Major limitations to achieving 4 per 1000 increases in soil organic carbon stock in temperate regions: evidence from long-term experiments at Rothamsted Research, UK

A - Papers appearing in refereed journals

Poulton, P. R., Johnston, A. E., Macdonald, A. J., White, R. P. and Powlson, D. S. 2018. Major limitations to achieving 4 per 1000 increases in soil organic carbon stock in temperate regions: evidence from long-term experiments at Rothamsted Research, UK. Global Change Biology. 24 (6), pp. 2563-2584.

AuthorsPoulton, P. R., Johnston, A. E., Macdonald, A. J., White, R. P. and Powlson, D. S.
Abstract

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.

Keywords4 per 1000; Carbon sequestration; Climate change mitigation; Long-term experiments; Management practicies; Organic amendments; Rothamsted; Soil organic carbon
Year of Publication2018
JournalGlobal Change Biology
Journal citation24 (6), pp. 2563-2584
Digital Object Identifier (DOI)doi:10.1111/gcb.14066
Web address (URL)http://wileyonlinelibrary.com/journal/gcb
Open accessPublished as ‘gold’ (paid) open access
FunderBiotechnology and Biological Sciences Research Council
Funder project or codeThe Rothamsted Long Term Experiments [2017-2022]
Publisher's version
Accepted author manuscript
Output statusPublished
Publication dates
Online21 Jan 2018
Publication process dates
Accepted23 Dec 2017
Copyright licenseCC BY
PublisherWiley-Blackwell
Wiley
ISSN1354-1013

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