Publication

How does tillage intensity affect soil organic carbon? A systematic review

HADDAWAY Neal, JACKSON Louise, KÄTTERER Thomas, BRACHT JØRGENSEN Helene, THOMSEN Ingrid K, ISBERG Per-Erik, HEDLUND K, LUGATO Emanuele

2017

Overview

Background The loss of carbon (C) from agricultural soils has been, in part, attributed to tillage, a common practice providing a number of benefits to farmers. The promotion of less intensive tillage practices and no tillage (NT) (the absence of mechanical soil disturbance) aims to mitigate negative impacts on soil quality and to preserve soil organic carbon (SOC). Several reviews and meta-analyses have shown both beneficial and null effects on SOC due to no tillage relative to conventional tillage, hence there is a need for a comprehensive systematic review to answer the question: what is the impact of reduced tillage intensity on SOC? Methods We systematically reviewed relevant research in boreo-temperate regions using, as a basis, evidence identified within a recently completed systematic map on the impacts of farming on SOC. We performed an update of the original searches to include studies published since the map search. We screened all evidence for relevance according to predetermined inclusion criteria. Studies were appraised and subject to data extraction. Meta-analyses were performed to investigate the impact of reducing tillage [from high (HT) to intermediate intensity (IT), HT to NT, and from IT to NT] for SOC concentration and SOC stock in the upper soil and at lower depths. Results A total of 351 studies were included in the systematic review: 18% from an update of research published in the 2 years since the systematic map. SOC concentration was significantly higher in NT relative to both IT [1.18 g/kg ± 0.34 (SE)] and HT [2.09 g/kg ± 0.34 (SE)] in the upper soil layer (0–15 cm). IT was also found to be significant higher [1.30 g/kg ± 0.22 (SE)] in SOC concentration than HT for the upper soil layer (0–15 cm). At lower depths, only IT SOC compared with HT at 15–30 cm showed a significant difference; being 0.89 g/kg [± 0.20 (SE)] lower in intermediate intensity tillage. For stock data NT had significantly higher SOC stocks down to 30 cm than either HT [4.61 Mg/ha ± 1.95 (SE)] or IT [3.85 Mg/ha ± 1.64 (SE)]. No other comparisons were significant. Conclusions The transition of tilled croplands to NT and conservation tillage has been credited with substantial potential to mitigate climate change via C storage. Based on our results, C stock increase under NT compared to HT was in the upper soil (0–30 cm) around 4.6 Mg/ha (0.78–8.43 Mg/ha, 95% CI) over ≥ 10 years, while no effect was detected in the full soil profile. The results support those from several previous studies and reviews that NT and IT increase SOC in the topsoil. Higher SOC stocks or concentrations in the upper soil not only promote a more productive soil with higher biological activity but also provide resilience to extreme weather conditions. The effect of tillage practices on total SOC stocks will be further evaluated in a forthcoming project accounting for soil bulk densities and crop yields. Our findings can hopefully be used to guide policies for sustainable management of agricultural soils.

• Publisher: BioMed Central,BioMed Central Ltd,BMC
• Subject: Agricultural and Veterinary sciences / Agriculture / Analysis / Annan lantbruksvetenskap / bioactive properties / Carbon content / climate change / Climate Science / Conservation / Conservation tillage / conventional tillage / disturbed soils / Earth and Related Environmental Sciences / Ecosystems / Environment / Environmental Law/Policy/Ecojustice / Environmental Management / Environmental Policy / Environmental Sciences and Nature Conservation (including Biodiversity) / Farming / Forestry Management / Geovetenskap och relaterad miljövetenskap / Global temperature changes / Klimatvetenskap / Land management / Lantbruksvetenskap och veterinärmedicin / Markvetenskap / meta-analysis / Miljö- och naturvårdsvetenskap (Här ingår: Biodiversitet) / Natural Sciences / Naturvetenskap / Other Agricultural Sciences / Plough / reduced tillage / soil organic carbon / soil profiles / soil quality / Soil Science / Soil structure / Soils / Systematic Review / Till / topsoil / weather