A problem as old as Adam and Eve is plaguing the Army.

The military calls it "sex fraternization"-socializing, and more, between male and female soldiers of different ranks. And the Army wants it stopped. Particularly as more women join what used to be called "this man's Army."

"It's kind of hard for the sergeant to order Mary to scrub out the latrine the next morning when they were sleeping together upstairs the night before," one Aryy legal officer explained.

"It's bad for discipline."

Army headquarters last month declared war on what a May study called "a creeping advance of sex fraternization throughout the Army," undermining discipline discipline, authority and morale. The report included "socialization, courting and marriage" as examples.

When Army Staff Sgt. Darryl Stewart kissed and had sex last spring with a female recruit he was engaged to marry, Fort Jackson officials court-martialed him, busted him one rank and fined him $500.

His fiance, Pvt. Cheryl Barnard, got 30 days restrictions on base, 30 days extra duty and a $150 fine from an administrative board. She complained she was a "scapegoat for everybody."

"A lot of girls. . . are fooling around with frill sergeants and trainees, and they are laughing behind my back because since all the attentionis on me, they are getting away with all kinds of things," she said at the time. "I believe the whole company is messing around."

The November anti-fraternization directive did not specifically prohibit anything, but instructed commanders to "counsel those involved or take other actions as appropriate." The other services have issued nothing similar.

The Army directive and previous individual base reuglations anger some officers and enlisted persons who say the fraternization rules violate First Amendment guarantees of freedom of association-as well as the laws of nature.

"I love her and I love the Army," Sgt. Stewart, a college graduate with 10 decorations and awards, said at his court-martial. "I feel [the regulations] conflict with personal interests."

"How can you legislate romance?" asked Col, Mae Pomeroy, Fort Jackson's spokeswoman. "That's a real toughie."

There are about 49,000 female officers and enlisted persons in the Army. That's up from 12,400 in 1972, when the Army launched a concerted effort to recruit women. The Army's total strength is about 760,000.

Although the Army wants to restrict fraternization at all ranks, it is particulary concerned about what it considers compromising activities during basic training.

That makes the fraternization policy especially controversial at Fort Jackson, the Army's largest recruit training base and one of only three in the country that trains female recruits. The others are Fort Dix, N.J., and Fort McClellan, Ala.

Since there are only 96 female drill sergeants for what is at present 1,958 female recruits at Fort Jackson, some of the 581 male drill sergeants have to train female platoons. There are 5,059 male recruits.

"The fraternization rule is a very big bone of contention among NCOs [noncommissioned officers, including drill sergeants] on the base," said a senior legal officer who asked that his name not be used. "They're very unhappy about it."

A base regulation psohibits "any nonprofessional, social relationship of a personal nature between any permanent party [Army] personnel and a trainee. . . outside of a duty mission." It specifically bans drinking, dating, grambling and sex.

Legal officers say NCOs usually are more severely punished than recruits in fraternization cases, but say that's because NCOs should know better. They point out that fraternization rules protect NCOs and officers from blackmail, as well as prevent instructors from taking advantage of recruits or showing favoritism.

"The thing is, the rules have got to be applied with common sense, that's the most important thing," the senior officer said. He said only"the most serious cases" are prosecuted.

But some sergeants have been convicted of nothing ore serious than dancing, kissing and hugging. Their sentences sometimes compare with those of two drill sergeants convicted this month in connection with the June 29 heat stroke death of a first-day recruit who died after strenuous exercise.

In that case, Sgt. 1st Class Lawrence Chapman Jr. was demoted one rank and fined $500; Sgt. Willie Alexander was sentenced to six months in prison, loss of two-thirds pay for six months and reduction to private.

There have been at least six courts-martial of Fort Jackson soldiers for fraternization in the past two years, including the April 1977 case of Drill Sgt. Richard Getty, sentenced to a month in prison and a bad conduct discharge for having sex with recruits.

In a court-martial last April, 1st Sgt. Max Howerter was convicted of two counts of kissing and hugging a female trainee and letting her sit on his lap in front of other recruits at a Columbia bar. Howerter, a highly decorated 18-year veteran, was reprimanded and fined $1,200. He said he had been engaged to the woman for more than six months.

The Army says it doesn't know how many sex fraternization courts-martial it has had. Figures are also not available for soldiers disciplined outside courts-martial.

However in one case that did not involve a court-martial, a Fort Jackson administrative board fined Sgt. 1st Class Rodney Congdon half a month's pay in 1976 for "dancing and socializing" with a trainee. In another administrative action a staff sergeant was demoted in February for charges including marrying a trainee.

Fraternization policies are nothing new to the military, though most past fraternization cases dealt with officers and enlisted men. In the first reported American fraternization case, in 1825, a first lieutenant was convicted in Boston of degrading himself "as an officer and a gentleman" by going fishing and getting drunk with enlisted men. The man was also charged with pulling down another soldier's pants, bowling, embezzlement, masquerading as an enlisted man and throwing a dead cat at someone.