Long‐term effect of tillage and straw retention in conservation agriculture systems on soil carbon storage

Abstract

The main principles of conservationagriculture (CA) are minimal soil disturbance, permanent soil cover, diversification of crop rotations, and retention of crop residues. Tillage has been implicated with increased soil organic C (SOC) mineralization, but recently this has been contested. Residue retention and cover crops result in higher soil C inputs and are therefore expected to increase SOC. This study aimed to evaluate the effect of 17 yr of residue retention (with and without) and tillage (plowing and no-till) on soil C storage on two Danish sandy loam soils with different clay and SOC content under cool temperate humid climate conditions. Straw retention reduced bulk density at both sites. It also increased the C concentration with 0.47 mg C g -1 dry soil on average from 2002 to 2019, and SOC stocks in 2019 with 23 tonnes C ha -1 , on average, at the site with higher initial SOC content. The effect of straw retention on soil C was higher when the soil was plowed, and no significant effect was observed in no-till soils. Straw retention did not significantly affect C concentration at the site with low initial SOC. Tillage altered the C distribution in the soil profile, so that the C concentration in the upper layer (0-25 cm) was higher in the no-till soils, but did not significantly increase total C concentration in deeper layers (0-50 cm). Use of no-till and straw retention did not consistently affect crop yield across site-years, but the interannual variability was large, obscuring possible differences in yields.

Conservation Agriculture as a Sustainable System for Soil Health: A Review

“…High bulk densities cause root impedance and lead to poor crop emergence. There is no consensus regarding the effect of CA on soil bulk density, as some studies reported a higher soil bulk density with CA compared to CT [91,92], while others have not found significant differences [86,93] or reported lower soil bulk density in CA in comparison to CT [88,94]. These differences in bulk density in the different trials may be due in part to the typology of the farm.…”

The role of conservation agriculture on mitigating greenhouse gas emissions and enhancing carbon sequestration in soils

“…Denitrification appeared to be the primary pathway for N loss under continuous corn, whereas nitrifier-denitrification controlled N loss under rotation corn. • Straw retention increased soil C by 0.47 mg C kg −1 in a site with higher initial C but had no effect on a low C site in a 17yr tillage study in Denmark (Gómez-Muñoz et al, 2021). Straw retention did, however, decrease soil bulk density at both sites.…”

Effects of freeze-thaw cycles on soil structure under different tillage and plant cover management practices

“…Intact soil core samples corresponding to two tillage treatments and two plant cover treatments were extracted from the CENTS long-term crop rotation and tillage experiment at Aarhus University's department of Agroecology in Flakkebjerg (55 Hansen et al, 2015). The soil was classified as a Glossic Phaeozem (Krogh and Greve, 1999) with a sandy loam texture consisting of 14.7 % clay (<2 µm), 13.7 % silt (2-20 µm), 42.6 % fine sand (20-200 µm) and 27 % coarse sand (200-2000 µm), and an average organic C content of 9.8 mg C g − 1 (Gómez-Muñoz et al, 2021). The average bulk density in the top 100 mm was 1.30 Mg m − 3 in CT and 1.42 g Mg m − 3 in NT.…”