22 GARDEN FARMING 



be made from the heaviest soil to be used in any greenhouse 

 operation, which should carry a maximum amount of fiber, and it 

 should also have a liberal supply of humus, preferably of a rather 

 heavy nature, such as that from peat, muck, or cow manure, or for 

 special purposes, from cow manure alone. It is much easier to 

 lighten soil than to render it heavy after it has been thoroughly 

 composted. Lightening can be accomplished by the admixture of 

 sand, leaf mold, or peat ; sometimes coconut fiber and materials 

 of this sort are also used for the purpose, but for making a soil 

 heavy, clay alone must be used. Since clay cannot be handled in 

 the same way as the lighter materials, it is best to construct the 

 compost heap of the heaviest loams that will be required for any 

 crop to be grown and depend upon the use of sand, leaf mold, etc. 

 for making those special types of soil required by particular crops. 

 Time of preparation. The compost heap should be prepared 

 several months before it is needed, in order to allow sufficient 

 time for the accomplishment of important changes which take 

 place in the soil. The reason for this is that all plant foods are 

 more or less inert, and in order to make them available for use by 

 plants certain low forms of life must have opportunity to act upon 

 them, and certain mechanical as well as chemical changes must 

 take place through decomposition and fermentation ; in other 

 words, the soil must have time to digest these raw materials be- 

 fore the plant can feed upon them. Certain factors, such as heat, 

 moisture, the presence of lime, and an abundance of decaying 

 organic matter, are desirable in order that a compost of the best 

 character may be produced. As a guide to the preparation of plant 

 foods the chemist determines the kinds and sources of foods re- 

 quired by various plants. This we supply as best we can from 

 manures, fertilizers, etc., but these materials are raw and crude, 

 and in order to prepare the most important of them for use by 

 the plants we must have the beneficial effect of the soil bacteria. 

 These organisms are too minute to be observed except with the 

 aid of the highest-power compound microscope, yet they are of 

 the greatest economic importance to farmers and gardeners alike. 

 Their function is to transform this inactive plant food of the rock 

 particles, decaying vegetation, and animal remains into active plant 

 food ; and in order that these helpmates may do their best work 



