SOIL MANAGEMENT 3 



tive amounts of these different groups vary widely in different 

 soils, the relative predominance of the fine and the coarse par- 

 ticles determining whether a soil shall be classed as fine tex- 

 tured or as coarse textured. Soils that contain a large propor- 

 tion of clay are called clay soils ; those containing a large pro- 

 portion of sand are classed as sandy soils ; those that are inter- 

 mediate are called loam soils. A loam with a slight excess of 

 clay is known as a clay loam; one with an excess of silt a silt 

 loam. 



Various other names, such as sandy loam, fine sandy loam, or 

 gravelly loam, are applied to soils of different texture. In the 

 soil survey reports certain proj^er names are prefixed to further 

 describe certain soil types, as Leonardtown Loam, Miami Clay 

 Loam, Cecil Clay, and Penn Shale Loam. The coarser soil has 

 less pore space than the fine textured soil, hence it has a greater 

 weight per cubic foot. A cubic foot of dry sandy material weighs 

 from one hundred to one hundred and ten pounds ; of loam from 

 seventy-five to ninety pounds ; and of clay soil sixty to seventy 

 pounds. The average soil is usually estimated as weighing two 

 million pounds per acre of soil taken to the bottom of the plow 

 line, or about six and two-thirds inches. The term "heavy 

 soil", however, is frequently used when referring to a soil that 

 is difficult to work, such as a clay or a clay loam. Such soils are 

 difficult to work because they are sticky and plastic Avhen wet 

 and become very hard when dry. On the other hand, sandy soils 

 are called ''light" by the farmer because they are easily worked. 



The fact that certain classes of crop plants are better adapted 

 to certain kinds of soils does not mean that these crops cannot 

 be grown on other soils, but the successful farmer should select 

 the crops that can be produced most profitably on his particular 

 land. However, by the intelligent use of lime, manure and good 

 cultural methods he may fit his land for crops to which it is not 

 naturally well adapted. For instance, by the application of lime 

 and the plowing down of green manuring crops or heavy appli- 

 cations of stable manure a heavy clay soil may be changed to a 

 friable loam. On the other hand, the use of large amounts of 

 organic matter on a sandy field will increase its xuoisture hold- 

 ing capacity and make possible the gro\\nng of crops that are 

 not naturally well suited to sandy land. 



AYlien the fine particles of the soil are grouped together in 

 granules they form a crumb structure that makes the soil loose 

 and friable. It is then said to have good tilth or to be in a good 

 physical condition. If these granules or crumbs become ]-)roken 



