UTILIZING OUR SOIL RESOURCES — SALTER 321 



of farming have been followed on most farms since the very begin- 

 ning of American agriculture. The inherent productivity of the soil 

 has declined continuously, and is still going down. Gains from pro- 

 grams for soil conservation and from increased use of chemical fer- 

 tilizer have not offset losses from soil deterioration. 



Reversing the downward trend in soil productivity would give 

 another sharp rise in crop production. Herein lies one of our great- 

 est opportunities for expanding the capacity of American agriculture 

 to produce. 



SOIL IS A RENEWABLE RESOURCE 



No longer do wo consider soil as simple, dead, and sterile matter. 

 Our modern concept is founded on the understanding that soil under- 

 goes continuous change — some natural and some man-made. 



Soil is made up largely of small mineral particles. Yet chemical 

 changes are continually in process. Soil contains roots of living 

 plants, small animals, and billions of microorganisms (bacteria and 

 fungi). It is made up of a combination of solid inorganic matter, 

 dead organic matter, living organic matter, water, soluble salts, and 

 air. Also, climate, vegetation, and topography make for different 

 patterns of soils. Thousands of different soil types have been iden- 

 tified. Wide variations occur within a country, and usually the soil 

 pattern varies on individual farms. Also, there is great variation 

 in the kinds of crops that different types of soil will grow — and in 

 their response to management. 



Some soils are highly productive in their natural state, while other 

 virgin soils are relatively unproductive. The degree of inherent 

 productivity of any soil depends on the natural processes that build 

 it. In the Midwest, for example, the natural building process stocked 

 most soils with an abundant supply of organic matter and mineral 

 elements, leaving them highly productive. In the Southeast, on the 

 other hand, soils were developed under forests in a humid climate 

 with little freezing and much leaching, leaving the majority of them 

 acid in reaction, low in organic matter and mineral fertility, and 

 relatively unproductive. 



From our modern understanding of the natural processes that build 

 and change soils, two points of great significance are evolving: 



1. Some soils naturally infertile can be made highly productive. 

 Many fields once considered "worn out" are yielding crops abundantly, 

 and some where soil fertility was naturally too low for economic 

 production are being cropped profitably. In the eastern part of the 

 United States, the soil is much better today on many farms than it 

 ever was under natural conditions. 



2. Naturally fertile soils that have lost productivity through use 

 and abuse often can be rejuvenated. While the practical level of 



