456 MISCELLANEOUS FARM SUBJECTS 



deficient forms of plant food. Mixed animal manures are all com- 

 plete, or general, fertilizers. Green crops plowed under are com- 

 plete. The artificial fertilizers, whether commercial or chemical, 

 are complete or incomplete, according as they are mixed from raw 

 materials containing the three forms of plant food, or as they lack 

 one or more of these. A fertilizer is said to be indirect when it does 

 not contain deficient plant food, but in some way acts on the soil 

 so as to hasten the change of unavailable plant food in the soil into 

 available, that is, they increase the natural capacity of the soil. 

 Lime, gympsum, salt, etc., so far as they have any action, belong to 

 this class; others, like ashes, and especially leached ashes, are both 

 direct (furnishing plant food) and indirect. 



Land-plaster, gypsum or calcium sulphate, are different names 

 for the same compound. Gypsum or land-plaster is nothing more 

 than the sulphate of lime rock which has been ground exceedingly 

 fine. When limestone is burned the resulting product is calcium 

 oxide or quicklime, sometimes called stone-lime. When exposed to 

 the air it becomes air-slaked and is then calcium carbonate or car- 

 bonate of lime. 



The so-called complete fertilizers are commonly made by mix- 

 ing two tons of acid phosphate with two tons of filler containing 

 small amounts of nitrogen and potassium. The most popular filler 

 is the decayed peat from bogs. 



The terms high grade and low grade as applied to fertilizers 

 are neither absolute nor very well defined. It is customary to speak 

 of those fertilizers containing a relatively large amount of plant 

 food per ton as high grade, and those with a relatively small amount 

 as low grade. Another distinction is made on the basis of the kind 

 and quality of the materials of which the fertilizer is made up. If 

 the high grade standard materials like nitrate of soda, ground bone, 

 acid phosphate and muriate of sulphate of potash are used exclusively 

 in its making the fertilizer is said to be high grade, while if the 

 cheaper, inferior and less soluble materials like garbage tankage, 

 wood ashes and kainit are used, the fertilizer is called low grade. 

 Sometimes any complete fertilizer containing less than 2 per cent of 

 nitrogen is called low grade. As regards price it may be said that 

 complete fertilizers which retail for $30 per ton or less are low grade ; 

 those retailing from $30 to $38 are medium grade, and those selling 

 for more than $38 are high grade. 



Whether it is more economical to buy a high grade or a low- 

 grade fertilizer is an important question, but unfortunately it is one 

 not difficult to answer. All fertilizers should be bought on the 

 basis of the amount of available plant food they contain. A ton 

 of high-grade goods will contain a larger amount of plant food than 

 will a ton of low grade, but because the price of the latter is low and 

 therefore attractive, and because to many people a fertilizer is a fer- 

 tilizer, regardless of its composition, many tons of these low-grade 

 goods are sold annually. 



Concentrated high grade materials necessarily command a 

 higher price, but the difference is not always proportional to the 



