The Effects of Light Intensity,Day Temperature and Water Supply on the Fruit-Ripening Disorders and Yield of two Varieties of Tomato

A study was made of the effects on fruit-ripening disorders and crop yield of shaded and unshaded glasshouses maintained at both high and low daytime temperatures (80° F. (26 ? 5° C.) and 65° F. (18 ? 3° C.)), in which were grown two varieties of tomatoes (Potentate and Ware Cross) at two levels of watering.

Shading the glasshouses reduced the proportion of non-uniformly coloured fruit at the high temperature. At the low temperature, shading reduced the proportion in i960 but there was no effect in 1959. Light watering reduced the proportion of non-uniformly coloured fruit in the first year but it had little effect in the second year. The variety Ware Cross bore approximately 10% fewer non-uniformly coloured fruit than did Potentate in both years.

Shading the glasshouses reduced yield in both years, the decrease being greater (62%) in the very dull year of i960 than it was (40%) in the very sunny year of 1959. The house at the low day temperature yielded a 30% greater weight of crop than the warmer house. In both years the heavily watered plants yielded more than the lightly watered plants because of an increase in mean fruit size. Potentate and Ware Cross yielded similar weights of crop in both years but Ware Cross bore more fruits and had a smaller mean fruit size.

The gross cash return obtained in 1960 was reduced by shading the glasshouses, by maintaining a high day temperature and by growing the variety Potentate as opposed to Ware Cross. The differences in the watering regimes employed had little effect on the cash return obtained.

By assuming that yield and quality have simple mathematical relations with degree of shading, the profitability of shading is discussed. It is shown that shading is not likely to be profitable.