MANURES, LIME AND FERTILIZERS 65 



management than in out-of-door cropping. The func- 

 tions of lime arc varied and may be enumerated -as 

 follows: (1) It is an important food clement of plants, 

 although all soils probably contain sufficient lime to meet 

 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. 



