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Comparison of Soil Properties under Continuous Corn Grain and Silage Cropping Systems¹

Continuous corn (Zea mays) harvested for grain only, has been subjected to much study. There is little information available, however, as to the effect on such properties as soil pH, organic matter, available P, and exchangeable K when the entire plant is harvested. We compared these soil properties on plots of continuous corn grain and corn silage as part of a rotation-fertility experiment established in 1957 on a Typic Hapludol soil. Subplot treatments were four levels of applied N—O, 45, 90, and 135 kg/ha. We applied 17 kg/ha of P each year to all plots during the first 4 years of the study and 26 kg/ha for the remaining 15 years. Until 1974, plots received only nominal quantities of K (5 kg/ha) as starter fertilizer. After 1974, four rates of K were applied—52, 112, 168, and O kg/ha. Soil N and C declined over time under both cropping systems. The original level of soil organic matter was 4.5%, and after continuous removal of only the grain from plots, the soil organic matter declined to 4.1%. Organic matter declined to 3.7% on plots from which all top growth was removed. Exchangeable K levels declined rapidly during the first few years of corn production and then stabilized with corn silage plots stabilizing at 71 ppm and corn grain plots at 100 ppm. Application of 26 kg/ha of P each year resulted in a rise in soil P. Soil acidity and lime requirements were directly related to the rate of N fertilization.

Key Words: Soil organic matter decline • Continuous corn • Corn grain vs. corn silage

² Research assistant, professor of agronomy, and professor of agronomy, Iowa State Univ., respectively. Present address of Barnhart: Terra Eastern Corp., 1709 W. Main St., Sun Prairie, WI 53590.

Received for publication February 13, 1978.