Asymbiotic Nitrogen Fixation is Greater in Soils under Long‐Term No‐Till Versus Conventional Tillage

Abstract

A series of N-rate experiments previously conducted in spring wheat, corn, and sunflower in North Dakota indicated that less N was required when fields were in six years or more continuous no-till compared to conventional till. The objective of this study was to determine whether part of the reason for the decreased requirement for N was the greater activity of asymbiotic N-fixing organisms. Twelve paired-samplings were conducted in 2018. A surface 0- to 5-cm deep sample was obtained in a long-term no-till field directly across the fence or road from a similar soil in conventional till. Samples were incubated in an acetylene-reduction procedure to estimate N fixation rate. Ten of twelve paired samplings had greater asymbiotic N fixation compared to the conventional till counterpart. This indicates that long-term no-till soils support greater N production from soil microorganisms than conventional till soils, which would result in lower input costs to no-till farmers.