data one;
  input variety fert yield;
  cards;
1 1 37
1 1 40
1 1 41
1 1 39
1 2 47
1 2 45
1 2 42
1 2 46
2 1 40
2 1 43
2 1 47
2 1 42
2 2 37
2 2 47
2 2 41
2 2 43
3 1 51
3 1 56
3 1 52
3 1 45
3 2 41
3 2 45
3 2 42
3 2 47
;

proc glm;
  class variety fert;
  model yield=variety fert variety*fert / solution clparm;
  lsmeans variety*fert / slice=variety;
  estimate 'Fert 1 - Fert 2 for Variety 1' fert 1 -1 variety*fert 1 -1 0 0 0 0;
  estimate 'Fert 1 - Fert 2 for Variety 2' fert 1 -1 variety*fert 0 0 1 -1 0 0;
  estimate 'Fert 1 - Fert 2 for Variety 3' fert 1 -1 variety*fert 0 0 0 0 1 -1;
run;