Asymbiotic nitrogen fixation is greater in soils under long-term no-till versus conventional tillage

Abstract

25A series of N-rate experiments was previously conducted in spring wheat, corn and 26 sunflower in North Dakota indicated that less N was required when fields were in 6-years or 27 more continuous no-till compared to conventional till. The objective of this study was to 28 determine whether part of the reason for the decreased requirement for N was the greater activity 29 of asymbiotic N-fixing organisms. Twelve paired-samplings were conducted in 2018. A surface 30 0-5cm deep sample was obtained in a long-term no-till field directly across the fence/road from a 31 similar soil in conventional till. Samples were incubated in an acetylene-reduction procedure to 32 estimate N fixation rate. Ten of twelve paired samplings had greater asymbiotic N fixation 33 compared to the conventional till counterpart. This indicates that long-term no-till soils support 34 greater N production from soil microorganisms than conventional till soils, which would result in 35 lower input costs to no-till farmers. 36 37 157 ¶Assumes 1.4 g soil cm -3 , ratio of C 2 H 4 : N 2 reduced is 3:1. Reduction under incubation 158 conditions. 159 160 Discussion 161Although several studies have indicated that greater asymbiotic N fixation is possible 162

Tillage intensity and plant rhizosphere selection shape bacterial-archaeal assemblage diversity and nitrogen cycling genes

“…Additionally, Obscuribacteria, a family within the phylum Cyanobacteria; Nitrosotaleaceae a family of archaea that can oxidize ammonia (Prosser and Nicol, 2015); and Phycisphaeraceaea, a family potentially involved in anammox (Rios-Del Toro, et al, 2018), were all higher in NT treatments compared to MP. Increased activity of free-living N2-fixing microorganisms may also occur in NT soils (Franzen et al, 2019). Changes to community composition in bulk soils managed under NT favor bacteria and archaea that cycle N and bypass the denitrification pathway.…”