|Abstract or Summary
- This paper records a series of experiments conducted furing a one-year period to determine the effects of boron upon the growth and fruiting of Marshall and Corvallis strawberries, two of the leading commercial varieties in Oregon. The problem was approached in four ways: (1) applications of dry borax and borax in solution to field plantings; (2) applications of borax in solution to plants growing in No. 10 cans containing soil; (3) growing Corvallis plants in sand cultures receiving nutrient solutions containing varying amounts of borax; and (4) growing Corvallis plants in water cultures containing varying amounts of borax. Because of the limited time available for the study and because of the growth habits of the crop, no conclusions were drawn as to the effect of boron on fruiting. Yields were very inconsistent from the field plots treated with borax in the spring. In the greenhouse, the unnatural growing conditions during the winter, combined with poor pollination and irregular fruiting, eliminated yield data from plants growing in soil, sand cultures, and water cultures. Growth and fruiting from all water culture plants was poor except from three plants which made excellent growth in a colloidal nutrient solution. However, normal berries natured and ripened from some plants in cans of soil and from some plants in the sand culture experiments that remained alive until the end of the experiment. Concentrations of borax as high as 200 pounds per acre (in cans of soil) had no visible effect on external characteristics of the berries. Chemical analyses of berries from some of the treatments showed that a slight increase in boron content of the berries accompanied the increase in borax added to the soil. However, in the highest treatment, an increase of 2,000 per cent in the borax added to the soil resulted in an increase of only 38 per cent in the boron content of the berries. In contrast to the limited intake of boron by the berries was the marked absorption of boron by the leaves from the same treatments. For example, leaves from plants treated with 50 pounds of borax per acre contained 84 p.p.m. boron, whereas those from non-treated plants contained 44 p.p.m. Leaves from the plants receiving greater amounts of borax showed still higher boron content. This fact may offer a "lead" involving the use of leaf analysis to determine the boron requirements of strawberries. This possibility is not presented as a new idea, for the possible use of leaf analysis in determining the boron needs of other crops has been mentioned in the literature. However, leaf analysis for boron may also be applicable to strawberries. Associated with the increase of boron in the leaves from the plants treated with borax was a correlation between the reddish-brown marginal discoloration of leaves and the boron content of the discolored leaves. In the samples analyzed, the boron content of marginally-discolored leaves was consistently higher than that of normally-colored leaves. These discolorations were attributed to boron toxicity. Descriptions and photographs are presented in establishing the toxicity, but it is not concluded that marginal discoloration alone can be used for the determination of boron toxicity of strawberries. Too many other factors may also cause marginal discoloration of a similar nature. However, it is suggested that leaf discoloration might be substantiated by chemical analysis to prove that toxic concentrations of boron were being absorbed by the leaves.