Tillage reversal of long-term no-till soil increases crop yield while mitigating yield-scaled growing season GHG fluxes in a black Chernozem cropped to barley (Hordeum vulgare L.)

Abstract

Reversing land management from no-tillage to conventional tillage (tillage reversal, TR) may markedly alter soil greenhouse gas (GHG) emissions in soils with differing fertility levels. We studied the impact of TR and nitrogen (N) fertilization on CO₂ (total CO₂ flux and its components), N₂O and CH₄ fluxes, and area- and yield-scaled GHG fluxes over two growing seasons in central Alberta, Canada. A split-plot design was used with two levels of N, 0 (N0) vs. 100 kg N ha^− 1 yr^− 1 (N100), and tillage, long-term no-tillage (NT) vs. TR, treatments. The TR treatment increased total CO₂ fluxes (R_t), mainly attributed to the increased CO₂ production from microbial activity (R_h), with the R_h/R_t ratio ranging between 52 and 61% in this study. The area-scaled GHG fluxes ranged from 3.10 to 4.50 Mg CO₂-C eq. ha^− 1, while the yield-scaled GHG fluxes ranged from 1.36 to 5.84 kg CO₂-C eq. kg^− 1 grain. The area-scaled GHG fluxes were 0.74 Mg CO₂-C eq. ha^− 1 higher in the TR than in the NT treatment, and 14.7% higher in the N100 than in the N0 treatment. Nitrogen fertilization did not affect the yield-scaled GHG fluxes; however, the TR treatment lowered the yield-scaled GHG fluxes due to the significantly increased crop yield. Therefore, management decisions will have to consider whether the objective is to reduce total GHG emissions on an area basis or to minimize GHG emissions per unit crop yield. Our study shows that periodic tillage of long-term NT soils increased yield and reduced yield-scaled GHG emissions, suggesting that tillage reversal is practical if the management objective is to maximize yield and minimize GHG emissions per unit crop yield.