Abstract
The purpose of this investigation is to examine the effect of crude ettringite (CET) on the growth and the nitrogen fixation of ladino clover, red clover and alfalfa. CET was synthesized from blastfurnace slag and gypsum produced in the process of desulfurization at electric power station, and it contained about 60% of ettringite and some other compounds. In this experiment, leguminous forages were sown in 1/2000 are wagner pot containing 15kg of acidic mineral soil of which pH was adjusted at 5.5, 6.5 and 7.5 with CET or calcium hydroxide. The culture was carried out in a non-heating glasshouse from Sept. 12, 1977 to May 10, 1978. The cutting of plant top was made three times (Jan. 21, Apr. 15 and May 10, 1978) and the growth of forages were compared with one another. Besides, potassium uptake and nitrogen fixing capacity by leguminous forages were measured. The results obtained were as follows. 1. The neutralizing capacity of CET was less than that of calcium hydroxide, while the values of initial soil pH adjusted by CET were almost constantly maintained through the experimental period. 2. The growth of leguminous forages was remarkably affected by soil pH and was considerably improved by the application of CET compared with that of calcium hydroxide. The species were ranked as follows according to the effectiveness of CET: alfalfa>red clover>ladino clover. Moreover, its effectiveness seemed to be enhanced with proceeding of cutting. 3. Although the potassiun uptake by leguminous forages increased with the application of CET, it was not recognized in this experiment that the effect of CET on the growth was due to the increase of potassium uptake by the leguminous forages. 4. The application of CET resulted in the increase of nitrogen fixing capacity per plant by improving the nodule formation and nitrogen fixing capacity per unit weight of nodules. 5. It was assumed from this investigation that CET is much more beneficial material for neutralizing soil acidity than calcium hydroxide in the cultivation of leguminous forages.
