Basso et al. (2018). Soil Organic Carbon and Nitrogen Feedbacks on Crop Yields under Climate Change

Page 1 of 5

emand for

food production is expected to increase as the world’s

population rises to 9 billion by 2050 (Wheeler and von Braun, 2013).

At the same time, increased climate variability, higher temperatures,

and projected frequent droughts and floods will make meeting this demand

more difficult (Sundström et al., 2014; FAO, 2016). Understanding the poten-

tial impacts and consequences of these climate risks has become a priority for

agronomists and policymakers across the globe (Denton et al., 2014; Basso et

al., 2015; Basso and Ritchie, 2018).

Agronomic inputs can increase yield and, at the same time, mitigate the cli-

matic and environmental footprint of agriculture (Basso et al., 2015; Basso and

Ritchie, 2018). Higher yields typically return a larger amount of crop residues

to the soil. It is important to maintain and increase soil organic carbon (SOC)

to improving soil-based ecosystem services and the overall sustainability of

agricultural systems (Jarecki et al., 2018). While there is a general agreement

on soil management practices that can help farmers achieve greater yields, the

interactions between management, soil, and climate remain poorly understood

(Godfray et al., 2010).

Process-based crop simulation models are important tools to assess and

predict the effect of nonlinear interactions between climate, soil, and manage-

ment on crop productivity and environmental outcomes such as SOC stock,

greenhouse gas emissions, and nitrate leaching (Jones et al., 2016). Models

have been used extensively to evaluate the effects of rising temperatures and

the increased frequency of extreme events on yields, and to design strategies

to mitigate and adapt to climate change (Byjesh et al., 2010; Rötter et al., 2011;

Donatelli et al., 2012; Asseng et al., 2013, 2014; Moradi et al., 2013; Rosenzweig

et al., 2014; Basso et al., 2015; Chenu et al., 2017). There remains, however, a

Soil Organic Carbon and Nitrogen Feedbacks

on Crop Yields under Climate Change

B. Basso,* B. Dumont, B. Maestrini, I. Shcherbak, G. P. Robertson,

J. R. Porter, P. Smith, K. Paustian, P. R. Grace, S. Asseng, S. Bassu,

C. Biernath, K. J. Boote, D. Cammarano, G. De Sanctis, J.-L. Durand,

F. Ewert, S. Gayler, D. W. Hyndman, J. Kent, P. Martre, C. Nendel,

E. Priesack, D. Ripoche, A. C. Ruane, J. Sharp, P. J. Thorburn,

J. L. Hatfield, J. W. Jones, and C. Rosenzweig

Science Society of America, and Soil Science Society of

America. 5585 Guilford Rd., Madison, WI 53711 USA.

This is an open access article distributed under the

terms of the CC BY license (https://creativecommons.

org/licenses/by/4.0/)

Supplemental material is available online for this article.

Agric. Environ. Lett. 3:180026 (2018)
doi:10.2134/ael2018.05.0026

Received

27 May 2018.

Accepted

9 July 2018.

*Corresponding author

(basso@msu.edu).

Agricultural

Environmental

Letters

Research Letter

Abstract:

A critical omission from climate change impact studies on crop yield is

the interaction between soil organic carbon (SOC), nitrogen (N) availability, and

carbon dioxide (CO

). We used a multimodel ensemble to predict the effects of

SOC and N under different scenarios of temperatures and CO

concentrations on

maize (

Zea mays

L.) and wheat (

Triticum aestivum

L.) yield in eight sites across

the world. We found that including feedbacks from SOC and N losses due to

increased temperatures would reduce yields by 13% in wheat and 19% in maize

for a 3°C rise temperature with no adaptation practices. These losses correspond

to an additional 4.5% (+3°C) when compared to crop yield reductions attributed

to temperature increase alone. Future CO

increase to 540 ppm would partially

compensate losses by 80% for both maize and wheat at +3°C, and by 35% for

wheat and 20% for maize at +6°C, relative to the baseline CO

scenario.

B. Basso, B. Maestrini, and D.W. Hyndman, Dep. of Earth

and Environmental Sciences, Michigan State Univ., East

Lansing, MI, USA; B. Dumont, Terra & AgroBioChem Dep.,

Gembloux Agro-Bio Tech–Univ. of Liege, Gembloux,

Belgium; B. Basso, I. Shcherbak, and G.P. Robertson, W.K.

Kellogg Biological Station, Michigan State Univ., East

Lansing, MI, USA; J.R. Porter, Montpellier Supagro, 2

Place Pierre Viala, 34060 Montpellier Cedex 02, France; P.

Smith, Institute of Biological and Environmental Sciences

School of Biological Sciences, Univ. of Aberdeen,

Scotland, UK; K. Paustian and J. Kent, Dep. of Soil and

Crop Sciences, Colorado State Univ., Fort Collins, CO,

USA; P.R. Grace, Institute for Future Environments,

Queensland Univ. of Technology, Brisbane, Queensland,

Australia; S. Asseng and J.W. Jones, Agricultural and

Biological Engineering Dep., Univ. of Florida, Gainesville,

FL, USA; S. Bassu, JRC, EU, Ispra, Italy; C. Biernath and

E. Priesack, Institute of Biochemical Plant Pathology,

Helmholtz Zentrum München-German Research Center

for Environmental Health, Neuherberg, Germany; K.J.

Boote, Dep. of Agronomy, Univ. of Florida, Gainesville,

FL, USA; D. Cammarano, The James Hutton Institute,

Invergowrie, Scotland, UK; G. De Sanctis, EFSA European

Food Safety Authority Parma, Italy; J.-L. Durand, INRA,

Unité de recherche pluridisciplinaire sur la prairie et

les plantes fourragères (URP3F), Lusignan, France;

F. Ewert, Institute of Crop Science and Resource

Conservation (INRES), Univ. of Bonn, Bonn, Germany;

S. Gayler, Institute of Soil Science and Land Evaluation,

Univ. of Hohenheim, Stuttgart, Germany; P. Martre,

INRA, UMR759, Lab. d’Ecophysiologie des Plantes

sous Stress Environnementaux, Montpellier, France;

C. Nendel, Institute of Landscape Systems Analysis,

Leibniz-Centre for Agricultural Landscape Research

(ZALF), Müncheberg, Germany; D. Ripoche, INRA,

US1116-AGROCLIM, Avignon, France; A.C. Ruane and

C. Rosenzweig, Climate Impacts Group, NASA Goddard

Institute for Space Studies, New York, NY, USA; J. Sharp,

The New Zealand Institute for Plant and Food Research,

Christchurch, New Zealand; P.J. Thorburn, CSIRO

Agriculture, St Lucia, Queensland, Australia; J.L. Hatfield,

USDA–ARS National Soil Tilth Lab. for Agriculture and the

Environment, Ames, IA, USA.

Core Ideas

•

SOC decline, due to increased temperatures,
reduces wheat and maize yields globally.

•

increase to 540 ppm partially compensates

yield losses due to increased temperatures.

•

Accounting for soil feedbacks is critical when
evaluating climate change impacts on crop
yield.

Abbreviations:

AgMIP, Agricultural Model Intercomparison and Improvement Project; SOC,

soil organic carbon.

Published online August 16, 2018

Page 2

Page 2 of 5

AGRICULTURAL & ENVIRONMENTAL LETTERS

critical omission from all these projections—that changes in

SOC occur concurrently with changes in air temperature and

concentration.

Basso et al. (2015) pointed out that most crop models pre-

viously used to predict climate change impact on yields did

not account for the concomitant changes in SOC and soil

nitrogen (N) content over time (Asseng et al., 2013, 2014;

Bassu et al., 2014; Basso et al., 2015), as the models were

reinitialized every year to same soil water, N, and C levels to

evaluate the effects of climate alone.

Given the importance of SOC and N to crop productiv-

ity and the potential for climate change to affect SOC stocks,

it is important to rectify this omission, especially since

post-COP21 there have been numerous initiatives aimed at

increasing SOC as a climate change mitigation measures (e.g.,

4 per 1000 initiative in France; https://www.4p1000.org).

We hypothesize that yields will decrease under higher

temperature because of the shorter vegetative period (Asseng

et al., 2014; Bassu et al., 2014), whereas an increase in CO

may partially offset yield decline by increasing CO

uptake

and water use efficiency (Leakey et al., 2009). We also

hypothesize that SOC levels will decline under future climate

scenarios because the higher temperatures will decrease bio-

mass and the amount of crop residues returned to the soil.

Due to the lower biomass produced, N removal by crops will

be lower, and with no reduction in N inputs will leave more

fertilizer N available for subsequent loss to the environment.

The objective of the study was to evaluate the feedbacks

from SOC and N to future maize (

Zea mays

L.) and wheat

(

Triticum aestivum

L.) yield under climate change.

Materials and Methods

To project soil C sequestration, inorganic N loss, and

yield, we used quantitative ensemble modeling to simulate

maize and wheat fallow rotations at eight sites around the

globe (Australia, Argentina, India, and the Netherlands for

wheat; Brazil, France, Tanzania, and the United States for

maize) under different scenarios of temperature and CO

concentrations. The sites were selected to represent a wide

range of soil and growing conditions for these two crops.

We simulated each site under different scenarios by testing

all combinations of increased local temperature (

3, 0, +3,

+6°C) and increased CO

concentration (360 and 540 ppm).

We first investigated whether the impact of increased tem-

perature on SOC and N dynamics varied across individual

model responses based on the ratio of simulated change in

crop yield per degree of temperature increase. We calculated

the median of the model ensemble separately for every site.

We used the coefficient of variation as an estimator of uncer-

tainty due to model differences. Each ensemble comprised

either seven wheat or five maize models with and without

the inclusion of SOC dynamics (Supplemental Table S1) to

evaluate crop model uncertainties for SOC, yield, soil N, and

water under increased temperatures and CO

. Model simula-

tions were generated for a 30-yr period to quantify the long-

term dynamics of SOC, water, and N with the same model

protocols as the maize and wheat pilots of the Agricultural

Model Intercomparison and Improvement Project (AgMIP)

(Rosenzweig et al., 2013), where the models had previously

been validated. The models were run using two distinct

modes. In the first (reinitialized mode), we reinitialized SOC,

soil N, and soil water annually to the same initial conditions

every year, as in the previous AgMIP studies (Asseng et al.,

2013; Bassu et al., 2014). In the second (continuous mode),

the same models were run continuously for 30 yr, allowing

the models to accumulate the effect of years of cultivation

on SOC, soil N, soil water, and crop yield. The differences

between reinitialized and continuous mode allowed us to

understand how yield losses were affected by SOC decline

under increased temperature and CO

increase compared

with yield decline due to temperature increase alone without

accounting for the SOC and N loss feedbacks.

Results

On average, our continuous simulations projected a

decrease in plant transpiration from

1 to

10 mm per degree

of temperature increase due to a shorter growing season,

smaller plants, and higher fraction of soil evaporation in

total evapotranspiration (Fig. 1). Simulated yields decreased

by 0.1 to 0.3 tonnes ha

for wheat and by 0.2 to 0.6 tonnes

for maize for every degree of local temperature increase.

We found a correlation between the simulated soil nitrate

content at the end of the season and temperature increase in

the different scenarios; more specifically, we found that an

increase in temperature determines an increase in soil nitrate

content at the end of the season. Values ranged from 2.5 (US

maize) to 29.3 (Australian wheat) kg N ha

(Fig. 1).

We found that uncertainty was at a minimum when we ran

the model under the baseline scenario and that uncertainty

Fig. 1. Modeled average 30-yr changes in (A) yield, (B) transpi-

ration, (C) soil nitrate, and (D) soil organic carbon (SOC) as a

function of mean temperature increase over the range 0, +3°C,

+6°C, under [CO

] baseline conditions (360 ppm) for wheat

(empty bars: AR, Argentina; AU, Australia; IN, India; NL, the

Netherlands) and maize sites (filled bars: BR, Brazil; FR, France;

TZ, Tanzania; US, United States). For each boxplot, the black dot

represents the median (50th percentile), while the bars span 25th

to 75th percentiles and lines span 10th to 90th percentiles of

model ensemble results.

Page 3

AGRICULTURAL & ENVIRONMENTAL LETTERS

Page 3 of 5

increased with increasing temperature. The increase in

uncertainties under increased temperature is a result of the

different approaches implemented by models to account for

the effects of increased temperatures on crop yield and on C

and N dynamics. Our results show uncertainties that are of

the same order of magnitude and corroborate the findings of

earlier models (Asseng et al., 2013; Bassu et al., 2014). All the

models agreed on the direction of change (Fig. 1).

The results of our simulations with the inclusion of SOC

indicate that increased temperature will reduce future aver-

age yield by 13% (+3°C) and 35% (+6°C) for wheat and by

19% (+3°C) and 32% (+6°C) for maize compared with base-

line simulations (Table 1). We attribute these yield reductions

under increased temperature mainly to the shorter effective

growing period due to higher temperature’s accelerating

plant development. When these yield losses were compared

with yields obtained by only increasing temperature without

the inclusion of SOC changes, the differences corresponded

to additional yield losses of 4% (+3°C) and 5% (+6°C) in

wheat and 5% (+3°C) in maize (Supplemental

Tables S4, S5).

Simulated SOC changes on average

decreased (relative to initial values) by 0.7 to

4.4% per year and per degree of temperature

increase. We found that SOC decreased over

time with increased temperatures, and sites

with the highest initial SOC content exhib-

ited the largest decrease (Fig. 2; Senthilkumar

et al., 2009). Under lower temperature sce-

narios (baseline and

3°C), as shown in Fig.

2, the French site gained SOC over time due

to increased residue inputs (baseline) and/or

slower decomposition (

3°C). However, all

sites lost SOC with increased temperatures.

With a 6°C temperature increase, the reduc-

tion in SOC content after 30 yr ranged from 10

to 65% of initial values for wheat and 20 to 45%

of initial values for maize. Under these high

temperature change scenarios, maize sites that

were initially below 1.5% SOC (i.e., Australia,

India, Brazil, France, and Tanzania) showed a

nonlinear change over time, with smaller rela-

tive changes occurring after the first years.

The cumulative difference between N input

(mineral N fertilizer applied, N from crop

residues) and the N removed from the system

(leached N at end of the growing season,

annual unused N, N used by the crop) indi-

cate that N losses exceed N input for all com-

binations of sites and temperature and that N

losses increased with temperature (Galloway

et al. 2004).

Discussion

Our results suggest that reductions in

residues returned to the soil, lower SOC

levels, and lower soil N availability pose

an additional threat to crop yields for

Table 1. Relative percentage changes of simulated yields (model

ensemble) for the different sites and temperature levels compared to

the baseline scenario. Negative values depict the inability of [CO

] to

compensate for the loss of yield associated to the concomitant impact

of soil organic C decline and temperature increase, while positive

values indicate a mitigation of yield losses.

Site†

Temperature change, [CO

] kept at 360 ppm

−3

Baseline

Wheat

4.13

0.00

12.89

34.93

28.20

0.00

17.74

41.08

3.07

0.00

16.58

47.82

0.67

0.00

3.90

16.86

Avg. wheat

7.48

0.00

12.78

35.17

Maize

12.50

0.00

5.51

22.98

39.27

0.00

13.44

20.06

4.65

0.00

38.98

60.70

6.15

0.00

18.93

25.23

Avg. maize

15.64

0.00

19.21

32.24

† AR, Argentina; AU, Australia; IN, India; NL, the Netherlands; BR, Brazil ;

FR, France; TZ, Tanzania; US, United States.

Fig. 2. Simulations of the soil organic carbon (SOC) stocks (0–25 cm) for the different

sites under scenarios with different temperature and constant CO

concentration

(360 ppm). The lines represent the median of the model ensemble predictions for the

site and scenario. The site abbreviations (a) for wheat are Argentina (AR), Australia

(AU), India (IN), and the Netherlands (NL) and (b) for maize are Brazil (BR), France (FR),

Tanzania (TZ), and the United States (US).

Page 4

Page 4 of 5

AGRICULTURAL & ENVIRONMENTAL LETTERS

key agricultural sites worldwide unless new adaptation

strategies (changes in planting dates, new cultivars, N

fertilization, disease prevention, and pest control) are

implemented.

Future temperature increases are expected to reduce

maize and wheat yields; however, results confirmed our

hypothesis that the concurrent increments of CO

will par-

tially compensate for these losses (Table 2), echoing a large

body of literature (Long, 1991; Kimball et al., 2002; Long et

al., 2006; Leakey et al., 2009). Increasing CO

concentration

to 540 ppm reduced losses due to temperature increase by

80% in wheat and by 81% in maize in the +3°C scenario and

by 35% (wheat) and 20% (maize) in the +6°C scenario. Lower

temperatures have the most detrimental effect for maize cul-

tivated in France (Supplemental Fig. S1); because this site is

the coldest among the ones in this study, a

3°C in tempera-

ture would prevent the plants from receiving enough degree

days to reach maturity (Bassu et al., 2014). On the opposite

side, an increase of 6°C would be most detrimental for maize

grown in Tanzania (Supplemental Fig. S1), the warmest of

our sites (Bassu et al., 2014).

We showed that the predictions from our model ensem-

ble agree with the current paradigm that increased tempera-

tures accelerate crop development and thereby effectively

shorten the growing season, consequently lowering yields,

biomass production, and crop residues returned to the soil.

Under higher temperature scenarios at nonirrigated sites,

the removal of N in the form of harvested grain will decline,

resulting in higher reactive N losses due to unused soil N

(Supplemental Fig. S9, S10, S11).

Results of this study also demonstrate that it is critical to

take into account changes occurring in the soil as the result

of management, as these changes will shape the design of

future strategies to adapt to and mitigate increased climate

variability and change globally.

Supplemental Material

Supplemental information is available online. The supplemental

material reports the simulations protocols, the multimodel

ensemble, and additional details on the uncertainty analysis and on

soil organic C and N dynamics under climate change.

Conflict of Interest Disclosure

The authors declare no competing financial interests. The views

expressed in this paper are the views of the authors and do not

necessarily represent the views of the organization or institution to

which they are currently affiliated.

Author Contributions

B.B. conceived and motivated the study. B.B., B.D., G.P.R, P.S.,

J.R.P., and K.P. led the writing of the paper; B.B., B.D., B.M, and

I.S. analyzed the data; S.A., F.E., P.M., J.-L. D., and S.B. analyzed

and provided the AgMIP wheat- and maize-pilots data; B.B., B.D.,

B.M, I.S.

G.P.R., J.R.P., P.S., K.P., P.R.G. S.A., S.B., C.B., K.J.B., D.C.,

G.D.S., J.-L.D., F.E., S.G., D.W.H, J.K., P.M., C.N., E.P., D.R., A.C.R.,

J.S. P.J.T., J.L.H., J.W.J., and C.R. carried out crop model simulations,

discussed the results, and contributed to writing the paper.

Acknowledgments

Support was provided by the UKAID for its primary financial

support to the Agricultural Model Intercomparison and

Improvement Project (AgMIP). Additional funding was provided

by USDA–NIFA under awards 2015-68007-23133, 2011-67003-

3025, and 2011-68002-30190, the FACCE JPI MACSUR project

(031A103B) through the metaprogram Adaptation of Agriculture

and Forests to Climate Change (AAFCC) of the French National

Institute for Agricultural Research (INRA), and the Swiss National

Science Foundation (project number 167689). We thank Anne

Stanton and two anonymous reviewers for very helpful comments

on an earlier draft.

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Table 2. Relative percentage changes of simulated yields when moving

from the baseline scenario ([CO

] = 360 ppm and

T = 0°C) to higher

temperature under and [CO

] of 540 ppm. Negative values depict

the inability of [CO

] to compensate for the loss of yield associated

to the concomitant impact of soil organic C decline and temperature

increase, while positive values indicate a mitigation of yield losses.

Site†

Temperature change, [CO

] increased to 540 ppm

−3°C

Baseline

Wheat

–

6.29

2.77

20.70

–

2.64

14.86

35.80

–

26.91

3.17

29.94

–

23.10

4.83

5.03

Avg. wheat

–

13.41

2.41

22.87

Maize

–

28.97

2.11

15.26

–

13.11

5.22

16.15

–

1.77

15.20

55.98

–

13.82

3.03

15.35

Avg. maize

–

13.53

3.82

25.69

† AR, Argentina; AU, Australia; IN, India; NL, the Netherlands; BR, Brazil ;

FR, France; TZ, Tanzania; US, United States.

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