soils, water pushes out more laterally,” said Hardy. “In sandy soils, water will go straight down because there’s no organic matter to help distribute the water.” With sandy soil, pulse irrigation is necessary throughout the day to make sure water is reaching the root zone.

Hardy recommends monthly removal of end caps and line flushing. This practice will improve the performance and longevity of drip tape as well as show whether pond debris is being caught.

Growers should check regularly for damaged drip tape. Hardy said the biggest issue with drip tape damage is due to the user not checking the plastic and drip tape applicator when laying it in the field.

“The pipe that all the drip tape goes through wears as it sits in the dirt,” he said. “Check that annually at minimum. If you’re laying a lot of plastic, check twice a week. A small, sharp edge will damage drip tape and sometimes cut it or make holes.”

Hardy explained pump options for irrigation systems, including volume, high pressure and low pressure pumps. “For those doing hybrid irrigation systems with overhead and drip, talk to your irrigation expert to size everything appropriately,” he said. “For new farms, the irrigation source might suggest a larger pump than what you need now to avoid having to purchase another pump in several years. Get a pump that’s sized for the future, not just what you need today.”

While many farmers are interested in solar-powered pumps, Hardy said it’s difficult to find a solar pump that can efficiently move the volume of water needed for drip – roughly 30 gallons/minute to the acre with enough pressure to clean the water through a filter.

“You can get a pump to cover a quarter-acre at a time, but for a larger farm, you don’t want to have to move valves all the time to get solar for a quarter-acre,” he said. “Most drip systems run 10 to 12 psi. The tank has to be nearby just to get that pressure, and water won’t travel evenly through more than 100 feet of drip tape. There’ll be a lot of good crop right next to the barrel and at the end of the row you won’t have anything.” He suggested growers choose solar if it’s the only option.

One key to successful irrigation with surface water is pump placement. “Float the suction with a marine float, a ball or an inner tube,” said Hardy. “If it’s shallow, use a milk crate to keep the foot valve off the bottom of the pond yet out of the top – about eight to 12 inches deep so it’s in cleaner water.”

Proper placement and suction setup can save time cleaning filters. “If you have a lot of surface algae, put a garden hose in to shoot water across the top of the foot valve to move surface algae out of the way to improve the cleanliness of water being sucked into the foot valve,” said Hardy. “The little bit of turbulence blowing that stuff away makes the system run much better.”

Water filtration is another irrigation consideration. For those using drip systems, the typical filtration requirement is 150 mesh. “You can achieve filtration multiple different ways – a screen filter, sand filter, disc filter,” said Hardy. “If you plug a sand filter, you have to open the bottom of the tank and flush the sand out. It’s time-consuming and strenuous, and you must put custom-graded silica sand back in. If you plug a disc filter, just take the cartridge out, hit it with a pressure washer and put it back in.”

Fertigation injector options include electric motor pumps, Venturi injectors that work via pressure differential or smaller scale piston pumps. Injector types are based on flow rate range – water per acre.

Hardy added that the irrigation plan includes both large and small fields, and growers should work with their dealer to create a plan that includes the appropriately sized injectors. “An improperly sized injector isn’t going to work and you’ll be frustrated,” he said, “and you might need different injectors for each field.”

On some farms, the existing irrigation setup includes aluminum pipes that have been in place for years. The system has likely paid for itself but is inconvenient because it can’t be driven on. Hardy said this problem can be solved by replacing sections of aluminum pipe with blue lay flat hose in vehicle traffic areas.

Hardy said an irrigation plan involves timeliness for watering crops and timeliness for repairs. “When something breaks, watering is already behind,” he said. “Prepare yourself to meet the timing schedule and get water to plants when they need it.”

by Sally Colby