Although the popular image of India is a land of starving masses, starvation is an erratic phenomenon here.

Right now, just about no one is starving. India is fat with stocks of food grains. If anything, there's more grain around then there is space to store it.

The agricultrue ministry claims a stock of 18 million tons with another 3 million tons expected this year. During a visit to this country the bead of the Food and Agriculture Organization even proposed that the government make one to two million tons of its surplus available to less fortunate naions, hike Bangladesh.

But recent history has shown that the fat years often come to a sudden and brutal halt. In 1972, for instance, when the country was celebrating its 25th year of independence from Britain, there was more than 9 million tons of grain in stock and the government was offering "miracle rice" seeds to the North Vietnam.

Then the monsoon failed and within weeks peasants who suffer from malnutrition in the best of times began dying. By February, 1973, the storehouses were empty.

At first glance, today's picture is considerably brighter. Buffer stocks are about twice what they were five years ago. But since then, the population has risen from 555 million to 620 million.

And the official claim of an 18 million-ton stock in widely disputed. Some agriculture experts believe 4 million tons have already been lost to rot and rats.

No one prepared to say how long the stocks would last in the event of a major crop failure in the next year or two. Some specialist believe that about 2 million tons a month would have to be drawn off to avert starvation among the poorest Indians.

And these are people who wven today get 200 calories a day less than the internationally accepted minimum of 2,000. So there isn't much slack.

In a time of plenty, when there's more grain than storage space, enough inexpensive food circulates through the network of government ration shops and in the open market to provide most people with at least a subsistence food supply.

But variety of factors limit supplies to the subistence level. For one, all too many Indians simply cannot afford too many adequate food, whether at subsidized rates in the ration shops or at competitive prices in the bazaars.

Secondly, the government doesn't flood the market with enough grain to overcome the widespread malnutrition. To do so would force the commercial grain price down and invite the bitterness of farmers and middlemen.

A third problem is that the specter of famine is never far from the minds of India's leaders. So there's always the tendency to build hugh stocks. Whenever starcation strikes, it is grim reminder that despite its impressive gains in a variety of fields, India is never too far from desperation in feeding itself.

The reasons for this area basic and judged on available evidence perhaps insoluble:

The pressure of population means that each year the food grain crop must increase by 2.5 million tons.

35,000 more people every day means shrinking arable land and smaller and less efficient family farms.

The high cost of oil products and electrical power means that critically needed critically needed irrigation is lagging far behind demand.

Until irrigation is expanded so that most farmland is not entirely subject to rainfall and double and triple cropping becomes commonplace, experts believe that India will continue to go through recurring periods of feast, so to speak, and famine.

As one western agriculture specialist stated, arable land is now reaching its limits and food supply is barely keeping up with population growth. A glance at comparisons in grain output between the United States where much of it goes for animal feed, and India, where it is consumed directly by humans, is revealing:

In the United States, with a population one-third that of India's, 472 million acres are planted in various crops. The total in India is 452 million acres.

An acre of rice land in the United States yields 3,234 pounds of rice, while in India the yields is one-third that. One acre of a U.S. wheat field produces 30.3 bushels. An Indian field yields three bushels less.

Although the so-called green revolution of "miracle " strains of wheat and rice have made a significant difference in India's overall grain output, initial gains are flagging.

And then there's the irrigation problems. In 1976 the southwest monsoon turned desultory. Some parts of the vital rice-growing regions burned with drought while elsewhere floods washed out freshly planted green shoots. Output dropped by 100 per cent.

During the marketing year which ended four months ago, the government imported 5.2 million tons wheat, 3.4 million tons of it from the United States. Rice imports for the same period were 100,000 tons.

The new government of Prime Minister Moraji Desai has taken some steps that foreign agriculture experts believe will be helpful in the immediate future. One of the more important has been to eliminate restrictions on the movement of wheat between states. This is expected to even out the situation of glut in one area and shortage in another.

But, ultimately, even the most optimistic specialist consur that unless the conflicting pressures of too many people and too little land are eased, the periods of feasts must fall behind the famines.