AVAILABILITY OF REPLACEABLE CALCIUM FROM DIFFERENT TYPES OF COLLOIDS AS AFFECTED BY DEGREE OF CALCIUM SATURATION

Abstract

The availability to soybean seedlings and the replaceability by equivalent amounts of HC1 and BaCl2 of the replaceable Ca of 5 different colloids was studied. The colloids included peat, kaolinite, illite, Wyoming bentonite, and Mississippi bentonite, each of which was investigated at 3 degrees of Ca saturation (40, 60, and 80%). The plant availability measurements were made by growing soybean seedlings on cultures made up of the CaH colloids and quartz sand. 0.2 ME of replaceable Ca was offered per plant. The order of availability of Ca to the soybean seedlings was peat > kaolinite > Wyoming bentonite and illite > Mississippi bentonite. Plant availability increased with increases in % Ca saturation in all colloids. There was a close relationship between the amt. of Ca taken up by the soybean plants and the amt. replaced by an equivalent quantity of HC1.