The Composition and Use of Fertilizers. 269 



some fertilizers give off a very offensive odor if allowed to become 

 damp, while they are comparatively free from disagreeable odors 

 if they are thoroughly dry. A strong odor in a fertilizer is an 

 indication that organic matter is decomposing and nitrogen is be- 

 ing lost and indicates weakness and loss rather than strength as a 

 fertilizer. 



Taking Advantage or Fluctuating Prices. — By watching 

 the market variations, it is possible to save more or less. It often 

 happens that lower prices prevail during that part of the year when 

 the farmer has most leisure. In any case, where home mixing is 

 practiced, it should be done before the beginning of the busy sea- 

 son. It is well for fanners early in winter to enter into corre- 

 spondence with three or four different parties to ascertain the 

 prices at which they can purchase the plant food materials they 

 desire. 



Purchase of Plant-Food Materials According to " Unit " 

 System and According to Ton System. — The more common 

 method employed by farmers in purchasing fertilizers, whether 

 mixed or unmixed, is to pay a given price for a ton of goods 

 without particular reference to the guaranteed composition, that 

 is, the amount of plant food contained in them. In purchasing 

 such high-grade materials as nitrate of soda, sulphate of am- 

 monia, dried blood, potash salts, etc., the composition is fairly 

 uniform and one may usually feel safe in purchasing by the ton. 

 However, in a variable material like tankage, for instance, it i< 

 unwise, to purchase by the ton, at least without a guarantee. 



The " unit " system is based on actual amounts of plant food 

 contained in the goods purchased. A unit of plant food is 1 

 per cent, for one ton, that is, twenty pounds. A unit of nitro- 

 gen is 20 pounds of nitrogen, a unit of available phosphoric acid 

 is 20 pounds of available phosphoric acid, and a unit of actual 

 potash is 20 pounds of actual potash. In quoting prices a dealer 

 might offer sulphate of potash at $1 per unit of actual potash 

 (20 pounds). That would mean five cents a pound. This is the 

 most satisfactory system of purchasing, for the consumer pays 

 for just the amount of plant food he buys. 



Making Club Fertilizers. — In some towns farmers club to- 

 gether and purchase their separate ingredients, each one doing 

 his own mixing himself. In other cases the club decides upon 

 a definite formula and sends out specifications to manufacturers 

 for furnishing the same already mixed and sacked, letting the 

 contract to the lowest responsible bidder. One of the most sue- 



