THE POTATO ^ 215 



It Is often best to buy the elements singly, and 

 with a guarantee as to the contents of available 

 plant food. There are ways of manipulating 

 mixtures so as to puzzle the buyer, and at the 

 same time permit the seller to keep within the law. 

 In buying combined fertilizers the cost of mixing, 

 handling, and advertising must always be added 

 and paid for by the buyer. 



In order to maintain and build up virgin fertility 

 and soil condition a grower should be continually 

 adding stores of vegetable matter and such mineral 

 or organic elements as will probably be depleted 

 first. The latter can be applied in forms that are 

 available at once or in less soluble forms where the 

 usable fertihty becomes available gradually. 



In the countries of Europe where the best results 

 are obtained, and in this country where growers 

 have given the most careful attention to the busi- 

 ness, the highest importance is placed on the use 

 of the decaying root systems of strong growing 

 plants for fertilizing material and for keeping the 

 soil in good condition. Sir John Lawes, the 

 eminent British farmer and experimenter, said: 

 "It is the physical condition of the soil, its per- 

 meabiUty to roots, its power of absorbing and 

 radiating heat that is of more importance than its, 

 strictly speaking, chemical composition. " 



An interesting article on the value of green 

 manures is given by R. W. Thatcher in "Bulletin 

 32" of the Washington Agricultural Experiment 

 Station. It follows: 



"Soil is a mixture of inorganic material — i. e., 

 rocks or mineral substance broken down into more 

 or less fine particles — with organic matter — i. e., 

 decayed or decaying material which has once been 



