The potato (Solanum tuberosum L.) crop serves as a staple food worldwide and is capable of
reducing the world’s food shortages because unlike cereals and other agricultural crops, it is less
affected by prices in the international markets. Research on alleviation of food crises suggested
root and tuber crops such as potatoes to be the solution to the problem of food shortage. The crop
is widely cultivated but is difficult to produce due to susceptibility to numerous pests and
pathogenic organisms, as well as abiotic stresses. To control these pests and diseases, strategies
to limit susceptibility to factors that interfere with the growth and development of plants, or
breeding new varieties that are able to withstand stresses are being researched. Recent studies
have shown that non essential nutrients such as Silicon (Si) are beneficial to plants in terms of
yield, protection from fungal diseases and improved uptake of phosphorus.
Since very little research has focused on the role of Si in improving potato production, three
glasshouse pot trials were conducted at the Hatfield Experimental farm and Department of Plant
Pathology glasshouses of the University of Pretoria to evaluate the effect of various soil
amendments on potato yield and quality. The effect of these soil amendments on pH was also
investigated as P-uptake and development of common scab in potatoes are pH dependent. The
soil amendments consisted of different silicon sources and an agricultural lime. The Si sources
were Calmasil slag (Middleburg) (30% Si- containing liming material), fly ash (50% Si nonliming
material), and Si fume/ash (99% Si non-liming material). Agricultural lime (CaCO3) was
included as a control.
The purpose of the first two trials was to identify the most promising silicon-containing source
for potato production, while the third trial evaluated the effect of this silicon source on soil pH
and potato tuber yield. In all three trials, agricultural lime was used as a control. Due to the high
demand for nutrients by the potato crop, other nutrient elements were added to the soil through
fertigation every 7 to 14 days, depending on the growth stage of the plants. Plants were irrigated
with distilled water when necessary to maintain an adequate moisture level i.e. moist but not too
wet. Weekly observations on growth parameters were made. To select the most promising soil
amendment, parameters such as leaf chlorophyll content, plant height, tuber number and mass
(Fwt), fresh and dry weight (top growth) and change in soil pH were analyzed. Slag treated
plants tended to produce tubers with higher mass and better appearance. In this study the highest
increase in soil pH was observed in soil mixed with slag, compared to all the other silicon
sources. Although there was no significant difference observed among treatments there was a
distinct difference in plant growth between trials when soil was amended with lime and slag.
Plants treated with slag tended to produce tubers that weigh more, whilst plants treated with lime grew taller and had the highest tuber number. There was a significant rise in soil pH from both
lime and slag, which might have in turn influenced vegetative and tuber growth.
Dissertation (MInst(Agrar)--University of Pretoria, 2014.