38 RELATION OF LIME AND MAGNESIA TO PLANT GROWTH. 
of phosphoric acid, as already pointed out. It is not the province of 
this report to discuss at any length the physiological action of lime 
and magnesia. That subject is presented in detail in the first part of 
this bulletin, in which Dr. Loew, from the results of investigations, 
draws the conclusion that where magnesia is in excess, the lime, as the 
stronger base, will combine with the acid of the magnesium salt, while 
the magnesia will enter into the place which the lime had occupied in 
the organized structure. Again, if lime salts are in great excess the 
formation of magnesium phosphate, and consequently the assimilation 
of phosphoric acid will be retarded. 
An excess of magnesia in soils may exert a poisonous action upon 
plants. This has been noticed in applying limestone containing a 
large percentage of magnesia. Again, the continued application of 
potassic fertilizers as kainit and carnallit containing magnesia has in 
some instances rendered the soil unfit for agricultural purposes. This 
is probably due to the raising of the magnesia content of the soil, as 
may be done by continued application of certain crude potash salts. 
A sample examined by the writer contained 9.37 per cent of magnesia. 
The difference in the lime and magnesia content may also be influ- 
enced in another way. Goessman reports’ an increased loss of lime 
from soils to which muriate of potash was applied. The analysis of 
drainage water from such plats showed a large percentage of calcium 
chlorid. 
Magnesia is found naturally in alkali soils of the arid districts and 
possibly in soils of the humid regions to such an extent as to render 
them barren of any vegetation. It is also highly probable that the 
magnesia content of a great many soils is excessive to such an extent 
as to hinder them in producing maximum crops. 
THE OBJECT OF THE EXPERIMENTS. 
The object of the work herein reported was to study the effect of 
varying amounts of calcium and magnesium salts on the growth of 
economic plants, and especially the ameliorating effects of lime salts 
in overcoming the noxious results of an excess of magnesia. It was 
also sought to determine the ratio between the two bases which best 
promote the early germination and quick development of plants. 
This might throw some light on the question of liming, as giving some 
indication of the amount of lime to be supplied, and in other cases 
pointing out the danger of adding an excessive amount of magnesia 
through applying certain limestone and potassic fertilizers containing 
that base. Another point sought to be brought out is the form in 
which lime best acts in counteracting the noxious effects of an excess 
of magnesia and also the testing of chemical nutrients other than lime 
in ameliorating such evil results. 
The experiments described were begun in 1899, and cultures of the 
1Mass. Hatch. Exp. Sta. Bulletin No. 38. 
