Agriculture Secretary John R. Block, conceding that the administration's early proposals to cut farm-program spending were too harsh, said yesterday that the pending Republican budget compromise will provide additional help for the troubled farm economy.

The fine print of the White House-Senate GOP agreement has been closely guarded, but it apparently implies a substantial administration retreat on not just the budget but on some of its proposals to restructure basic farm programs starting this year.

Block told reporters yesterday that previous Reagan administration proposals sought to change farm policy more quickly than the farm situation could tolerate.

"Given the way the situation's deteriorated in rural America, it was looking more austere every day, and it looked like some adjustment was appropriate," Block said. "The adjustment's been made."

The administration's budget and farm-bill proposals drew strong resistance from farm-state Republicans, who urged the administration to back away from its plans to cut price-support loan rates and direct subsidies to farmers. House farm-state Republicans told the White House before the Easter recess that the Reagan plan was dead and that they would offer alternative farm legislation.

Block said yesterday that while the GOP budget compromise would provide more money to ease agriculture's transition to the more "market-oriented" system the administration wants, it means "no change in philosophy, policy or objective."

Sources said the compromise envisions leaving both crop-loan rates and so-called target prices at current levels next year. The target prices are the basis for government supplemental-income payments to farmers. But more than $1 billion would be saved by capping the subsidy payments to individual farmers at $25,000.

Current farm law limits individual "deficiency payments" to $50,000. These payments go to producers of major grains, rice and cotton and are intended to make up the difference between low market prices and production costs.

But Agriculture Department statistics indicate that most of the payments go to farmers in the highest income categories.

Since the recent GOP budget agreement, Block has pointed to the availability of an additional $8 billion for farm commodity programs over the next three years as a plus for the hard-pressed farm economy.