22 THE FIRST BOOK OF FARMING 



etc. Put cuttings of same plants into tumblers filled 

 with clay that has been wet and stirred very thor- 

 oughly, until it is about the consistency of cake bat- 

 ter. Keep the sand and puddled clay moist ; do not 

 allow .the clay to crack, which it will do if it dries. 

 The cuttings in the sand will strike root and grow, 

 while most, if not all, those in the clay will soon die. 

 The reason for this is that the sand is well ventilated 

 and there is sufficient air for root development, while 

 the clay is very poorly ventilated, and there is not 

 sufficient air for root growth. 



These experiments show us that to develop and do 

 their work roots need air or a well-ventilated soil. 



We have found the conditions which are necessary 

 for the growth and development of plant roots, 

 namely : 



A firm, mellow soil. 



A moist soil. 



A soil supplied with available plant food. 



A warm soil. 



A ventilated soil. 



These are the most important facts about plant 

 growth so far as the plant grower is concerned. In 

 other words, these conditions which are necessary 

 for root growth and development are the most im- 

 portant truths of agriculture, or they are the founda- 

 tion truths or principles upon which all agriculture is 

 based. Having found these conditions, the next 

 most important step is to find out how to bring them 

 about in the soil, or, if they already exist, how to 

 keep them or to improve them. This brings us, 

 then, to a study of soils. 



