Marriott Corp. yesterday reported a 34 percent first quarter profit, but announced it was cutting some food production at its Fairfield Farms Kitchens putting about 150 people out of work.

The Prince Georges County unit has been one of the largest private employers of blacks in the D.C. area.

Marriott reported a turnaround in the previously distressed airline food catering operations and a continued boom in its hotel operations during the January-march period.

But earnings were reduced by approximately $1 million, or a penny a share, due to losses and reserves reated to the company's decision to curtail some food production operations.

Marriott spokeswoman Barbara Van Blarcum said 150 jobs of the Fairfield Farm Kitchens' 500-person work force were eliminated by shutting down a bakery and several smaller operations that formerly produced products for other companies in food services.

"It was part of a cost-effectiveness situation . . . we will continue some items (and) . . . expect to recover the losses and reserves in less than a year," Van Blarcum added.She said the company has been seeking to relocated the workers affected in other jobs at Marriott divisions.

Bethesda-based Marriott, a world-wide restaurant, hotel and food services firm, reported that first-quarter earnings totaled $11.8 million (31 cents a share) compared with $8.8 million (23 cents) in the 1978 period. Sales rose 21 percent to $303 million.

President J. W. Marriott Jr. said the recent 12-week increase extends a trend in gains of 30 percent or more, recorded since mid-1978. He noted "continued strength in our hotel business" and said "it is singificant that we can move the company along like this despite serious inflation in labor and food costs."

For all of 1979, he predicted that Marriott Corp. should exceed a 10-year compound profit growth rate of 21 percent. "advance bookings in our hotels show no sign of a recession near-term . . . it looks like another very good year," Marriott added.

More than 2,800 rooms have been added to the Marriott hotel system since last year and first-quarter average occupancy led the industry at more than 80 percent. Hotel sales and profits jumped by about a third in the recent period.

Food service contract volume advanced 22 percent and domestic air-line catering profits rose after several declining quarters. Restaurant profit margins sagged, however, as Marriott had forecast earlier. Although sales rose 12 percent, profits declined 40 percent; with a return of milder weather, Marriott said profitability began ot improve as the quarter ended.

Federal National Mortgage Association, which supports a secondary market for home mortgages, said soaring interest casts reduced first-quarter profits to $39.5 million (65 cents a share) from $52 million (87 cents) last year.

The Washington form, known as Fannie Mae, said it earned $64.1 million on its mortgage portfolio in the recent quarter compared with $72.4 million a year earlier, An increase in the portfolio yield was more than offset by higher costs to Fannie Mae of borrowing money to support its mortgage activities.

Fees related to issuing mortgage purchase commitments declined sharply, to $7.5 million from nearly $28 million in the 1978 period.

The decline in fee income reflects a decrease in the level of Fannie Mae mortgage originations but-because of earlier commitments-actual mortgage purchases were a record $3.7 billion compared with $2.4 billion a year ago and $2.9 billion in the final three months of 1978, the company stated.

National Bank of Washington, third largest of D.C.'s commercial banks, reported that first-quarter earnings were at the same level as last yaer: $1.4 million ($1.25 share) for both periods. Loan volume increased to $469 million from $428 million.

Madison National Bank of Washington reported that first-quarter earnings rose 30 percent to $423,393 ($1.10 a share) compared with $325,734 (85 cents) in the 1978 period. Loan volume rose $14 million to $82 million while deposits increased $16 million to $116 million.

Scientific time Sharing Corp., a Bethesda supplier of remote computing services, reported profits in the nine months ended Feb. 28 fell to $687,000 (44 cents a share) from $745,000 (51 cents) a year earlier. Revenues rose 24 percent to $12 million from $9.7 million. Investments in a European expansion cut into earnings during the past nine months, President Daniel Dyer stated.

Manor Care Inc., a Silver Spring nursing home company, reported earnings in the nine months ended Feb. 28 of $1.9 million compared with $1.5 million a year earlier, or 91 cents a share in bothe periods with more shares now outstanding. Revenues rose to $34.5 million from $26.7 million. Earnings for the recent nine months include $1.4 million (79 cents a share) from an equity investment in Hillhaven Corp., the Silver Spring firm said.