General merchandise trade deficits for the first half of this year at the regional ports of Baltimore and Norfolk dramatically reflect the trend toward an expanding national trade imbalance.

According to recent figures reported by the Maryland Port Administration, the deficit in Baltimore's general merchandise cargo at the end of the first half of the year reached 434,000 short tons, compared with a surplus of 207,000 short tons for the same period in 1983.

Baltimore, which until this year had been a net exporter of general merchandise, saw exports fall 12.9 percent from the first half of 1983, while imports rose 58.9 percent.

"We are way down in exports , and that is a good example of what the dollar is doing," said MPA spokesman Donald Klein. The strength of the dollar has made American goods more costly abroad and encouraged imports of relatively cheaper foreign-made goods.

Norfolk showed a similar, though less dramatic, turnaround in general merchandise trade for the first half of this year. The port's deficit climbed to 63,000 short tons, compared with a surplus of 11,000 short tons during the same period in 1983. Exports were down 4.8 percent, while imports were up 11.6 percent for the first half of this year.

Norfolk, which does only about 5 percent of its shipping in general merchandise cargo, also has seen a dramatic decline in its bulk commodity exports.

Although general merchandise cargo -- which includes most manufactured goods -- accounts for a small percent of the total tonnage moving through both Baltimore and Norfolk, it is used as a measure of trade deficits.

The trade deficit figures reported by the MPA for Maryland and Virginia ignore bulk cargo, including commodities such as petroleum and minerals on the import side and coal and grain on the export side, MPA's James E. Hobson explained, because trade in these commodities "doesn't flow with the changing economies of the world." Nor does trade in bulk cargo respond as quickly as general merchandise to the changing value of the dollar.

Port officials said the trade deficits are not a cause for their concern as long as the ports operate at capacity. For both Baltimore and Norfolk, the decline in exports has been offset by the increase in imports and commodity shipments.

In fact, at Hampton Roads, which includes the ports of Newport News and Chesapeake as well as Norfolk, overall tonnage is up over last year and the port is operating close to its capacity in general cargo, according to Virginia Port Authority spokesman Phillip Newswanger. The main cause of this increase, according to Newswanger, is the steady increase in general merchandise imports.

In addition to its importance in measuring trade deficits, general merchandise cargo brings the port and its surrounding community many times more income than does bulk cargo. For example, the economic spinoff of general merchandise cargo for the port of Hampton Roads recently was reported to be between $120.62 and $152.82 per ton, compared with $23.78 per ton for bulk cargo.

The principal reasons for general merchandise's greater value, according to Newswanger, are threefold: handling general merchandise is more labor intensive than handling bulk cargo; general merchandise cargo has a high value and is handled in low volume compared with bulk cargo, and general merchandise is shipped through state-run piers while bulk is handled by private operators.

Competition between the ports, especially for general cargo, is fierce, said Newswanger, who cites his port's recent success in attracting two container lines -- Neptune Orient Lines and Orient Overseas Container lines -- that previously docked at Baltimore.

To attract more trade and remain competitive with other ports, both Norfolk and Baltimore will have to make the most attractive offers to their principal customers: the motor carriers, the railroad lines and the steamship lines, Newswanger explained.