SOILS AND CROPS. 



21 



Tixe twelve primary constituents 

 found in plants and thus needed in 

 the soil are: — 



Nitrogen, 

 Potash, 



Phosphoric Acid, 

 Lime, _.., 



Water (Hydrogen ^", ' 

 and Oxygen), 



Iron Oxides, 

 Magnesia, 

 Sulphuric Acid, 



Carbon, 



Soda, 

 Chlorine. 



Nitrogen, phosphoric acid, potash 

 and lime are the constituents gener- 

 ally lacking in soils when they fail to 

 respond to the needs of crops. Either 

 one of these four Is likely to be de- 

 ficient. 



Classification of Soils. 



Sandy, under 10% of clay. 



Sandy Loam, 10% to 20% of clay. 



Loam, 20% to 30% of clay. 



Clay Loam, 30% to 50% of clay. 



Strong clay, over 50%. 



Marly, 5% to 50% calic carbonate. 



Humus, over 5% vegetable matter. 



The permanent fertility of a soil is 

 closely connected with its power of 

 retaining plant food. In 'clay soils 

 only traces of phosphoric acid are 

 found in the drainage water. 



Sandy soils being more open and 

 thus freer drained are of less natural 

 fertility and more dependent on imme- 

 diate supplies of manure. 



Humus or decayed vegetable mat- 

 ter, i.e., ploughed in clover, etc., 

 greatly increases a soil's capacity for 

 holding water. 



Water Capacity. 



Crops will not grow in soils perman- 

 ently saturated with water and from 

 which air is excluded. Best growth 

 obtained in soils one-half to two-thirds 

 saturated. The quantity of water a 

 '*il will ^old when fully drained de- 



termines its capacity for supplying a 

 crop with water. 



The finer the particles of the soil, 

 or the more porous, the greater the 

 amount of water held. When drained, 

 coarse sand and coarse gravel soils 

 hold the least water. 



Loss of nitrogen is far less when a 

 soil is under crop than in the case dt 

 a bare fallow. 



Depth of Plowing. 



Deep plowing of heavy land allows 

 rain to penetrate it, establishes drain- 

 agejn the surface soil and increases 

 its temperature. Shallow surface cul- 

 tivation preserves the soil water in 

 time of drought. Rolling increases the 

 moisture at the surface and the depth 

 to which the soil is warmed by the 

 sun. 



A crop can only use up a certain 

 amoimt of ready available plant food. 

 Therefore, the yaste as the soils be- 

 come richer is greater, and this point 

 should be borne in -mind. To farm 

 highly with profits demands more sci- 

 entific knowledge and more practical 

 skill than when a lower standard is 

 aimed at. The last ton of roots in a 

 big crop and the last few pounds of 

 weight on a very fat animal cost the 

 most to produce. 



Nature of Soils. 



Soils are made up of either very 

 fine or very coarse particles and are 

 classified accordingly. 



Soils may differ in degree of firm- 

 ness with which particles are held to- 

 gether. 



Sand is composed of simple separate 

 grains of large size. 



Clay is composed of extremely fine 

 granules. 



A soil is in good tilth when its gran- 

 ules are neither too fine nor too coarse 

 and when not too firmly cemented to- 

 gether. 



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^^^.^■^Jl'^^i^o^^l treatise on the Gasoline and Kerosene Engine, intended for the 

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