The Effects of Nitrogen,Phosphorus, Potassium,Magnesium and Lime in Factorial Combination on the Size and Shape of Glasshouse Tomatoes

The effects of nutrition on tomato fruit size and shape are summarized, based on the results of a factorial trial in heated glasshouse borders. The varieties grown were Potentate, J168 and Moneymaker.

The average weight per fruit, calculated from total weights and numbers, was decreased by potassium and magnesium sulphates. Both high nitrogen (760–830 lb. N per acre) and low nitrogen (30–150 lb. N) decreased the weight per fruit as compared with the intermediate nitrogen level (300–380 lb. N). The weight per fruit of varieties J168 and Moneymaker, grown for two seasons, was decreased significantly by high phosphorus in one year and increased by lime in both years.

The uniformly coloured and regularly shaped fruits were graded into four commercial-size categories. Expressed as percentages of the sum of these four grades, the proportion of large fruits showed nutritional responses generally similar to those for average weight per fruit, with opposing trends in the smaller size categories.

The proportion of somewhat irregularly shaped fruit in the uniformly coloured categories, studied for six seasons, was appreciably affected by nutrition. Fruit shape was improved by high potassium and magnesium, and also by nitrogen deficiency. High phosphorus affected the shape adversely. Liming improved the shape of fruit of variety Potentate in three out of four seasons, but the opposite effect was found with J168 and Moneymaker in the final season.

The relation of fruit size and shape to soil salinity is discussed.