Il. EXPERIMENTAL STUDY OF THE RELATION OF LIME AND 
MAGNESIA TO PLANT GROWTH. 
By D. W. May, 
Of the Office of Experiment Stations. 
INTRODUCTION. 
The wide distribution of lime and magnesia in soils is very evident 
from the tables of analyses presented in the first part of this bulletin. 
The fact that these elements are in some degree present in all soils and 
able to supply the direct needs of plants has probably been the reason 
for the neglect of the extended study of their relations to each other. 
THE ROLE OF LIME IN THE SOIL. 
The necessity of lime and magnesia in plant production is a fact that 
has long been recognized. The favorable influence of lime on certain 
soils has led to the very common agricultural practice of liming. The 
presence of lime may serve several purposes. It supplies this neces- 
sary element in the construction of plant tissue, hastens the decompo- 
sition of organic matter, facilitates the assimilation of other elements, 
and produces favorable physical conditions in the soil. It also causes 
an increased bacteriological and fungous growth in the soil, in some 
cases favorable to plants, as in reducing the club-root of the turnip 
and cabbage,’ and sometimes unfavorable, as increasing the scab of 
potatoes.” Deherain mentions that agriculture in some sections of 
France has by the use of lime undergone an entire revolution. 
Lime may then serve in plant production in several réles, which 
may be denominated physical, chemical, and physiological. Physically, 
it may be of benefit when added to stiff, retentive clays, rendering 
them mellow, better drained, and more easily cultivated. Chemically, 
it will render available and within the ability of the plant to absorb 
certain necessary elements locked up in an insoluble combination. 
Physiologically, it has a necessary réle to play in carrying on the 
functions of plant growth and the building up of cells. It is the latter 
role of the element in connection with magnesia that this paper deals. 
THE ROLE OF MAGNESIA IN THE SOIL. 
Certain experiments as well as the percentage of magnesia found in 
plants, especially in the seeds, prove the necessity of this element in 
plant production. Besides being a necessary constituent of plants, it 
plays a physiological réle, serving especially in aiding the assimilation 
1Campbell, Board Agr. Rpt., Great Britain, 1894-95. 
? Wheeler, Rhode Island Rpt., 1896. 
