Effect of Planting Method on Growth, Yield and Quality of Three Irish Potato (Solanum tuberosum) Varieties Grown in Zimbabwe

The planting methods currently used by Irish potato farmers were optimized for old varieties more than three decades ago. No such work has since been done regardless of the newer varieties that have been introduced since then. Hence, an experiment was conducted to investigate the effect of two planting methods (planting in the furrow; ridging up to a height of 20 cm immediately after planting (IAP)) on three varieties of Irish potato (BP1, Mnandi and KY20) that are grown in Zimbabwe. The trial was done at Africa University Farm in Mutare, Zimbabwe. The experiment was a 2 x 3 factorial arrangement laid out in 4 replications using a randomized complete block design. The first factor was the two planting methods and the second factor was the three varieties. The unit plot size was 3.6 x 3.6 m2 and the net harvestable plot was 2 m x 2 m discarding the border rows. The inter and intra-row spacings were 90 and 30 cm, respectively. The result showed that ridging delayed crop emergence as compared to furrow planting (43.4% vs. 35.7% 8 days after planting and 92.7% vs. 78.4% 12 days after planting (DAP) but did not significantly reduce crop yield, which, in fact, it increased. Ridge planting reduced the incidence of green tubers by close to 50%. Stem density per plant was influenced by variation in variety. Marketable tuber yield was improved by ridge planting. Specific gravity decreased with ridge planting but quality of potato did not deteriorate. This study showed that ridging IAP was beneficial for the varieties used but more work is needed to establish the ideal tuber seed piece size as the ability of tubers to emerge might be dependent on the size of the tuber seed piece planted.