Erratic monsoon rains over the subcontinent and widespread damage to crops have reduced grain production this year in India, forcing the government to abandon its claims to food self-sufficiency and reluctantly import wheat from the United States.

While the effects of damage by unseasonable rainfall in May and the late arrival of the rain-bearing monsoon winds in India's northern crop belt last month are still difficult to assess, some agricultural analysts predict a shortfall of 6 million or 7 million tons of anticipated grains after the October harvest.

Last year's grain output was 132 million tons and the government's target for this year had been 141.5 million tons.

The drop in food production hardly compares to the crippling drought of 1979, when output plummeted 22 million tons from the previous year's record of 113 million, but it has become worrisome to Indian agricultural planners and something of an embarrassment following Prime Minister Indira Gandhi's highly touted plan to make India self-sufficient in food this year.

Agriculture Ministry officials sought to put as good a face as possible on the situation, insisting that the shortfall this year would be well under 6 million tons. But they conceded that official attention to food security in India has been heightened by the unstable monsoons, resulting in a decision made quietly last week to sharply increase the country's minimum reserve stock requirement.

Moreover, an unexpected drain of about $500 million in foreign exchange because of the wheat imports, unplanned government compensation to farmers for rain-damaged crops and rising grain prices are expected to refuel India's inflation, which the government claimed had fallen to zero in March.

Since agriculture accounts for 48 percent of the national income, economists are predicting there will be some decline in the gross national product growth rate, which in real terms was put at 5 percent last year.

Three-quarters of India's farmed land is used for growing grain and two-thirds of the country's cultivable land is exclusively dependent on rainfall, meaning that failure of the monsoons is disastrous to grains and raises the specter of starvation. The government has developed stocks of grains for use, in part, in such emergencies, but problems persist in getting grain from storage areas to regions where it might be needed.

This year's rain troubles were two-fold: first, this spring when early rains fell on sown wheat before farmers could harvest it, and again when the monsoons failed to materialize in many parts of the country until late last month.

The monsoons, which normally hit the southwest coast in May and move into the northern farm belt in early July, are eagerly awaited by people all over India, not only for survival of the crops but to bring relief from the searing summer heat.

The early rainfall in the major wheat-producing states of Punjab, Haryana and Uttar Pradesh destroyed an estimated 2 million tons of wheat in the fields, but, more importantly, caused significant quality deterioration in much vaster amounts of wheat.

According to estimates of the agricultural counselor's office of the U.S. Embassy here, which closely monitors India's food production, more than 70 percent of the 4.8 million tons of wheat produced in Punjab was affected and believed to be unsuitable for storing for more than eight months.

The embassy estimated that storage loss of this year's wheat could be high unless the Indian government disposes of it quickly.

Moreover, U.S. agricultural counselors warned that the early rains will have a residual effect on next year's crop because of a shortage of quality seed as a result of the damage and because of expected delays in wheat planting caused by the late transplanting of rice in the same fields.

The sluggish monsoons have also affected coarse grain crops such as corn, barley, sorghum and millet, which are estimated to yield only 28 million tons this year, compared to 31 million tons targeted by the government.

Production of rice, a staple in India, is likely to total only 50 million tons, 8 million short of the government target and 4 million tons below last year's crop.

In the face of the production declines and an accompanying shortfall in the reserve stock of grain, the government announced earlier this month that it will purchase 2.5 million tons of wheat from the United States. In June, Agriculture Ministry officials had said it would be unnecessary to import any wheat because India had become self-sufficient.

Last year, after five years of not having to import wheat, India purchased 2.2 million tons from the United States and Australia, Agriculture Ministry officials said, to replenish reserve stocks that had been depleted by the 1979-1980 drought.

Current reserve stocks total about 15 million tons, while 18 million is considered optimum and 12 million is regarded as a minimum safe level. Agriculture Ministry sources said the government just approved an increase of the minimum reserve stocks to about 21 million tons, which in turn will create an even greater shortfall of grains available for current use.

K. C. S. Acharya, under secretary of agriculture, said the purpose of the U.S. grain deal was to replenish the reserve stocks, not only as insurance against future crop failures, but also to hold down prices.

"Such behavior in the monsoons tends to generate an alarmist psychology, as large as India is and as concerned about food security. It has a sobering effect on the market," Achwrya said in an interview.

He conceded that there was a symbolic aspect to importing grain in a year proclaimed by the government as a food self-sufficient one, but he said the decision was taken at the "highest level," adding, "When it comes to food, there is no difficulty in doing that. No civilized government will allow starvation to take place, or jeopardize its reserve of food."