The influence of physiological age, stem numbers and fertility on yield and grade of Russet Burbank potatoes

The present study was initiated to determine if increased stem numbers produced by physiologically older seed can be compensated for by increased fertilizer rate. Seed tubers held for 2 months at 16 C (physiological older seed) which averaged 3.7 main stems were compared in yield parameters to physiologically younger seed kept at 4 C (average 2.4 stems). The comparison was made at three levels of fertilizer 0, 140, and 280 kg/ha of nitrogen applied in a 16:16:16 (N-P2O5-K2O) formulation. Seed size and spacing were equal. Total and U.S. No. 1 yield were significantly higher for the younger seed. The greatest difference was that the younger seed at 140 kg/ha fertilizer yielded significantly more large size (over 280 g size) tubers than the older seed at equal to or double (280 kg/ha) the fertilizer rate indicating that additional fertilizer was not sufficient to overcome the effects of higher stem numbers from older seed. On the other hand, the older seed produced significantly higher yield of the undesirable small sizes.