TRACTOR sales fell 47% in in December compared to the same month in l997, with only 165 units sold, the South African Agricultural Machinery Association announced on Monday. Tractor sales for the year were down 30% on the previous year, at 4015 units. Combine harvester and baler sales for 1998 were also 30% down on 1997 sales. The association said that, while the summer crops look good at present, the maize crop is approaching a critical phase and will require rain within six weeks.