THE EFFECT OF CULTIVAR, METHOD OF PLANTING AND PLANT POPULATION ON THE YIELD AND QUALITY OF SMALL POTATO TUBERS GROWN FOR EXPORT UNDER TROPICAL CONDITIONS IN THE SUDAN
Investigations which included an experimental programme on cultural practices such as plant population, planting-methods and irrigation were undertaken in order to evaluate the performance of potentially suitable potato cultivars.
Claypool and Morris (1932) studied the effect of spacing on yield and tuber size of the potato cultivar 'Netted Gem', planted on hills with rows 32 inches apart and 6, 12, 18 and 24 inches between tubers in the rows. The highest total yields and yields of U.S. No. 1 tubers were obtained from a spacing of six inches between plants. Total yields gradually decreased as the planting distances increased, but not in proportion to the change in planting distance.
Plants spaced at 18 or 24 inches apart produced larger tubers than the plants at a 6 or 12-inch spacing. Tubers planted at a wide spacing were rough and inclined to have hollow centres, whereas tubers grown at a spacing of 6 and 12 inches were of a medium size, smooth and free from cavities.
A consistent increase in the number of tubers produced per hill was found as the plants were spaced farther apart; tuber size also increased as the planting distances became greater.
White-Stevens and Wessels (1939) showed that wide spacing of 15 inches between plants in the row, with rows spaced 33 inches apart were best at low fertilizer applications, whereas a close spacing of 11 inches gave the highest yields with fertilizer (5–10–5) applied at 2000 pounds per acre. Irrigation was most effective when plants were widely spaced. The maximum response from irrigation was obtained with fertilizer applications of 2000 pounds per acre at a seed spacing of 11 inches.
No interactions were found between seed spacing, irrigation and seasons or between fertilizer, irrigation and season. The authors also concluded that rainfall at the time of emergence of the sprouts, during periods of major shoot growth and at the onset of tuber enlargement was directly correlated with yield. Irrigation also increased yield in dry seasons.