The effects of such losses on crop yields are similar to those 
due to soil erosion by runoff water. The most fertile parts of 
the scil are removed, conveyed in the air for considerable dis-~ 
tances, and then deposited on the land, in cities and towns, or 
in the sea. Much of the soil removed is redeposited on farmland, 
where it remains available for use, However, much of it is 
deposited where no use can be made of it or where it creates 
major problems of removal. The dust storms, which represent 
the more serious cases of soil blowing, cause additional damage 
through abrasive action on crops, machinery, and farm equipment. 
Generelly limited to arid and semiarid areas, losses from soil 
blowing are widely distributed, but have reached the greatest 
magnitude in the Dust Bowl of northwestern Texas, northeastern 
New Mexico, western Kansas and Oklahoma, and eastern Colorado, 
Soil blowing in the humid areas, although less serious, does 
create acute local problems, particularly on drained and culti- 
vated organic soils (peat and muck) and on very sandy soils. 
Deterioration of Soil Structure 
While loss of favorable structure frequently accompmies soil 
erosion through the exposure of harsh, cloddy subsoils, it is 
also a widely prevalent censequence of cultivation even where 
no soil is lost. Yield reductions may be permanent in the ab= 
sence of proper soil management, but generally the condition can 
be corrected through a shift to fewer and more careful cultiva- 
tions and better rotations. Poor structure may develop at the 
surface (surface crusts), below the furrow slice (plow or tillage 
pans), or within the surface soil (puddling and compaction). 
Hard surface crusts develop mainly from the beating of rain- 
drops upon unprotected soil. Adverse effects on crops arise 
from (1) impeding of water infiltration with consequent increase 
in runoff and erosion, (2) interference with seedling emergence, 
and (3) injury to young plants upon cultivation. 
Plowpan formation is a frequent result of overcultivation of 
moist, medium-textured soils with implements the blades of which 
tend to compact the soil immediately below the furrow slice. 
Plowpans affect crop yields through resistance to root develop- 
ment and reduction in permeability to water. 
Puddling and compaction of the surface arise when soils are 
driven over or cultivated while still moist, with consequent 
reductions in yield from the unfavorable seedbed produced. The 
hoofs of grazing livestock may also cause some compaction. 
Structure deterioration occurs in varying degrees throughout 
the country. The most severe damage to crop production is 
generally on the medium-textured soils, particularly silt loams, 
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