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The effect of photoperiod and soil nutrient level of nitrogen, phosphorous and potassium on the compostion and growth of the tomato Gubbels, Cleophas Peter

Abstract

Tomatoes were grown in a greenhouse during the winter with different levels of nitrogen, phosphorous and potassium fertilizer under both normal day length and normal day length extended with artificial light. Growth rates of plants and yields of fruit were recorded. An analysis was carried out on the fruit for sugars, titratable acidity and ascorbic acid and in both the leaves and the fruit, dry weight, total ash, total nitrogen, phosphorous and calcium were determined. Additional illumination depressed yield and fruit size but hastened maturity of the fruit by more than three weeks. In general, additional light increased ascorbic acid and titrateable acidity in the fruit, decreased moisture in the leaves, increased moisture in the fruit, increased ash weight and potassium in the leaves and fruit and increased calcium content of the leaves. Irradiation also increased the sugar content of the fruit where low levels of soil nitrogen were used but decreased sugar content of the fruit where higher levels of nitrogen were used. Low nitrogen in the soil was associated with high ash content of the leaves and fruit, especially under irradiation. Nitrogen increases in the soil resulted in increased nitrogen and decreased phosphorous and potassium content of the leaves and fruit and in increased calcium content of the leaves. The higher soil levels of phosphorous and potash tended to increase the ascorbic acid and titratable acidity content of the fruit, increase the phosphorous and potassium content of the leaves and fruit and decrease the calcium content of the leaves. Yield was increased as a result of the higher nitrogen treatments under normal light only. The fertilizer applications used had no effect in increasing yield under supplemental illumination.

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