Technological Quality of Potato Tubers: Effect of Potassium Fertilization and Application Time

Abstract

The effect of potassium fertilization and time of application on yield and tuber quality of potato (Solanum tuberosum L., cv. Agria) was studied in Bekaa region in Lebanon. Potassium was applied in one split at tuber initiation (T1) and at tuber bulking (T2) in four different rates: K0 (0 kg/ha), K1 (100 kg/ha), K2 (200 kg/ha) and K3 (300 kg/ha). Results showed that aerial dry matter decreased and tuber dry matter increased during the growing period. The dry matter accumulation was dependent on potassium fertilization. Potassium concentration gradually decreased in leaves and increased in tubers during the growing period, while the most potassium treatment (K3) has accumulated at harvest, higher potassium concentrations in leaves and tubers, with more emphasis to application time T2 with respect to T1. Moreover, potassium has accelerated significantly (p<0.05) tuber dry matter accumulation. This was revealed by growth rate and harvest index values that were significantly higher (p<0.05) in K3 treatment with comparison to other treatments. Results also showed that fresh tuber yields increased with potassium fertilization and were more pronounced with T2 application whereas K3 had significantly (p<0.05) the highest value of 62.9 t/ha (K3). Yield augmentation was primarily due to an increase in tuber size in the larger (> 60 mm) and the medium (35 – 60 mm) grades. In addition, results showed that tuber dry matter content and specific gravity were statistically dependent on potassium fertilization and application time (p<0.05). The highest potassium treatment K3, regardless of application time, gave the best tuber quality of industrial potato by having the highest dry matter and the lowest reducing sugar contents. Finally, the results of this study suggest that maximum potato yield was obtained with K3 treatment (300 kg/ ha) applied during tuber bulking stage (T2).