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MISCELLANEOUS PUBLICATION NO. 1065. U.S. DEPARTMENT OF AGRICULTURE 



nearly as serious during the fifties as it was 20 or 

 25 years earlier. At Dodge City, Kans., in 1936-37, 

 there were 120 days of blowing dust. At the same 

 location in 1956-57, under comparable meteoro- 

 logical conditions, there were only 40 days of 

 blowing dust. 



Research lias developed a wind erosion predic- 

 tion equation used by action agencies to provide 

 technical guidance in farm and ranch planning. 



In expanding the research on the problems of 

 soil blowing in the Great Plains consideration 

 must be given to various concepts for describing 

 and delineating the influence of atmospheric wind 

 and turbulence on soil detachment and transport; 

 effect of wind and related atmospheric factors in 

 soil dry i tig and creation of soil surface conditions 

 susceptible to high rates of detachment; modifica- 

 tion of tillage practices and machines to provide 

 effective and lasting crop residues and soil cloddi- 

 ness conditions to resist soil detachment ; the toler- 

 ance of crop plants to wind abrasion ; the develop- 

 ment, and selection of better strains and varieties 

 of grasses and crops to tie down soils susceptible 

 to blowing; design of better windbreaks; and se- 

 lection of better shrubs and trees to serve as wind- 

 breaks. 



Much better information is needed on techniques 

 to curb dust production on large feedlots. 



Research has developed greatly improved 

 screens to permit continuous operation of cotton 

 gins while reducing lint fly. But much-improved 

 engineering technology is needed to effectively fil- 

 ter the air from cotton gin operations as well as 

 to handle trash without contaminating the air 

 with dust or smoke or carrying diseases and in- 

 sects back to the fields. 



The current emphasis by the Federal Govern- 

 ment to do whatever is feasible to attain clean air 

 over the United States must include research to 

 control or abate dusts from agricultural sources. 



Sediment 



Sediments are primarily soils and mineral par- 

 ticles washed into streams by storms. Although 

 most of the sediment comes from land, a relatively 

 small amount is contributed from the spoil banks 

 of mining operations and smelters. 



Some 4 billion tons of sediment are washed into 

 tributary streams in the United States each year. 



About one-fourth of this sediment is transported 

 to the sea. "Water erosion is the dominant problem 

 on 179 million acres of cropland and a secondary 

 problem on an additional 50 million acres. At least 

 half of the sediment is coming from agricultural 

 lands. Some 30 percent of total sediment delivery 

 arises as geologic erosion such as that found on 

 the tributaries of the Missouri, Colorado, Rio 

 Grande, Red, and Arkansas Rivers. For example, 

 the Badlands of South Dakota are a tremendous 

 source of geologically eroded sediment. Five to 

 ten percent of the silt delivered comes from for- 

 ests and associated rangelands. Streambanks erode 

 and streambeds degrade, but aggradation may 

 fully compensate for sediment losses. Urban, in- 

 dustrial, and highway construction sites and road- 

 banks also contribute eroded materials. Although 

 such sources make but a small contribution to the 

 national sediment delivery, they may contribute 

 over half of the silt to the streams in a local 

 watershed undergoing intensive construction 

 activity. 



Research conducted on many different soils vary- 

 ing in characteristics, slope, cover, and prevailing 

 climatic conditions provided a mass of empirical 

 data on soil loss as induced by rainstorms. The data 

 were subjected to complex mathematical analysis 

 by a digital computer which enabled the formula- 

 tion of a universal erosion equation. This equation 

 aids action agencies to predict what soil losses will 

 be on a given soil of specified slope, under varying 

 cropping conditions, with a given rainfall energy 

 input. 



Watershed research has shown that land cover 

 is the major deterrent to sediment delivery into 

 tributary streams. Extensive empirical informa- 

 tion has been accrued on the entrainment, trans- 

 portation, and deposition of sediments in the 

 upstream watersheds towards making valid pre- 

 dictions of sediment accumulation behind flood- 

 detention structures. 



Improved technology in logging and construc- 

 tion of forest roads has reduced sediment delivery 

 from forestry operations. 



Forestry research on the abatement of wild fires 

 (fires not started by man) has made a major con- 

 tribution in diminishing sediment delivery from 

 forested lands. Soil loss from a burned area is 

 frequently tremendous. 



