No-tillage and noninversion tillage comparisons across wheat nitrogen rates in Alabama

Abstract

Minimizing surface and deep tillage operations for wheat (Triticum aestivum L.) production may promote soil quality, but productivity and nitrogen (N) rate requirements need to be examined for these systems across Alabama Coastal Plain soils. A three-year experiment was conducted at three locations to (1) compare noninversion and no-tillage wheat production and (2) determine if N requirements across tillage systems should be modified. Each experiment (nine site-year comparisons) consisted of a split-plot design with tillage as the main plot and six fall and spring applied N fertilizer combinations as subplots, replicated four times. Tiller densities, tiller N concentrations, tiller biomass, wheat yields, grain crude protein, grain N use efficiency, and net returns were evaluated. Tillage system and fall N had no effect on tiller density or tiller N concentrations, except for 8% greater tiller N concentrations (P = 0.0842) for noninversion tillage compared to no-tillage at one location. Noninversion tillage also produced 23% more tiller biomass (P = 0.0040) compared to no-tillage at only one location. At two of the three locations, wheat yield response (P = 0.0764; P = 0.0313) varied up to 12%, but was inconsistent between tillage systems, while tillage system had no effect on grain crude protein and grain N use efficiency. The 134 kg N ha⁻¹ rate produced 17% (P ≤ 0.0001) and 30% (P ≤ 0.0001) yield increases, averaged over tillage systems, for the 67 and 101 kg N ha⁻¹ rates at the tillage responsive locations. No-tillage produced 11% greater net returns (P = 0.0238) than noninversion tillage for one location, while noninversion tillage produced net returns nearly six times greater (P = 0.0434) than no-tillage for the other location. Although net returns for the 101 and 134 kg N ha⁻¹ rates were equivalent, net returns were nearly double for the 134 kg N ha⁻¹ rate compared to the 101 kg N ha⁻¹ rate at one location. No-tillage produced equivalent yields compared to noninversion tillage at two of the three locations, but net returns for no-tillage were only positive for one location. The 134 kg N ha⁻¹ rate was required to maximize wheat production, but net returns indicated no advantage for additional N at the responsive locations, despite differences between N rates. No-tillage may enhance soil quality benefits, but yield increases and net returns were negligible compared to noninversion tillage across the Coastal Plain of Alabama.