In a dramatic, last-minute vote, the Maryland General Assmbly completed its 1979 session tonight by approving legislation to extend another $6 million in property tax credits to low-income home-owners.

Just two hours before the midnight adjournment deadline, passage of the new tax program was jeopardized by the Senate's refusal to accept the House measure limiting the benefits to homeowners earning less than $16,000 a year.

"This bill is like throwing bird seed around the State of Maryland," said Sen. Frank Kelly, a Baltimore County Democrat who helped lead the fight against the House bill. "All we're trying to do is help the little guy who sends us down here."

But with seven minutes remaining, the Senate was willing to give up its earlier insistence that the tax credits be extended to middle-class homeowners.

The approval of the tax relief measure came at the end of a tumultuous last day of the 90-day session during which the $150 million capital budget was temporarily held captive by a dispute over a bill increasing truck weights allowable on state roads.

The threat of extending the session at least one day was so strong that by 6 p.m. Gov. Harry R. Hughes had his aides draft a proclamation permitting the extension.

But shortly after the dinner hour, Del. John Hargreaves (D-Caroline), the chairman of the powerful House Appropriations Committee, agreed to sign the capital budget compromise even though his cherished truck weights bill had not been passed by the Senate.

The death of the truck weights bill may have, in fact, been hastened by the actions of the two men who were its strongest advocates-Hargreaves and Hughes. Hargreaves infuriated Sen. Victor Cushwa (D-Washington) during a committee session today by quickly rejecting the senator's proposal for the construction of a jail in his county.

Cushwa, who had vigorously supported truck weights legialation in the past, reversed himself tonight and voted to continue the filibuster that assured the bill's defeat.

Hughes, meanwhile, provoked the opposition of one Baltimore City senator-who said he had been inclined to support the measure-by lobbying heavily for the bill today. "I have waves of deja vu of previous administrations," said Sen. Julian Lapides (D-Baltimore).

Only two weeks ago, Lapides had dubbed Hughes "Harry The Good," but tonight he was comparing the governor's tactics to those of his (Hughes) predecessor, Marvin Mandel.

The capital budget, which Hargreaves once threatened to hold up until the truck weights bill passed, was eventually approved by both houses about one hour before the midnight adjournment deadline.

Although the most serious prospect of a deadlock was averted, the final hours of the session were marked by extreme bitterness between the delegates and senators.

Some senators blasted Hargreaves for what they said was his attempt to hold the entire capital budget hostage for his truck weights bill. Hargreaves and the House leadership, on the other hand, attacked the Senate for attempting to push through a series of controversial bond bills at the last minute.

The capital budget, in its final form, included about $9 million for the construction of multi-service government centers in Denton, Bel Air, Centreville and Glen Burnie-a little less than half the amount originally proposed by the House Appropriations Commitee. Funds for the center in Denton, which is in committee chairman Hargreaves' own district, were cut back more than for any other.

The Senate and the House also agreed to a $62 million bond bill for school construction and a $7.7 bond bill for a home financing program for lower-income residents of Maryland.

The compromise on the capital budget was reached after Hughes intervened and suggested that the multi-service center funding be cut in half this year. Hughes agreed to support funding for the entire program in next year's capital budget.

The debate over whether to fund the multi-service centers or the school construction and home financing programs was only one of the disagreements holding up the capital budget during the final day, however.

Earlier in the afternoon a group of rural senators began a short-lived filibuster against a $6.7 million bill to aid local police forces-a bill which, they claimed, gave a disproportionate share of money to Baltimore city.

The bill died in the sessions closing moments as the House refused to approve an amendment which would have changed the formula to increase 'he counties, share at the expense of Baltimore city.

In the Senate, a measure to authorize the state to give the Baltimore Orioles' baseball team $2.5 million to cover expected operating deficits over the next five years was allowed to die before it could come up for a final vote.

The Senate also killed a measure which would have given $8 million to the state's subdivisions to pay for the acquisition of parkland.

The session's final moments, were marked by legislators' frantically crossing back and forth between the two chambes seeking support for their own pet bills-a stark contrast to the generally smooth and predictable operation of the legislature over the past 90 days.

At one point early in the day when rural senators were mounting their filibuster on the police aid bill, a dozen senators were on their feet clutching their red rulebooks and clamoring for recognition.

A number of local measures died quietly in the last hectic hours of the session. Despite heavy lobbying from county government and school officials, the Prince George's County Senate delegation, on a 4-to-4 vote, killed a bill county officials say is needed to remove a legal obstacle which prevents the county from issuing bonds.

This vote puts in jeopardy an $8 million bond issue the county had planned to float in June to pay for improvements to schools, roads and hospitals. CAPTION: Picture, Del. John Hargreaves checks the board during closing hours of the Md. General Assembly. Photos by Fred Sweets for the Washington Post