The effect of seedling age and pricking-out of true potato (Solanum tuberosum l.) seed seedlings on plant survival and tuber yield
The effect of transplanting true potato (Solanum tuberosum) seedlings of hybrid and open pollinated progenies, either pricked-out or not at various ages (28, 35 and 42 days after sowing - DAS) on plant survival and tuber yield was investigated under field conditions at Kabete Field Station. University of Nairobi, during the shan and long rains of 1994/95 cropping seasons. A factorial experiment arranged in Randomized Complete Block Design with three replications was used. Data collected included number of true leaves of seedlings, seedling height and seedling vigour at transplanting, plant survival at establishment and at maturity, plant vigour in the field, top fresh and dry weights per hill. total and marketable tuber yield, mean tuber yield per plant and tuber size distribution. The general performance of seedling age treatment indicated a significant effect during the long rains. The oldest seedlings (42 days) had more plants surviving (80.9 and 72.9% at establishment and maturity, respectively) and more total (18.5 t/ha) and marketable (15.6 t/ha) tuber yields than the young ones. Pricking-out increased plant survival rate at maturity from 74.7 to 80.2 % (shan rains), 53.8 to 63.1 % (long rains). total tuber yield from 28.2 to 34.4 and 13.2 to 15.7 t/ha (shan and long rains. respectively) and marketable tuber yield from 25.1 to 30.6 t/ha during the shan rains. Hybrid progeny was significantly superior to open-pollinated progeny in plant survival (66.2 %) at maturity during the long rains, total (34.3 and 18.0 t/ha) and marketable (31.2 and 14.5 tlha) tuber yields in shan and long rains, respectively. The interaction between seedling age and pricking-our was not significant for most of variables except for seedling vigour and height at transplanting. Pricking-our effect increased with an increase in seedling age for seedling height and decreased with an increase in seedling age for seedling vigour .