THE EFFECT OF NITROGEN AND POTASSIUM ON TOMATO QUALITY

The effect on quality of 3 levels of nitrogen (225, 450 and 675 kg/ha N) and 3 levels of potassium (200, 400 and 600 kg/ha K) in factorial combination were measured over a period of 3 years. The percentage of Class 1 round fruit increased significantly as the application of potassium increased but, except for the first year, decreased with increasing nitrogen application. Three higher rates of application of approximately equal amounts of nitrogen and potassium applied in the first 2 years of the experiments further significantly increased the percentage Class 1 round fruit.

Subsequently, because of decreasing soil K levels, potassium applications were increased to 600, 1200 and 1800 kg/ha K in factorial combination with 225, 450 and 675 kg/ha N. The 3 higher rates of application of potassium 1800, 2400 and 3200 kg/ha K were applied at a constant 900 kg/ha N. Except for the final year quality improved up to the highest rate of application of potassium.

Gypsum, applied once only at a rate of 12 tonne per hectare for chrysanthemum trials four years previous to the first tomato crop, increased the percentage Class 1 round fruit in the total ripe yield at low, but not high rates of application of nitrogen and potassium for the first 3 crops. There were no further significant effects from 1969 onwards when part of the potassium treatments were applied as base dressings of sulphate of potash.

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