Will new party coalitions emerge in W. Germany's March elections?

West Germany sails into uncharted waters with its early general election March 6. At issue are:

* ''Ungovernability.''

* The threatened demise of the small Liberal Party and the birth of a nationwide ecology party.

* West German support for the NATO ''two-track'' negotiate-but-deploy missile decision.

* Adjustment to recession-reduced social welfare.

The way to the new election almost two years before the scheduled 1984 vote was opened with President Karl Carstens' dissolution of Parliament Jan. 7.

Ever since the Liberals' change of coalition partners Oct. 1 brought the ouster of Social Democratic Chancellor Helmut Schmidt, the feeling has been widespread that the new government of Conservative Chancellor Helmut Kohl must legitimize itself at the polls.

For the Liberals the March 6 election is a matter of life and death. In public opinion soundings they are substantially below the 5 percent minimum needed to get into the Bundestag - partly because their desertion of the Social Democrats left a bad taste.

The Liberals' place as the traditional majority-deciding swing party may be taken (according to opinion polls) by the Green Party, a radical environmental, antinuclear party that holds seats in six of the 11 state legislatures but has not yet made it over the 5 percent hurdle into the federal Bundestag.

If the Greens do get into Parliament, they will not, however, act as the Liberals have done in moderating the ideologues. Instead, the Greens would likely refuse any coalition with the Conservatives and probably with the Social Democrats too, while strengthening the Social Democratic left wing.

If the Greens win just enough seats to prevent either the Conservatives or the Social Democrats from gaining a majority, this would be the ''ungovernability'' dreaded by many politicians in the established parties. Dr. Kohl is universally expected to get the strongest representation in the Bundestag, but polls suggest he might not get an absolute majority if the Liberal Party vanishes.

A Green entry into the Bundestag would also strengthen the protest movement against the deployment of new NATO nuclear Euro-missiles due to begin by the end of this year if there is no prior Soviet-US arms-control agreement.

But the decisive issue in the election may turn out to be the soaring unemployment and the need to trim social welfare in a time of prolonged recession. The Kohl government has announced social welfare cuts that could be unpopular. If today's 9 percent 2.2 million unemployed rise to 2.5 million by March, voters may well blame the Conservatives.