September 28, 1986

FRANK ARIES has developed the uncanny knack of buying up huge tracts of land around growing metropolises at just the right time. This time he may have struck it particularly big. Last year, the 52-year-old developer came here to buy 1,400 acres of a cattle ranch owned by the Mobil Corporation and acquired 20,483 acres for $92.5 million. This month he bought 3,000 more acres from Mobil for $46 million and an additional 4,000 that includes a foreign-trade zone for $40 million, bringing a total of almost 29,000 acres under his control.

THE 99th Congress heads into the homestretch this week, hoping to complete its work and leave town by Friday. But the pressure of the schedule and the threat of President Reagan's vetoes could well move the finishing post down the track. Mr. Reagan demonstrated his willingness to wield his veto pen Friday when he rejected legislation imposing stiffer economic sanctions on South Africa. Two other measures could meet the same fate this week. One provides money for most Federal operations in the fiscal year that begins Wednesday. The other reduces the Federal deficit by about $15 billion for that year.

Ronald Reagan, by dint of enormous personal popularity and adeptness at mixing Presidential power with politic flexibility, has almost always had his way in Congress. Last week, however, Mr. Reagan vetoed legislation to impose punitive sanctions on South Africa; White House aides and Republicans in Congress said it would be hard to prevent an override, the first of his Presidency.

IN a top-secret room at the Excel Corporation's huge plant here, where 5,000 head of cattle are slaughtered a day, the beef packer is carrying out an experiment that it hopes will swell its coffers and help reverse the beef industry's sagging fortunes. Inside the room a few dozen workers are cutting beef into consumer-sized portions that will be shipped to supermarkets and sold under the Excel label, making Excel the first large beef packer to market brand-named beef in a big way. The packers are hoping that the brand-name approach could do for beef sales what designer labels did for blue jeans and Frank Perdue did for chicken: create distinctions where none existed - and do so at higher prices and, presumably, higher profits. If the industry's innovators have their way, a steak will no longer be a steak; it will be a steak by Excel or IBP. Now, ''the only thing not branded in the supermarket is beef,'' said William D. Parker, vice president for meat merchandising at Kroger, one of the nation's largest food chains. ''That's one of the reasons it hasn't progressed as well as some other products.''

Life in America is likely to change in hundreds of ways under the new tax law, shifting the way people spend, save, borrow and invest their money. While the basic fabric of American life will not be radically altered, analysts say, many adjustments are certain. Even though most people will end up with more cash in their pockets to do with as they please, they will lose many of the tax benefits that have for decades helped subsidize and encourage a long list of common expenditures. Housing and Autos Some people may buy less expensive homes or forgo a vacation home because tax benefits will not provide as much of a subsidy for home ownership under a system of lower tax rates. Similarly, with rents expected to rise because of the curtailment of tax breaks for landlords, apartment dwellers may have to set their sights a bit lower unless they are willing to spend more.