growth method
1 = a
2 = b
3 = c

method and variety crossed
1 = method 1 variety 1
2 = method 1 variety 2
3 = method 1 variety 3
4 = method 1 variety 4
5 = method 1 variety 6
6 = method 2 variety 1
7 = method 2 variety 2
8 = method 2 variety 3
9 = method 2 variety 4
10 = method 2 variety 5
11 = method 3 variety 1
12 = method 3 variety 2
13 = method 3 variety 3
14 = method 3 variety 4
15 = method 3 variety 5