A Utah State University plant scientist said a farm of only 13 square meters - about the size of his office - could grow enough wheat to keep one person alive indefinitely in space.

Frank B. Salisbury, a member of NASA's Aeromedical Advisory Committee, thinks the United States should establish a moon colony and be heading for Mars "as soon as we can" - within the next 20 years at least."There are benefits to be expected from such exploration; there may be key minerals or such things. Spinoffs could be most important," he said.

Salisbury and his colleague, Bruce Bugbee of USU, who has a NASA grant for the work, have grown, in a controlled environment similar to what would be found in space, five times the world record yield of wheat, Salisbury said.

Working in a NASA project called Controlled Ecological Life Support System, they achieved sustained yields of 60 grams per square meter per day of edible wheat. Their project, funded by NASA in 1981, has been a great success, Salisbury said.

Its purpose is to establish the controlled environment for growing plants to purify the atmosphere and produce food.

A controlled environment wheat farm would be a little easier to do on Mars than it would on the moon because the length of Mars' day is about the same as Earth's and there is a little atmosphere that would help protect against radiation, Salisbury said.

"There is lots of carbon dioxide in the Mars atmosphere and that's a big plus. For the moon, we'd have to bring all the carbon from Earth to put in the atmosphere and grow plants."

The idea of growing plants to purify the air and feed astronauts or colonists becomes more important with longer-term space travel, Salisbury pointed out. "For up to two years, you can pretty well take the food you need. But if you go long enough, it begins to really pay off to recycle wastes and produce food by growing plants."

The USU professor was on an ad hoc committee that compiled for NASA a list of desirable plants for possible growing in space.

He chose to work with wheat, which was on the list, "because two top notch wheat breeders, Wade Dewey and Rulon Albrechtsen of USU, were right across the hall from me. It was a good choice. It is easy to eat the grain, to prepare it in a lot of different ways and wheat is a very efficient plant."

The nearly vertical leaves of wheat and other grasses are very efficient, so light rays coming in parallel are bright enough to make the plants efficient photosynthesizers, but never too bright.

Wheat can approach the theoretical limits of productivity, which would be about 12 to 15 percent of light energy converted to food energy.

"We can get about 10 percent, so far, and that's pretty impressive. In the field, out in nature, it's less than 1 percent," he said.

The USU project, for which Bugbee is now the principal investigator, was initiated in 1981 when Bugbee was hired as a postdoctoral fellow.

Recently, Salisbury and Bugbee had a flight experiment accepted for definition studies. Their proposal was one of 28 accepted from among about 200 submitted to NASA in 1984.

"Eventually we are going to get there and look at the effects of weightlessness on a number of things, but mostly on the photosynthetic processes. We'll see how much yield we can get in weightlessness."

The United States has done only a few such experiments, but the Soviets have done many more, he said.

"So far as I know, no one has really studied respiration and photosynthesis in space and weightlessness. We'll emphasize that and look at other things such as how the (wheat) heads will develop. We have a series of seven or eight experiments that could go, but we have to go through the definition study first, and that will take three or four years," he added.