Rejoinder to Comments on Minasny et al., 2017 Soil carbon 4 per mille Geoderma 292, 59–86

Minasny, Budiman; Arrouays, Dominique; McBratney, Alex B.; Angers, Denis A.; Chambers, Adam; Chaplot, Vincent; Chen, Zueng‐Sang; Cheng, Kun; Das, Bhabani S.; Field, Damien J.; Gimona, Alessandro; Hedley, C. B.; Hong, Suk Young; Mandal, Biswapati; Malone, Brendan; Marchant, Ben P.; Martín, Manuel; McConkey, B.G.; Mulder, Vera Leatitia; O’Rourke, Sharon; Richer-de-Forges, Anne C.; Odeh, Inakwu O. A.; Padarian, José; Paustian, Keith; Pan, Genxing; Poggio, Laura; Savin, I. Yu.; Stolbovoy, V. S.; Stockmann, Uta; Sulaeman, Yiyi; Tsui, Chun Chih; Vågen, Tor-Gunnar; Wesemael, Bas van; Winowiecki, Leigh A.

doi:10.1016/j.geoderma.2017.05.026

Cited by 41 publications

(22 citation statements)

References 41 publications

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“…There also appear to be differences of opinion as to whether the 4‰ goal is a specific target, an aspiration goal or even “more of a concept (or even a slogan)” as suggested by Minasny et al. ().…”

Section: Introductionmentioning

confidence: 99%

Major limitations to achieving “4 per 1000” increases in soil organic carbon stock in temperate regions: Evidence from long‐term experiments at Rothamsted Research, United Kingdom

Poulton

Johnston

Macdonald

et al. 2018

Global Change Biology

286

192

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We evaluated the “4 per 1000” initiative for increasing soil organic carbon (SOC) by analysing rates of SOC increase in treatments in 16 long‐term experiments in southeast United Kingdom. The initiative sets a goal for SOC stock to increase by 4‰ per year in the 0–40 cm soil depth, continued over 20 years. Our experiments, on three soil types, provided 114 treatment comparisons over 7–157 years. Treatments included organic additions (incorporated by inversion ploughing), N fertilizers, introducing pasture leys into continuous arable systems, and converting arable land to woodland. In 65% of cases, SOC increases occurred at >7‰ per year in the 0–23 cm depth, approximately equivalent to 4‰ per year in the 0–40 cm depth. In the two longest running experiments (>150 years), annual farmyard manure (FYM) applications at 35 t fresh material per hectare (equivalent to approx. 3.2 t organic C/ha/year) gave SOC increases of 18‰ and 43‰ per year in the 23 cm depth during the first 20 years. Increases exceeding 7‰ per year continued for 40–60 years. In other experiments, with FYM applied at lower rates or not every year, there were increases of 3‰–8‰ per year over several decades. Other treatments gave increases between zero and 19‰ per year over various periods. We conclude that there are severe limitations to achieving the “4 per 1000” goal in practical agriculture over large areas. The reasons include (1) farmers not having the necessary resources (e.g. insufficient manure); (2) some, though not all, practices favouring SOC already widely adopted; (3) practices uneconomic for farmers—potentially overcome by changes in regulations or subsidies; (4) practices undesirable for global food security. We suggest it is more realistic to promote practices for increasing SOC based on improving soil quality and functioning as small increases can have disproportionately large beneficial impacts, though not necessarily translating into increased crop yield.

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Section: Introductionmentioning

confidence: 99%

Major limitations to achieving “4 per 1000” increases in soil organic carbon stock in temperate regions: Evidence from long‐term experiments at Rothamsted Research, United Kingdom

Poulton

Johnston

Macdonald

et al. 2018

Global Change Biology

286

192

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“…Despite the variability of measured responses to improved management, conservation practices and climate change reported in the literature (Alexander, Paustian, Smith, & Moran, 2015;Bruce et al, 1999;FAO, 2011;IPCC, 1996;Lorenz & Lal, 2016;Minasny et al, 2017a), in most cases, measured C sequestration rates are less than 0.5 to 1 Mg C ha −1 yr −1 when long-term observational data (>20 yr) are considered. For the United States, for example, Chambers, Lal, and Paustian (2016) reported annual rates of 0.3-0.5 Mg C ha −1 for cropland and 0.04-0.21 Mg C ha −1 for grazing land, while long-term studies covering the globe as reviewed by Minasny et al (2017) point at an average annual rate of 0.2-0.6 Mg C ha −1 . Similar values, or best estimates, are used here for possible annual C gains in croplands and grasslands, by bioclimatic zone (M1, see Table 1).…”

Section: Assumptions and Scenariosmentioning

confidence: 99%

Technologically achievable soil organic carbon sequestration in world croplands and grasslands

Batjes

2018

Land Degrad Dev

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Reported potentials for sequestration of carbon in soils of agricultural lands are overly optimistic because they assume that all degraded cropland and grassland can be subjected to best management practices. Two approaches for estimating this potential are presented. Method 1 (M1) considers literature‐derived best estimates for annual soil organic carbon (SOC) gains (Mg C ha−1) by bioclimatic zone; Method 2 (M2) assumes an annual C increase of 3 to 5 promille with respect to present SOC mass (similar to the French ‘4 pour mille’ initiative). Four management scenarios are considered, capturing the varying level of plausibility of meeting the full technological potential. According to M1, achievable gains range from 0.05–0.12 Pg C yr−1 to 0.14–0.37 Pg C yr−1, with a technological potential of 0.32–0.86 Pg C yr−1. For M2, these are 0.07–0.12 Pg C yr−1, 0.21–0.35 Pg C yr−1, and 0.60–1.01 Pg C yr−1. Consideration of the technological potential only and use of a proportional annual increase in SOC (M2), rather than using best estimates for soil carbon gains by bioclimatic zone (M1), will provide too ‘bright a picture’ in the context of rehabilitating degraded lands and mitigating/adapting to climate change. Further, M2 assumes that possible C gains will be greatest where present SOC stocks are highest, which is counter‐intuitive. Although all measures aimed at increasing SOC content should be encouraged due to the creation of win‐win situations, it is important to create a realistic picture of the amount of SOC gains that are feasible based on bioclimatic and management implementation constraints.

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“…This initiative aims to increase the amount of OC in soils around the world, not only to reduce atmospheric CO 2 concentrations, but also to improve food production and mitigate soil degradation. The 4 per mille initiative has received many criticisms (Minasny et al, 2018), mainly related to the magnitude of achievable gains in SOC over the coming decades and social and economic constraints, despite the many benefits associated with increasing SOC stocks (Paustian et al, 2016;Chabbi et al, 2017;Soussana et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Assessing the Climate Regulation Potential of Agricultural Soils Using a Decision Support Tool Adapted to Stakeholders' Needs and Possibilities

Broek

Henriksen

Ghaley

et al. 2019

Front. Environ. Sci.

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Rejoinder to Comments on Minasny et al., 2017 Soil carbon 4 per mille Geoderma 292, 59–86

Cited by 41 publications

References 41 publications

Major limitations to achieving “4 per 1000” increases in soil organic carbon stock in temperate regions: Evidence from long‐term experiments at Rothamsted Research, United Kingdom

Major limitations to achieving “4 per 1000” increases in soil organic carbon stock in temperate regions: Evidence from long‐term experiments at Rothamsted Research, United Kingdom

Technologically achievable soil organic carbon sequestration in world croplands and grasslands

Assessing the Climate Regulation Potential of Agricultural Soils Using a Decision Support Tool Adapted to Stakeholders' Needs and Possibilities

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