THE SOIL AS A FACTOR 21 



Cultivation. In the open, cultivation has for its object the prep- 

 aration of the seed bed, liberation of plant food, and the destruc- 

 tion of weeds. These results are secured chiefly through spading, 

 plowing, harrowing, hoeing, and cultivation. Under greenhouse 

 conditions, however, these mechanical operations cannot be carried 

 on as they are in the open field, and the wise gardener, whether 

 working under outdoor or greenhouse conditions, cultivates his 

 crop well before he plants it. In fact, many persons believe that a 

 very large part of the cultivation of a crop can be done before the 

 crop is planted. This is emphatically true with greenhouse crops. 

 The important part of the cultivation of greenhouse crops takes 

 place in the compost heap. The work of fining the soil and of 

 liberating plant food is almost entirely accomplished while the soil 

 is in the compost heap, as is also to a less extent the destruction 

 of weeds. In a properly constructed compost heap the successive 

 workings to which the soil is subjected fine the particles by grind- 

 ing them together and thoroughly mix the several component 

 parts of the heap. This mixing and grinding process also has a 

 tendency to render the plant food which is contained in the soil 

 more available, so that two of the important objects of cultivation 

 are readily accomplished in the compost heap. If the handling of 

 the soil is at sufficiently frequent intervals and the heap is not too 

 deep, a considerable percentage of the weed seeds which are con- 

 tained in it may be induced to germinate and the young weeds 

 killed by the handling of the soil. 



The compost heap. The construction of the compost heap and 

 its care are, therefore, most vital matters to gardeners cultivating 

 under glass. Composts are necessary in gardening under glass be- 

 cause maximum production is required of special plants. Natural 

 soils are not developed for this purpose but rather for an average 

 production from a large variety of plants. It is necessary, there- 

 fore, in order to secure maximum production with any plant to 

 prepare a soil for this special purpose. Two types of compost 

 must be considered : first, special composts for a particular pur- 

 pose in order to obtain plant food of the desired kind and in 

 necessary proportions ; and second, a general compost for use as 

 a basis for special crops or composts. The general compost heap 

 should consist of foundation or base material ; that is, it should 



