Methods of Use of Fertilizers 193 



size of the particles, the coarser are deposited as gravel or 

 sand, in one place, and the finer particles are deposited in 

 another, making the clay. The lime enters partly into so- 

 lution and is deposited in another place, and so on, thus 

 giving us sandy soils, clayey soils and limy soils, all differ- 

 ing from each other in their amount and proportion of the 

 essential fertilizing constituents, as well as in their physical 

 qualities, the sandy and gravelly making the poorest 

 soils because the particles consist very largely of quartz, 

 and the remainder being poor in phosphoric acid or potash. 

 The clay soils are frequently rich in minerals containing 

 potash, and poor in those containing lime and phosphoric 

 acid ; and the limestone soils are poor in potash and rich 

 in lime, and frequently in phosphates. In addition to these 

 soils, there are those that are made up largely of vegetable 

 matter, due to the accumulation of decaying growths. 

 These are frequently rich in nitrogen and poor in all of the 

 essential mineral constituents. 



Hence it is that in the use of a commercial fertilizer, 

 at least for certain crops, a knowledge of the nature of soils 

 in respect to the possible deficient element is important, 

 in order that those which exist in abundance may not be 

 added to, but that they may be supplemented by such an 

 abundance of the deficient elements as to permit the ac- 

 quirement by the crops of those necessary for a maximum 

 growth. As a rule, potash is a very essential constituent 

 of manures for sandy soils, not only because all crops 

 require potash, but because they require it in relatively 

 large amounts, and because in sandy soils it is liable to 

 exist in minimum amounts. Potash fertilization, therefore, 

 is especially useful on sandy soils. On the other hand, in 

 clay soils, which, as a rule, contain a very considerable 

 proportion of potash as compared with sandy soils, the 



