Long‐Term Continuous Corn and Nitrogen Fertilizer Effects on Productivity and Soil Properties

There are uncertainties about the sustainability of long‐term monoculture and N fertilizer use in corn ( Zea mays L.) production. This paper examines the effects of 50 yr (1958–2007) of continuous corn and N fertilizer use on corn yield, N use efficiency, soil pH, and organic matter content. Corn was harvested for grain with residues returned annually since 1958 on a Plano silt loam soil (fine‐silty, mixed, superactive, mesic Typic Argiudolls) near Arlington, WI (43°18’ N; 89°21’ W). The experimental design includes three N fertilizer rates (currently 0, 140, and 280 kg N ha −1 ) and two lime treatments (imposed in 1985) with four replications. Soil pH and organic matter content were measured periodically during the experiment. Average corn yields in N fertilized treatments increased dramatically (100%) over time with some of the highest yields occurring in the most recent years. Apparent N use efficiency (kg grain kg −1 N fertilizer) also increased over time, thus higher yields in recent years have not required greater N fertilizer use. Results suggest that both hybrid genetic improvement and improved management techniques contributed to the long‐term yield gain. Soil organic matter content was maintained or increased with long‐term N additions, and since 1985, lime treatments increased yields in 14 of 23 yr. Increasing productivity and N use efficiency along with stable or increasing soil organic matter suggest that long‐term continuous corn and N fertilizer use are sustainable practices. No evidence of a decline in productivity from long‐term corn monoculture or N fertilizer use was detected.