HOW MUCH CAN we rely on voluntary activity to replace the services lost by federal budget cuts? A new Gallup poll, sponsored by a national coalition of voluntary agencies, provides some evidence.

Most people, it appears, do some sort of unpaid work. Over half of adults and teen-agers report recent voluntary activity--although when you weed out the occasional helpers and the people who take credit for feeding their neighbor's cat, that number drops to about 30 percent. Still, that's a lot of people, and if you could persuade them to step up their hours a bit, you might be on to something. What sorts of activities do these people seem willing and able to do?

The largest category of activity--occupying almost one-fifth of the population--is religious. Most of this time is spent in ushering, choir singing, Sunday school teaching and fund raising. Another big interest is education, primarily PTA and school board activities and room-mothering. Health related activities, primarily fund raising but also helping out in hospitals and nursing homes, are also popular. Next on the list are recreation, citizenship, politics and work-related activities.

What is most noticeable about these choices is that they involve things that people do for themselves, their families or their immediate neighbors. Less than 5 percent report any "social welfare" activity even broadly defined. In other words, the kind of volunteer activity that most people do is a far cry from the day-to-day drudgery that is bought with government money. It's one thing to bake brownies, address envelopes or wheel a bookmobile down a hospital corridor, and quite another to show up regularly to tend to the needs of the troubled and afflicted. Many of the poor and sick, after all, live in perfectly wretched neighborhoods, live rather disorderly lives and may even forget to say thank you.

There is also the question of time. Women make up the bulk of volunteers; men outnumber them only in recreational and work-related activities. An increasing number of women, however, have paid jobs as well. With volunteer activities already occupying a good part of their free time, the potential for expansion is limited.

Voluntary activity is, and always has been, an important and commendable part of American life. Certainly it should be encouraged to expand beyond its present horizons. But voluntarism never did suffice to erase the horrors of the almshouse or the sweatshop. Government got into the social welfare business because, before it did, most of the very poor, the mentally ill and other near helpless people lived in truly wretched conditions--conditions that have no place in a prosperous nation such as ours.