NATICK, Mass. -- If Don Holman has his way, the Navy could soon be producing its own vegetarian subs, so to speak.Holman, an engineering technician with the Joint Foodservice and Engineering Team at the Army Natick Soldier Research, Development and Engineering Center, has spent the past year testing the feasibility of growing fruits and vegetables on U.S. warships. His "hydroponic farm," which uses nutrient enriched water, and no soil, resides in a 40-by-8-foot repurposed refrigerated shipping container behind Combat Feeding.The climate-controlled space is illuminated with LED lights to make it a 24-hour operation that simulates daytime and nighttime conditions and accelerates plant growth. In the first phase of testing, Holman grew dozens of different plants."We tested 83 different varieties of plants, including vegetables and fruits -- everything from strawberries to zucchini, beans and rhubarb -- a little bit of everything," Holman said. "About 51 of those 83 that we tried grew well in hydroponic conditions. The whole concept was to grow a salad for the submariners."Leafy green vegetables did particularly well, but plants requiring more sun and heat, such as tomatoes, struggled."It does grow root vegetables pretty well, other than they come out a little bit smaller, shorter, because of the way that they grow," said Holman, referring to carrots and radishes.Holman must issue a technical report by September for the Naval Undersea Warfare Center and the Navy Supply Systems Command that will help those organizations decide what, if any, fresh produce can be successfully grown at sea. Holman, who grew up on a Michigan farm and spent 30 years in the Navy, fully understands how fresh food can boost the morale of sailors on long deployments."That's what the sailors want. That's what they ask for," Holman said. "Whenever you have a happy sailor, you have a productive sailor."Several weeks into the second phase of testing, Holman is studying the yields of plants that fared well initially to see if subs can produce a sufficient amount to sustain their crews.According to Holman, the hydroponic farm has performed well over the past year."We've made modifications to the farm itself," Holman said. "We've made small changes just to kind of tweak things, [make it] operate better for us."Based on what he's observed, the former sailor said he thinks it's feasible to grow fruit and vegetables on a submarine."The No. 1 hurdle that they're going to have is space," Holman said. "Obviously, they're not putting this particular container on a submarine. They're going to have to identify a space and design a farm to fit in it."Planting seeds before a deployment would be best, Holman added."That would make great sense because it takes nine weeks to get to a [lettuce] harvest," Holman said. "So, if they started nine weeks prior to casting off, they would be able to have salads right away on through their entire deployment."Does Holman see farming in the Navy's future?"I would hope so," Holman said. "I think this makes a lot of sense for the Navy, but also for the Army and the Marine Corps in the field."