Tuberization and effect of age of seedlings at transplant on yield of seed-propagated cassava

Abstract

Two experiments were carried out firstly to study the processes of development and tuber initiation in cassava seedlings, and secondly, to determine the appropriate age at which cassava seedlings should be transplanted to ensure optimum field establishment and higher yield. In the first experiment, nursed seedlings were uprooted at weekly intervals from time of emergence for 9 weeks, and observed for root and shoot development. Transverse sections of roots were examined for the presence of starch grains. In the second experiment, seedlings at 27, 34, 41 and 48 days old were transplanted (naked root) to the field and observed for survival and tuber yield after 10 months of growth. Most seeds germinated within 7-16 days after sowing but a few germinated after 70 days. During the first 9 weeks of seedling growth, an average of three leaves unfolded every week on the main stem. Stem elongation occurred at a fairly constant rate of 5.1 mm /day while tap root elongation was 8.6 mm/day for the first week, and 2.4 mm/day over the next 6 weeks. Lateral root elongation was high, averaging about 9.3 mm/day over the first 6 weeks of growth. Starch grains were first observed in the tap root at 4 weeks and in the lateral root tissues at 5 weeks. Proliferation of starch-filled cortical cells began in the tap and lateral roots at 5 and 9 weeks respectively. Percentage survival were 28, 63, 80, and 67 for seedlings transplanted at 27, 34, 41 and 48 days old respectively. Tuber yield ranged from 6525 kg/ha for the 27 days old seedlings to 17 764 kg/ha for the 41 days old seedlings. It was concluded that the most appropriate age at which to transplant cassava seedlings to ensure optimum survival and yield was 41 days after sowing.


(Ghana Journal of Agricultural Science, 1997, 30(1): 9-14)