Moscow — Once again, the Soviet Union is facing another dismal harvest. From the Ukraine come reports of a disappointing wheat crop - prompting the United States government to adjust its forecast of Soviet grain production downward to 170 million tons. If correct, that would mean a drop of 25 million tons from last year. (The Soviet government itself no longer publishes grain production figures, probably because they embarrass the Kremlin leadership.)
From the southern Soviet republics comes news that the fruit and vegetable harvest is also disappointing - probably indicating that Soviet shoppers will have a hard time finding such products this winter.
The supply of beef, chicken, and eggs is expected to be relatively good, however. But that must come as cold comfort to Moscow, which is now forced to spend vast amounts of precious hard currency on food imports for yet another year.
So concerned is the ruling Communist Party that its Central Committee has reportedly been called to a special meeting later this month - called an ''extraordinary plenum'' - to consider solutions to the country's myriad agricultural problems.
It is rumored, too, that the same meeting may well consider changes in the country's political leadership - perhaps even reaching to the ruling Communist Party Politburo.
The party is likely to consider many of the same agricultural ''reforms'' that have been alternately embraced and jettisoned over past decades - all apparently without much success. Even now, it appears that it will be impossible for the government to meet its goals for many kinds of foods during the current five-year planning period, which ends in 1985.
Similarly, even with food imports, current consumption of milk and milk products, meat, fruits, and vegetables falls well short of what the government defines as a ''rational norm'' for Soviet citizens. About the only items now available in sufficient quantities, according to government figures, are fish, eggs, sugar, potatoes, and bread - hardly the foodstuffs of a balanced diet.
The figures underscore one key point: The failings of Soviet agriculture go beyond this year's poor wheat crop.
''Grain is the area that gets the attention,'' says one Western expert, ''but they're really not having much success in any of their crops.''
Unfortunately, the trends seem to point in the wrong direction. Production of some commodities - sunflower oil, potatoes, and vegetables - is not up to what it was even 10 years ago.
Clearly, such a weak showing in agriculture inevitably has political repercussions. Yet, surprisingly, it has not seemed to dampen the political fortunes of the Politburo member who supervises agriculture, Mikhail Gorbachev. He is now No. 2 in the Politburo hierarchy, and many Western analysts say he is well poised to take over the country's leadership after the current leader, Konstantin Chernenko, passes from the scene.
Indeed, there have been numerous rumors that Chernenko's resignation is imminent - and will perhaps be announced at the coming plenum. Some analysts say that is far-fetched. But the fact that such rumors are circulating, some Kremlin-watchers say, indicates at least a degree of friction in the ruling circles of the Communist Party. One ranking Western diplomat speculates the rumors were planted ''by those in the Gorbachev camp.''
However, it remains unclear just what Gorbachev, Chernenko - or anyone else, for that matter - can do to improve agriculture in this country. The combination of climate and collectivism has wreaked havoc on food production here over the past six decades. While farm production in the US has soared to record levels, it has stalled and, in many cases, declined in the USSR. This country, once the world's largest wheat exporter, is this year expected to equal or exceed its record 46 million tons of grain imports.
To be sure, the Soviet Union has the weather working against it. Sixty percent of the US gets more than 28 inches of rain annually. Only 1 percent of the Soviet Union does. Most US farmland is south of the 49th parallel; two-thirds of the Soviet Union is above it. That makes for an exceptionally short growing season.
Nevertheless, climatic problems are compounded by ideological ones: the stress on collective and state-run farms, and the complicated government bureacracy. One Western diplomat says that, even now, huge mounds of sugar beets are lying in fields in the Ukraine, since there is no transport available to take them to storage - and there are limited storage facilities for them anyway.
The party has tried to combat such problems by forming new committees to coordinate the activities of government ministries at the regional level - apparently with some success.
One strategy currently in vogue is the so-called ''collective contract,'' which allows teams of workers greater flexibility in tackling farm chores - and in splitting up wages and bonuses. But, as one diplomat notes, ''That's not a new idea.''
Meanwhile, the government has also gradually raised the prices it pays for farm products (to encourage production) yet has held retail prices the same. The result: spiraling agricultural subsidies.
Still, it's unlikely that any among the country's current political leadership want to tackle the thorny problem of raising prices - especially if, as many Western analysts say, there is a great deal of uncertainty and lack of strong guidance in the ruling Politburo.