Liebhardt, W., Andrews, R., Culik, M., Harwood, R., Janke, R., Radke, J., and S. Rieger-Schwartz. 1989. Crop production during conversion from conventional to low-input methods. Agronomy Journal 81(2):150-159.

Abstract: A 5-yr cropping system experiment was initiated in 1981 to study transition from a conventional agricultural system using pesticides and fertilizers to a low-input system. The site was primarily Comly silt loam (fine-loamy, mixed, mesic, Typic Fragiudalf) with 12% Berks shaly silt loam (loamy-skeletal, mixed, mesic, Typic Dystromesic, Ultic Hapludalf), in Berks County, eastern Pennsylvania. Three 5-yr rotations were compared. A conventional corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation (designated "conventional") was compared to two low-input rotations which utilized oat (Avena sativa L.), red clover (Trifolium pretense L.) and winter wheat (Triticum aestivum L.), in addition to corn and soybean. One low-input rotation used cattle manure as a nutrient source and produced forage crops in addition to cash crops (designated "low-input/livestock"), while the other used legume crops as a nutrient source, and produced a cash crop every year (designated "low-input/cash grain"). Corn grain yields in the low-input systems were 75% of conventional in 1981 to 1984, but yields were not significantly different in 1985. Weed competition and insufficient N limited low-input corn yields during the first 4 yr. Soybean yields in the low-input systems were equal to or greater than conventional all 5 yr. It is concluded that a favorable transition from input-intensive cropping to low-input systems is feasible, but only if crop rotations are used which include crops that demand less N and are competitive with weeds, such as small grain, soybean, or legume hay. Corn should be avoided for the first 3 to 4 yr.