The economics of crop rotations is a research problem of central importance in Iowa agriculture. Although the major portion of Iowa cash farm income is derived from livestock, a greater share of the state\u27s gross value of agricultural products is attributable to crops than to livestock and livestock products. Livestock and livestock products provide the greatest part of the total cash income since the major portion of the hay and feed grains is not sold in the market but is, processed through livestock on the farms where the crops are produced. Livestock production adds 40 to 60 cents (depending on feed/livestock price ratios) to each dollar\u27s worth of crops fed to livestock in Iowa. The importance of crop production economics in Iowa...