Excerpts from the paper: Planning efforts underway to improve water quality of the nation's rivers and streams are a result of the Water Pollution Control Act of 1972. Section 208 of that act requires implementation of techniques and procedures recognized as having the ability to control nonpoint pollutants from agricultural lands. The pollutants identified include sediment from soil erosion, plant nutrients and pesticides. Controlled studies of crop management systems have demonstrated the

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... ess of various tillage systems to control one pollutant, sediment, from entering the nation's waterways. By volume, sediment is the single largest source of pollution of all waters of the nation. It is the by-product of soil erosion from all land, from streambanks and from drainage channels. Soil losses from agricultural lands have continued to accelerate in recent years because of more intensive crop management systems such as the monoculture. These management systems encourage additional tillage and agitation of the soil which furthers soil erosion. In order to provide the basis for a more systematic assessment of crop yields that can be expected from various conservation cropping practices, a survey was made of results obtained from recent site specific research studies. The survey was limited to the four Corn Belt states of Ohio, Indiana, Illinois and Iowa mainly because this section of the United States represents one of the most intensively tilled areas in the country. In addition to crop yields from the various conservation cropping practices a summary of the physical variables associated with each study was made and included soil loss whenever the information was available.