MANURES, LIME AND FERTILIZERS 65 
management than in out-of-door cropping. The func- 
tions of lime are varied and may be cnumerated as 
follows: (1) It is an important food clement of plants, 
although all soils probably contain sufficient lime to mect 
the needs of greenhouse vegetable crops, so that it is not 
considered a normal fertilizer, such as nitrogen, phos- 
phorus and potassium. (2) It maintains a neutral or 
alkaline soil solution which is essential to the most satis- 
factory growth of some crops, especially the clovers. 
(3) It is favorable to the micro-organisms of the soil 
which are so important in relation to the supply of avail- 
able nitrogen. (4) It helps to maintain satisfactory sani- 
tary soil conditions; that is, it promotes the work of 
friendly bacteria and retards the action of injurious forms, 
and of certain disease germs which are harmful to forcing 
crops. In the management of greenhouse soils it prob- 
ably pays to use lime for its beneficial sanitary effects, 
were there no other considerations. (5) It liberates plant 
food, including both of the important mineral constitu- 
ents—phosphoric acid and potash—although this function 
may not be of great consequence in heavily manured 
greenhouse soils. (6) It is destructive to toxic substances 
in the soil, and this function may be of great importance 
in greenhouse management where there is little oppor- 
tunity for long-time rotations. (7) It aids in the breaking 
down of insoluble compounds and in making them avail- 
able to plants. (8) It forms a base for fixing and retain- 
ing humus. (9) It flocculates the finest particles of silt 
and clay soils into granular masses, thus materially im- 
proving the physical structure of such soils. After treat- 
ment with lime, these soils are more open and porous, 
better aerated, more easily penetrated by plant roots; 
they dry quicker at the surface and possess better 
physical properties in every respect for the forcing of 
vegetables. All heavy soils used in vegetable forcing 
should receive frequent and liberal applications of lime. 
