The effect of different pre-planting treatments on subsequent growth and yield of Rua potatoes

Abstract

Because some growers, especially seed growers, have experienced difficulty producing a high yield of Rua potatoes, the effect of some pre-planting treatments on subsequent growth and yield were investigated. Tubers were either sprouted over two or six weeks, cut longitudinally, dipped in gibberellic acid (GA) or exposed on alternate days to hot and cold temperatures and then planted on the same day in a randomised block.

Rate, evenness and final emergence were recorded. On four harvests at approximately monthly intervals weight and number of tubers produced, and their specific gravity were recorded. At the first two harvests the fresh weight of haulms, stem internode length and number of stems were also measured. Sprouted tubers emerged more evenly and rapidly than non sprouted tubers, while exposing tubers on alternate days to hot and cold temperatures resulted in some physiological breakdown and less than half emerged. Plants from long sprouted and GA dipped tubers produced more stems per plant than the non sprouted treatments, with the short sprouted treatment intermediate.

At each harvest the long sprouted treatment produced the highest yields followed by the short sprouted treatment. The non-sprouted and out tubers were third in yield while the GA treatment averaged only half the yield of the long sprouted treatment. The superior yield of the long sprouted treatment, double that of the non sprouted treatments at the first harvest, was still evident, although less so, at the final harvest. The total number of tubers produced was significantly greater from the GA treatment.

Three practices of potential value for growing Rua potatoes have arisen from this work. These include the use of GA to increase the proportion of small tubers in seed potato crops, chitting tubers to increase yields of table potatoes and the use of cut table potatoes as a cheaper source of planting material.