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C ONSIDERABLE work has been done in investigating the causes of boron starvation in plants in many areas of the United States. Several theories have been proposed and valuable information has been reported concerning the causes of boron starvation in plants.Naftel (8) 3 studied the injurious effect of overliming and was the first to report this to be directly related to boron. He suggested that overliming might increase the growth of micro-organisms, which :in turn would compete with the plants for the available boron of the soil.Cook and Millar (1) found that beets growing on soils high in active calcium were much more likely to be boron deficient than if the active calcium were low, and [they stated that factors of great importance affecting the boron supply were calcium, organic matter, and soil texture.Midgley and Dunklee ( 6) found that as high as 90% of the boron added was fixed when a podzol At horizon and Maine peat moss were overlimed; but they reported that boron added to limestone was not fixed, since both calcium and magnesium borates are relatively soluble.Powers (9) showed, with greenhouse pot experiments on Oregon soils, that where lime was used, boron in some cases was less effective, and that where sulfur was used, the boron availability was somewhat improved. When high levels of calcium were used in growing oranges in sand cultures, Haas (3) found it necessary to add larger amounts of boron to prevent boron starvation.Cook and Millar (1) reported calcium and magnesium carbonates to be effective in masking crop injury caused by excessive applications of boron; however, calcium and magnesium sulfates were only partially effective in fixing boron in forms not available to soybeans.Ferguson and Wright (2) studied the effects of sodium and calcium borates in the nutrient solution on limed and unlimed sands. They · found that boron starvation symptoms were common where the plants received calcium borate, and thereby concluded that boron deficiency troubles may be greater where calcium borate instead of sodium borate is used as the source of available boron. EXPERIMENTAL PROCEDURE AND RESULTS BORON FIXATION BY CLAY AND HUMUS AT VARIOUS PH LEVELSOne theory of overliming was that the soil fixed the boron at higher pH levels resulting from the heavy application of lime. It seemed