On Poland's private farms, aid from Western churches will mean more than Marx

Driving through this south Polish countryside and watching farmers, many of them elderly, at work in a still horse-dominated agriculture is to realize how pressing is the need for financing for agriculture here - whatever the source.

Later this year, the private farms of Poland may begin to receive such help from a planned agricultural development fund run not by the government and not by the Communist Party - but by the Roman Catholic Church.

Private peasant farmers cultivate more than 80 percent of arable land in this predominantly Roman Catholic country. There are 4 million private farmers, and some of their holdings are no more than a hectare (about 2.5 acres). But they produce 80 percent of the nation's meat, dairy products, and fruit.

For years, despite this vital contribution, private farmers were the ''poor Cinderellas'' of Polish farming, always at the end of the line. In front of them , of course, were the big state farms.

Under economic reforms started last year, the state farms for the first time have been made responsible for making a profit and for their own financing. Private farms have been promised a bigger share of agricultural investment and equal access to inputs like fertilizer and machines.

But, like Poles in other fields of what the authorities call ''socialist renewal'' and correction of the ''errors'' of their predecessors, the peasants are taking a wait-and-see attitude.

Behind all their doubts is a longstanding misgiving about government assurances of the security of land tenure. There is a persistent suspicion that some day - even after three decades of ''free'' farming - a future Communist regime might revert to old orthodoxies of a ''socialized'' agriculture.

The private farmers are waiting for the government to follow up with specific amendments or additions to the Constitution to guarantee beyond a doubt the sacrosanct nature of private land ownership and inheritance.

More tools are reaching private farmers, but they are not coming quickly enough or in large enough quantities to encourage confidence in a genuinely better deal ahead.

Late last year, Roman Catholic bishops in West Germany initiated the plan for a fund to be channeled to the private farmers through the Polish church. Predictably, the concept did not commend itself to the Communist Party.

The original plan was for a church bank supported by the Western Roman Catholic episcopates taking part in the project. Polish authorities balked at a bank or anything that looked like charitable aid or a ''church Marshall plan.'' Gradually, however, they were brought around to accepting the usefulness of the proposal.

Shortly before Pope John Paul II arrived in mid-June for his second visit, Prime Minister Wojciech Jaruzelski told the Polish primate, Jozef Cardinal Glemp , of the government's acceptance of the concept. Moreover, it was said, the fund was to be administered by the Polish church. Later this month, Polish bishops will visit West Germany to start planning the project.

The fund's resources will be raised through Catholic churches in the West and through other Catholic institutions. The projected figure of 5 billion deutsche marks (nearly $2 billion) has been seen by some experts as overly ambitious. But , it is pointed out here, the funds are to be spread over five years.

The most likely forms will probably be credits to farmers to buy farm tools or other items they most need. In the case of machinery or spare parts not available here, the fund will be able to make purchases abroad for sale to the farmers on long-term credit.

The government's decision to allow this kind of undertaking is almost as striking an illustration that the party and government here recognize the ''need of the church'' - as a senior churchman here put it - as was the decision to allow a visit by the Pope last month.

The fund will have to meet some strict legal requirements that Polish authorities will certainly put up. But it is thought that the fund can be in operation by the end of the year.