As agricultural fairs go, the Doba version looked very much like similar gatherings elsewhere in the world with livestock, local farm products and tools on display, plus superb folk dancing to boot.

But while local boosters bragged over the weekend that this was the country's first farm fair, its real importance lay in the fact that it was held in what long had been territory controlled by southern rebels fighting Moslem President Hissene Habre's central government in Ndjamena.

Only last month a major rebel leader, Alphonse Kitoga, accepted a government amnesty offer and came in out of the bush with an important "codo," as the guerrilla groups in the Christian and animist south are known locally.

Each such success for the government strengthens Habre and weakens his adversaries in the Libyan-backed GUNT, the French acronym for the forces loyal to former president Goukouni Oueddei.

No longer does the government, located 280 miles to the northwest in Ndjamena, have to worry about a second front of southern rebels along its borders with the Central African Republic and Cameroon.

That is considered critical in the renewed fighting between government forces and the GUNT and Libyan troops in the northern desert.

The new calm also holds out hope for getting back to full farm production in the south, which is known as "useful Chad" in contrast to the desert that makes up more than half of this landlocked country's area.

In the Doba area alone, Prefect Paul Ngardoumri told visiting journalists that about 8,000 rebels from five guerrilla groups had taken advantage of a government offer to join the national Army.

But the government is taking no chances.

Northern troops, identifiable by the turbans covering most of the head and face, were much in evidence here.

Perhaps understandably, the southerners would prefer to have local troops in their place.

Yet if the main local guerrilla groups -- with names like "The Blacks," "13" and "The Bee," have come over to the government, total calm has not been restored.

Recently, government troops were ambushed little more than 20 miles outside Doba. The area around Moundou, 50 miles west of here, is considered so insecure that military escorts accompany convoys of civilian cars.

The prefect, a 34-year-old Doba native who spent 10 years studying agricultural engineering in France, said he had devoted a great deal of time and effort in coaxing rebels out of the bush since he was appointed to his present job last August.

The government's credibility was such, he said, that farmers are now volunteering information about the remaining rebels, many of whom were described by local residents as little more than armed highwaymen.

Local residents, who were less convinced about government charges of Libyan influence in the guerrilla groups, said the terrible days of 1984, when government troops tended to inflict mass reprisals on villagers, were now a thing of the past.

The prefect said that under terms of a recent agreement joint commissions of government and ex-guerrilla representatives investigate each incident in order to avoid reprisals.

If the renewed fighting in the Sahara to the north has heightened fears that the country is still not at the end of its now more than 20-year-old series of wars, the prefect and farmers indicated that they hoped to go back to farming.

The prefect spoke enthusiastically about doubling the acreage devoted to cotton, Chad's main foreign exchange earner.

He likewise made no secret of his desire to quit the prefecture and go back to his job as an agricultural engineer "before I get even more gray hairs in my beard."