Yield and nitrogen uptake of monocropped maize from a long-term tillage experiment on a poorly drained soil

Abstract

Little information is available on the long-term impact of tillage systems on grain yield and nitrogen (N) uptake of maize ( Zea mays L.) in the upper Midwest region of the USA. An 11 year (1982–1992) study comparing the effects of continuous autumn moldboard plowing (CT) vs. no-tillage (NT) on yield and N removal of monocropped maize was conducted on a poorly drained, well-tiled Webster clay loam soil in southern Minnesota, USA. Maize was fertilized each spring with ammonium nitrate (NH 4NO 3) at the rate of 200 kg N ha −1. Lower soil temperatures and an apparent increase in surface soil density associated with NT resulted in delayed silking by about 6 days and 25 g kg −1 wetter maize grain at harvest compared with CT during the 11 year period. Grain yield and N removal in the grain were consistently greater for CT than for NT owing to a combination of immobilization of surface applied N, lower spring soil temperatures, and surface soil consolidation limiting the root growth of plants leading to less N uptake with NT. Maize grain yield averaged 8.64 Mg ha −1 with CT and 7.33 Mg ha −1 with NT during the 11 year period. In the last 4 years of the study maize grain yield with CT averaged 2.46 Mg ha −1 (40%) more than with NT. Soil samples collected to a 22.5 cm depth in 1987 after 6 years of continuous tillage indicated significant reduction in pH in the top 2.5 cm of NT soil owing to nitrification of NH 4 + in the surface-applied fertilizer N and mineralization of plant residue. Significant accumulation of P in the surface soil (top 2.5 cm) also occurred in the NT soil, owing to deposition of P by residue on the soil surface. Plowing the established NT plots after 11 years resulted in a trend towards increased yield and N uptake compared with CT plots in the residual year (1993). Results from this long-term study indicate that CT is superior to NT for maize production on these poorly drained soils, especially when stress conditions of excess rainfall and/or growing season temperature extremes occur.