The aim of this thesis was to find the best possible planting distance and haulm killing timing for seed potato production. Thesis was carried out as field trial and it was built in Tyrnävä, Härmä farm in the summer 2013.

The goal was to find best the solution to get the best financial result per hectare. The affecting factors are costs of seed, yield and tuber size distribution.

There were three planting distances: 17 cm, 24 cm and 31 cm. Haulm killing times were also three: early, middle early and late. The total number of subplots was 27. Trial was made in cooperation with HZPC Kantaperuna.

Results in this trial were quite clear. Planting distances and haulm killing times have a clear impact of the yield. The best financial result was 17 cm planting distance and late haulm killing. The lowest financial result was the widest planting distance and early haulm killing. Difference between the best and the worst results was 3000 euros per hectare.