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Journal of Soil and Water Conservation
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Soil organic matter content and crop yield
Rattan Lal
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MARCH/APRIL 2020—VOL. 75, NO. 2
JOURNAL OF SOIL AND WATER CONSERVATION
FEATURE
doi:10.2489/jswc.75.2.27A
Rattan Lal
Soil organic matter content and crop yield
M
ost agricultural soils are
depleted of their soil organic
matter (SOM) reserves. A
severe loss of SOM content may degrade
soil functionality, its capacity for provi-
sioning of essential ecosystem services, and
soil health. Therefore, restoration of SOM
content in soils of agroecosystems may
reverse the degradation trends, enhance
ecosystem services (Banwart et al. 2015),
and advance Sustainable Development
Goals of the United Nations. (Lal et al.
2018a). Increase in SOM content may also
partially replace the use of chemical fer-
tilizers and supplemental irrigation, while
restoring the environment.
Some critical questions to be objec-
tively addressed regarding the restoration
of SOM include the following:
1. Is there a critical limit or range of
SOM content for soils of temperate
and tropical climates below which the
crop yield declines?
2. If such a limit/range can be established,
what are its principal determinants?
3. Can an increase in SOM content of a
severely depleted soil lead to increase in
crop yield under both nutrient/water
limiting and sufficient conditions?
4. Can any positive impact of increase
in SOM content be masked by use
of chemical fertilizers and supple-
mental irrigation?
5. Is restoration of SOM content a
resource-saving (i.e., land, water,
energy) option?
Therefore, the objective of this article is to
deliberate the impacts of SOM content on
crop yield under diverse climate, soil, land
use, and management systems.
SOIL ORGANIC MATTER CONTENT
AND SOIL HEALTH
Healthy soils are important to grow-
ing healthy crops, raising healthy animals,
and supporting a healthy human popu-
lation through nutritionally balanced
diets and environmentally healthy habi-
tats. Favorable SOM content is critical
to attaining such a vital interconnectivity.
The importance of SOM content to crop
yield has been known to ancient civiliza-
tions for millennia (Manlay et al. 2007),
and to soil scientists for at least two cen-
turies (Feller et al. 2012). In the modern
era, Allison (1973) vividly described the
significance of SOM content to crop
production, which paved the way for a
growing interest in the study of global
terrestrial soil organic carbon (SOC)
sequestration (Feller and Bernoux 2008;
Lal et al. 2018b), and processes affecting its
stabilization (Six et al. 2006; Dungait et al.
2013; Paul 2016).
SOM content affects crop yield
through its role in enhancing and sustain-
ing soil quality (Reeves 1997) and soil
health (Lal 2016). SOM content is intri-
cately interlinked with other physical,
chemical, and biological properties and
processes. A long-term study in eastern
Europe (the Czech Republic, Slovakia,
and Poland) indicated that regular appli-
cations of organic manure and of manure
plus chemical fertilizers optimized soil
quality, stabilized crop yield, and enhanced
adaptation to climate change (Menšík et
al. 2019).
SOM content is a critical indicator of
soil health through positive impact on soil
properties and processes (Doran and Zeiss
2000). In the context of agronomic pro-
ductivity, two key properties impacted by
SOM content are (1) plant available water
capacity (PAWC) and (2) plant available
essential nutrients, especially nitrogen (N).
Plant Available Water Capacity.
SOM
content affects aggregation (Kemper
and Koch 1966), porosity and pore size
distribution, and relative proportion of
retention pores that retain water at field
moisture capacity. For the 50-year period
between 1940 and 1990, the general con-
sensus among soil physicists had been that
SOC increases water retention both at
field capacity and at permanent wilting
point with no net gains in PAWC (Feustal
and Byers 1936; Baver 1940; Petersen et
al. 1968).
Presently, however, there are two views
about the impact of SOM content on
PAWC: (1) that it has minor or no impact,
Rattan Lal
is a distinguished university pro-
fessor of soil science and is the director of the
Carbon Management and Sequestration Center
at The Ohio State University, Columbus, Ohio.
and (2) that it has a major impact. In UK
soils, Gregory et al. (2009) reported that
reduction in SOM content from 7% to
3% can reduce soil water retention by up
to 10%. Similar observations on decline
of water retention by decrease in SOM
content were reported by Johnston et al.
(2008). Decline in PAWC by reduction
in SOM content is partly attributed to
decline in aggregate stability. Bauer and
Black (1992) reported that the loss of
soil productivity by erosion in the north-
ern Great Plains may be due to decline
in nutrients and biological activity rather
than from a decline in PAWC. On the
basis of meta-analysis of 60 published
studies, Minasny and McBratney (2018)
reported that increase in SOM content has
a small effect on PAWC.
However, there are others who have
reported a strong effect of SOM content
on PAWC (Bouyoucos 1939; Salter and
Haworth 1961; Salter and Williams 1963;
Petersen et al. 1968; Bryant 2015). Hudson
(1994) reported highly significant positive
correlations between SOM content and
PAWC for a range of soil textural groups
and concluded that in all textural groups, as
SOM content increased from 0.5% to 3%,
PAWC of soil more than doubled. Williams
et al. (2016) recommended investing in
restoration of SOM content to enhance
PAWC and mitigate downside risks and
volatility in rainfed corn (
Zea mays
L.)
in the United States. In Sierra Nevada,
California, United States, Ankenbauer and
Loheide II (2017) reported that increase
in water retention by SOM contributes as
much as 8.8 cm (3.46 in) to transpiration,
or 35 additional water stress–free days. Even
if the increase in PAWC by increase in
SOM content is small, it may be of critical
importance to crop growth between peri-
ods of rainfall, especially in dryland farming
(Johnston 1986).
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JOURNAL OF SOIL AND WATER CONSERVATION
MARCH/APRIL 2020—VOL. 75, NO. 2
Plant Available Nutrients.
Increase in
SOM content can also affect crop yield by
supplying plant nutrients, especially under
nutrient-limiting environments, and with
low inputs of chemical fertilizers. Bauer
and Black (1992) attributed the decline in
productivity of degraded soils to decline in
nutrients. Schjønning et al. (2018) reported
a positive effect of SOM on reduction of
mineral N needed to obtain the potential
crop yield and concluded that SOM does
add to crop production other than what can
be attributed to nutrient supply capacity.
It is the nutrient supplying capacity
of SOM upon its decomposition that has
raised the question of hoarding/saving it
versus using it (Janzen 2006). If the hoard-
ing versus saving role of SOM is attributed
to different fractions (fast cycling versus
slower cycling) (Wood et al. 2016), then
such a differential response of different
fractions would resolve this seemingly
apparent conflict. In the United Kingdom,
Johnston et al. (2008) observed that the
loss of SOM content can reduce the
exchange of some essential plant nutri-
ents (N, phosphorus [P], and sulfur [S]),
and increase of SOM content can sup-
ply N, P, and S for plant growth (Johnston
1986). SOM content also affects nutrient
supply by increasing the cation exchange
capacity, especially in soils of the tropics
(Ramos et al. 2018). A severe loss of SOM
can also lead to release of some toxic ele-
ments because of decline in chelation and
adsorption capacity of soil (Griffiths et al.
2005; Gregory et al. 2015). Under semi-
arid environments in China, Liu and Zhou
(2017) concluded that chemical fertilizers
alone are not sufficient for achieving high
yield, and they recommended that add-
ing manure is essential to improving soil
fertility. Synergistic effects of manuring
and chemical fertilizers on wheat (
Triticum
aestivum
L.)/cereal yield have also been
reported by others (Arrieche-Luna and
Ruiz-Dager 2010; Aula et al. 2016).
SOIL ORGANIC MATTER CONTENT
AND CROP YIELD
Because of numerous complex and inter-
acting factors, it is also difficult to establish
a direct cause-effect relationship between
crop yield and SOM content. Under field
conditions, where crop yield is affected
by numerous factors including biotic and
abiotic stresses, the direct cause-effect rela-
tionship is also confounded by the mutual
enhancement of crop yield and the SOM
content. The data in table 1 on cotton
(
Gossypium hirsutum
L.) yield from a long-
term experiment in Auburn, Alabama,
United States, is a pertinent example of
the complexities involved. Apparently,
the SOC content and cotton yield (from
1986 to 1995) are highly correlated (see
figure 1). However, the beneficial effects
of rotation, cover cropping, and fertilizer
N use cannot be isolated from those of
the increase in SOC content, and such
effects must be accounted for. A global
meta-analysis performed by Oldfield et al.
(2019) indicated potential yield increases
of 10% ± 11% for maize and 23% ± 37%
for wheat with increase in SOM content.
Oldfield and colleagues concluded that
enhancing SOM stocks in degraded soils,
and in those where a large yield gap exists,
can narrow the yield gap. These yield
increases amount to abridging the yield
gap of 30% for maize and 55% for wheat,
while also reducing the fertilizer inputs
by 5% to 7%. Oldfield and colleagues
also observed that higher concentrations
of SOC are associated with greater crop
yields up to an SOC concentration of 2%,
and that led to decreased inputs of fertil-
Mean cotton yield (kg ha
–1
)
Treatment
SOC content (g kg
–1
)
1896 to 1905
1986 to 1995
Continuous cotton
•No legume cover crop
3.9
896
1,042
•Legume cover crop
7.5
963
2,498
•Fertilizer N*
5.4
—
2,083
2-year rotation
•Legume cover crop
8.2
974
2,565
•Legume cover crop
10.0
997
2,867
+ fertilizer N*
3-year rotation
10.1
829
2,509
*Fertilizer nitrogen (N) = 134 kg ha
–1
y
–1
.
Table 1
Effect of soil organic carbon (SOC) concentration on yield of cotton in the Old
Rotation Experiment, Auburn, Alabama, United States (adapted from Reeves [1997]).
0 2 4 6 8 10 12
3,500
3,000
2,500
2,000
1,500
1,000
500
0
SOC content (g kg
–1
)
Mean cotton
yield
(kg ha
–1
)
y
= 231.14
x
+ 523.28
R
2
= 0.79
Figure 1
Effect of soil organic carbon (SOC) concentration on yield of cotton in the Old
Rotation Experiment, Auburn, Alabama, United States (adapted from Reeves [1997]).
Page 4
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MARCH/APRIL 2020—VOL. 75, NO. 2
JOURNAL OF SOIL AND WATER CONSERVATION
izer and irrigation. In Denmark, Ghaley et
al. (2018) concluded that SOC level had a
significant effect on grain yield of wheat
and aboveground biomass at only 0 to
100 kg N ha
–1
(0 to 89.2 lb N ac
–1
), and
its effect decreased with increasing rates
of N. Further, PAWC was also positively
correlated with SOC content. It increased
with increase in SOC content up until
0.7%, and PAWC increase was small for
the 0.7% to 2.0% SOC range (Ghaley et
al. 2018). In contrast, several studies have
suggested no effects of SOM content on
crop yield (Oelofse et al. 2015; Wei et al.
2016; Hijbeek et al. 2017) and have sup-
ported the hypothesis that it is difficult to
separate the effects of SOM on crop yield
from those of nutrients (Murphy 2015)
and other parameters.
THRESHOLD LEVEL OF SOIL ORGANIC
MATTER CONTENT IN ARABLE LANDS
It may be difficult to establish a quanti-
tative evidence for a critical threshold
(Körschens et al. 1998; Reynolds et
al. 2007; Gregory et al. 2015) of SOM
content for the diverse global soils and
growing conditions. Furthermore, the
range of an adequate level of SOM may
differ among soils, climates, management,
and farming systems. However, a value of
2% of SOC content (SOC is about 50% of
SOM) in the root zone has been suggested
for soils of temperate climates (Greenland
1975; Hamblin and Davies 1977; Johnston
1986; Loveland and Webb 2003; Oldfield
et al. 2019), and 1.1% for soils of the trop-
ics (Aune and Lal 1997). A few researchers
argue that the threshold level may be
less than 1% of SOC in some stable soils
(Šeremešic´ et al. 2011). Others opine that
it would be difficult to obtain the maxi-
mum crop yield in soil with SOC levels
of less than 1% (Kay and Angers 1999).
Therefore, the threshold SOC level may
be a soil/site-specific parameter, which
must be established and managed because
soil functionality can decline without an
adequate level of SOC content (Liu et al.
2005; Gregory et al. 2015).
The threshold level and response of
crop yield to SOM content also depend
on the type and degree of soil degradation
(figure 2). Rather than the simple process
of decline in soil physical properties and
Figure 2
Different types of soil degradation with adverse impacts on soil organic matter
(SOM) content.
Soil
degradation
• Climate change
• Decoupling of the
coupled cycling of
H
2
O, C, N, P, S
• Gaseous emissions
from soil
• Acidification
• Sodication/salinization
• Alkalization
• Elemental imbalance
• Pollution/contamination
• Toxicity
• Decline in aggregation
• Crusting/sealing
• Compaction
• Erosion/land slides
• Water imbalance
• Drought/flood
syndrome
• Unfavorable soil
temperatures
• Depletion of SOM content
• Destabilization of SOM in
the subsoil
• Methanogenesis
• Nitrification/denitrification
Biological
Chemical
Ecological
Physical
processes (i.e., aggregation, crusting, com-
paction, erosion, drought, and unfavorable
temperature and moisture regimes),
chemical characteristics (i.e., acidification,
alkalization, sodication, pollution, and ele-
mental toxicity), and biological parameters
(i.e., reduction in SOM content and turn-
over, in activity and species diversity of soil
biota, decline in microbial biomass C, and
reduction in ability of the soil to suppress
pests and pathogens), the cascading effect
of degradation may lead to destabiliza-
tion of SOM content even in the subsoil
(Rumpel and Kögel-Knabner 2011).
Figure 3 provides a conceptual basis of
crop yield response to changes in SOM
content in (1) depleted soil being restored,
and (2) soils with a high SOM content
being degraded. The graphic response
in figure 3a, with and without inputs of
amendment, indicates impact on yield
by the nutrient supply capacity of SOM
content. The graphic response in figure
3b indicates the importance of SOM on
PAWC and structural tilth effects. The
yield response levels off at the thresh-
old level that varies among soils: climate,
texture, and with/without input of amend-
ment (e.g., fertilizers or manure). Note the
threshold below which the yield decline
is lower with than without application of
amendments (figure 3a) and lower with
fine-textured than that in course-textured
soils (figure 3b).
In the scenario of soils with a high
antecedent SOC content and deplet-
ing, the threshold level below which
yield begins to decline is also lower with
than without amendment (figure 3c),
and lower in fine-textured than course-
textured soils (figure 3d). Thus, a critical
threshold can be highly soil/site specific
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JOURNAL OF SOIL AND WATER CONSERVATION
MARCH/APRIL 2020—VOL. 75, NO. 2
Figure 3
Hypothetical crop yield response curves to changing soil organic matter (SOM)
content. (a and b) Soils depleted of their SOM content and being restored: (a) yield
response with and without amendment, and (b) yield response of coarse textured
and heavy textured soils. (c and d) Soils with a high antecedent SOM content and
being depleted: (c) yield response with and without amendment and (d) yield
response of fine versus coarse textured soils.
Relative crop yield
Relative crop yield
Increasing soil organic matter content
Decreasing soil organic matter content
With amendment
Nutrient ef
fect
Without amendme
nt
Critical threshold
Critical threshold
Critical threshold
Critical threshold
Coarse texture
Fine texture
PA
WC and soil
tilth ef
fect
Low
High
High
Low
High
Low
High
Low
With amendment
Nutrient effect
Without amendme
nt
Critical threshold
Critical threshold
Critical threshold
Critical threshold
Coarse texture
Fine texture
PAWC soil
structure effect
(b)
(a)
(d)
(c)
and depends on a range of inherent and
managerial factors. Sustainable manage-
ment of SOM content also has benefits
toward saving/replacement of N and
other fertilizers (Schjønning et al. 2018;
Hijbeek et al. 2018), along with saving
of some irrigation water (Williams et al.
2016; Ankenbauer and Loheide II 2017).
CONCLUSIONS
Synthesis of the available literature shows
the following:
1. Increase in SOM content of depleted/
degraded soils can have a positive effect
on crop yield.
2. The critical/threshold level of SOC may
be about 2% in soils of the temperate
zone and ~1% for those of the tropics.
3. The positive yield response may be due
to increase in PAWC of coarse tex-
tured soils, and due to N availability at
low rates of N.
4. Input of nitrogenous fertilizers and
irrigation water can be saved by
increasing SOM content.
5. Fertilizer and irrigation can mask the
positive effects of SOM content.
Additional research is needed to establish
critical limits/ranges of SOM content for
diverse soils, climates, and ecoregions.
REFERENCES
Allison, F.E. 1973. Soil Organic Matter and Its Role
in Crop Production, Volume 3. 1st ed. Amsterdam:
Elsevier Science.
Ankenbauer, K.J., and S.P. Loheide II. 2017. The
effects of soil organic matter on soil water
retention and plant water use in a meadow of
the Sierra Nevada, CA. Hydrological Processes
31(4):891–901.
Arrieche-Luna, I.E., and M. Ruiz-Dager. 2010.
Influence of inorganic and organic fertiliza-
tion on microbial biomass carbon and maize
yield in two soils of contrasting pH. Agrociencia
(Montecillo) 44(3):249–260.
Aula, L., N. Macnack, P. Omara, J. Mullock, and W.
Raun. 2016. Effect of fertilizer nitrogen (N) on
soil organic carbon, total N, and soil pH in long-
term continuous winter wheat (
Triticum aestivum
L.). Communications in Soil Science and Plant
Analysis 47(7):863–874.
Aune, J.B., and R. Lal. 1997. Agricultural productivity
in the tropics and critical limits of properties of
Oxisols, Ultisols, and Alfisols. Tropical Agriculture
74(2):96–103.
Banwart, S., H. Black, Z. Cai, P. Gicheru, H. Joosten,
R. Victoria, E. Milne, E. Noellemeyer, and U.
Pascual. 2015. The global challenge for soil car-
bon.
In
Soil Carbon: Science, Management and
Policy for Multiple Benefits, eds. S.A. Banwart, E.
Noellemeyer, and E. Milne, 1–9. Wallingford: CABI.
Bauer, A., and A.L. Black. 1992. Organic carbon
effects on available water capacity of three soils
textural groups. Soil Science Society of America
Journal 56(1):248–254.
Baver, L.D. 1940. Soil Physics. New York: John Wiley
& Sons, Ltd.
Bouyoucos, G.J. 1939. Effect of organic matter on
the water holding capacity and the wilting points
of mineral soils. Soil Science 47(1939):377–383.
Bryant, L. 2015. Organic Matter Can Improve Your
Soil’s Water Holding Capacity. New York: Natural
Resources Defense Council. https://www.nrdc.
org/experts/lara-bryant/organic-matter-can-
improve-your-soils-water-holding-capacity.
Doran, J.W., and M.R. Zeiss. 2000. Soil health and
sustainability: Managing the biotic component of
soil quality. Applied Soil Ecology 15(1):3–11.
Dungait, J., C. Ghee, J. Rowan, B. McKenzie, C.
Hawes, E. Dixon, E. Paterson, and D. Hopkins.
2013. Microbial responses to the erosional
redistribution of soil organic carbon in arable
fields. Soil Biology and Biochemistry 60(May 1,
2013):165–201.
Feller, C., and M. Bernoux. 2008. Historical advances
in the study of global terrestrial soil organic
Relative crop yield
Relative crop yield
Page 6
31A
MARCH/APRIL 2020—VOL. 75, NO. 2
JOURNAL OF SOIL AND WATER CONSERVATION
carbon sequestration. Waste Management
28(4):734–740.
Feller, C., E. Blanchart, M. Bernoux, R. Lal, and R.
Manlay. 2012. Soil fertility concepts over the
past two centuries: The importance attributed
to soil organic matter in developed and devel-
oping countries. Archives of Agronomy and Soil
Science 58(1, SI):S3–S21.
Feustal, I.C., and H.G. Byers. 1936. The compara-
tive moisture-absorbing and moisture-retaining
capacities of peat and soil mixtures.
In
UDSA
Technical Bulletin 532, 1–25. Washington, DC:
United States Department of Agriculture.
Ghaley, B.B., H. Wösten, J.E. Olesen, K. Schelde,
S. Baby, Y.K. Karki, C.D. Børgesen, P. Smith, J.
Yeluripati, R. Ferrise, M. Bindi, P. Kuikman, J.-P.
Lesschen, and J.R. Porter. 2018. Simulation of
soil organic carbon effects on long-term winter
wheat (
Triticum aestivum
) production under vary-
ing fertilizer inputs. Frontiers in Plant Science
9(2018):1158.
Greenland, D.J. 1975. Bringing the Green
Revolution to the shifting cultivator. Science
190(4217):841–844.
Gregory, A.S., K. Ritz, S.P. McGrath, J.N. Quinton,
K.W.T. Goulding, R.J.A. Jones, J.A. Harris, R.
Bol, P. Wallace, E.S. Pilgrim, and A.P. Whitmore.
2015. A review of the impacts of degradation
threats on soil properties in the UK. Soil Use and
Management 31(S1):1–15.
Gregory, A., C. Watts, B. Griffiths, P. Hallett, H. Kuan,
and A. Whitmore. 2009. The effect of long-term
soil management on the physical and biologi-
cal resilience of a range of arable and grassland
soils in England. Geoderma 153(October 1,
2009):172–185.
Griffiths, B., P. Hallett, H. Kuan, Y. Pitkin, and M.
Aitken. 2005. Biological and physical resilience
of soil amended with heavy metal-contami-
nated sludge. European Journal of Soil Science
56(2005):197–206.
Hamblin, A.P., and D.B. Davies. 1977. Influence of
organic matter on the physical properties of some
East Anglian soils of high silt content. Journal of
Soil Science 28(1):11–22.
Hijbeek, R., M.K. Ittersum, H. Berge, and A.
Whitmore. 2018. Evidence review indicates
a re-think on the impact of organic inputs
and soil organic matter on crop yield.
In
2018
IFS Agronomic Conference. Cambridge, UK:
International Fertiliser Society.
Hijbeek, R., M.K. van Ittersum, H.F.M. ten Berge,
G. Gort, H. Spiegel, and A.P. Whitmore. 2017.
Do organic inputs matter – A meta-analysis of
additional yield effects for arable crops in Europe.
Plant and Soil 411(1):293–303.
Hudson, B.D. 1994. Soil organic matter and avail-
able water capacity. Journal of Soil and Water
Conservation 49(2):189–194.
Janzen, H.H. 2006. The soil carbon dilemma: Shall we
hoard it or use it? Soil Biology and Biochemistry
38(3):419–424.
Johnston, A.E. 1986. Soil organic matter, effects
on soils and crops. Soil Use and Management
2(3):97–105.
Johnston, A., P. Poulton, and K. Coleman. 2008.
Chapter 1. Soil organic matter: Its importance
in sustainable agriculture and carbon dioxide
fluxes. Advances in Agronomy 101(November
30, 2008):1–57.
Kay, B.D., and D.A. Angers. 1999. Soil Structure.
In
Handbook of Soil Science, ed. M.E. Sumner,
229–276. Boca Raton, FL: CRC Press.
Kemper, W.D., and E.J. Koch. 1966. Aggregate Stability
of Soils from Western United States and Canada.
In
USDA Technical Bulletin 171386. Washington,
DC: USDA Economic Research Service.
Körschens, M., A. Weigel, and E. Schulz. 1998.
Turnover of soil organic matter (SOM) and
long-term balances — tools for evaluating
sustainable productivity of soils. Zeitschrift
für Pflanzenernährung und Bodenkunde
161(4):409–424.
Lal, R. 2016. Soil health and carbon management.
Food and Energy Security 5(4):212–222.
Lal, R., R. Horn, and T. Kosaki. 2018a. Soil and
Sustainable Development Goals. Stuttgart:
Catena-Scheizerbart.
Lal, R., P. Smith, H.F. Jungkunst, W.J. Mitsch, J.
Lehmann, P.K.R. Nair, A.B. McBratney, J.C.
de Moraes Sa, J. Schneider, Y.L. Zinn, A.L.A.
Skorupa, H.-L. Zhang, B. Minasny, C. Srinivasrao,
and N.H. Ravindranath. 2018b. The carbon
sequestration potential of terrestrial ecosys-
tems. Journal of Soil and Water Conservation
73(6):145A–152A, doi:10.2489/jswc.73.6.145A.
Liu, C.-A., and L.-M. Zhou. 2017. Soil organic
carbon sequestration and fertility response to
newly-built terraces with organic manure and
mineral fertilizer in a semi-arid environment. Soil
and Tillage Research 172(2017):39–47.
Liu, X., S. Herbert, A. Hashemi, X. Zhang, and G.
Ding. 2005. Effects of agricultural management
on soil organic matter and carbon transforma-
tion - A review. Plant, Soil and Environment
56(12):531–543.
Loveland, P., and J. Webb. 2003. Is there a critical
level of organic matter in the agricultural soils
of temperate regions: A review. Soil and Tillage
Research 70(1):1–18.
Manlay, R.J., C. Feller, and M.J. Swift. 2007.
Historical evolution of soil organic matter con-
cepts and their relationships with the fertility and
sustainability of cropping systems. Agriculture,
Ecosystems & Environment 119(3):217–233.
Menšík, L., L. Hlisnikovsky, and E. Kunzová. 2019.
The state of the soil organic matter and nutrients
in the long-term field experiments with applica-
tion of organic and mineral fertilizers in different
soil-climate conditions in the view of expecting
climate change.
In
Organic Fertilizers: History,
Production and Applications, eds. M. Larramendy
and S. Soloneski, 1–29. London: IntechOpen.
Minasny, B., and A.B. McBratney. 2018. Limited effect
of organic matter on soil available water capacity.
European Journal of Soil Science 69(1):39–47.
Murphy, B.W. 2015. Impact of soil organic matter
on soil properties—a review with emphasis on
Australian soils. Soil Research 53(6):605–635.
Oelofse, M., B. Markussen, L. Knudsen, K. Schelde,
J. Olesen, L. Jensen, and S. Bruun. 2015. Do soil
organic carbon levels affect potential yields and
nitrogen use efficiency? An analysis of winter
wheat and spring barley field trials. European
Journal of Agronomy 66(May 1, 2015):62–73.
Oldfield, E., M. Bradford, and S. Wood. 2019. Global
meta-analysis of the relationship between soil
organic matter and crop yields. Soil 5(January 15,
2019):15–32.
Paul, E.A. 2016. The nature and dynamics of soil
organic matter: Plant inputs, microbial transfor-
mations, and organic matter stabilization. Soil
Biology and Biochemistry 98(2016):109–126.
Petersen, G.W., R.L. Cunningham, and R.P. Matelski.
1968. Moisture characteristics of Pennsylvania
soils: II. Soil factors affecting moisture retention
within a textural class—silt loam. Soil Science
Society of America Journal 32(1968):866–870.
Ramos, F.T., E.F.G. de C. Dores, O.L. dos S. Weber,
D.C. Beber, J.H. Campelo Jr., and J.C. de S. Maia.
2018. Soil organic matter doubles the cation
exchange capacity of tropical soil under no-till
farming in Brazil. Journal of the Science of Food
and Agriculture 98(9):3595–3602.
Reeves, D.W. 1997. The role of soil organic matter in
maintaining soil quality in continuous cropping
systems. Soil and Tillage Research 43(1):131–167.
Reynolds, D., C. Drury, X. Yang, C.A. Fox, C. Tan,
and T.Q. Zhang. 2007. Land management effects
on the near-surface physical quality of a clay
loam soil. Soil and Tillage Research (October 1,
2007):316–330.
Rumpel, C., and I. Kögel-Knabner. 2011. Deep soil
organic matter—A key but poorly understood
component of terrestrial C cycle. Plant and Soil
338(1):143–158.
Page 7
32A
JOURNAL OF SOIL AND WATER CONSERVATION
MARCH/APRIL 2020—VOL. 75, NO. 2
Salter, P.J., and F. Haworth. 1961. The available-water
capacity of a sandy loam soil. Journal of Soil
Science 12(2):326–334.
Salter, P.J., and J.B. Williams. 1963. The effect of
farmyard manure on the moisture characteris-
tic of a sandy loam soil. Journal of Soil Science
14(1):73–81.
Schjønning, P., J.L. Jensen, S. Bruun, L. Jensen, B.
Christensen, L. Munkholm, M. Oelofse, S. Baby,
and L. Knudsen. 2018. The role of soil organic
matter for maintaining crop yields: Evidence for a
renewed conceptual basis. Advances in Agronomy
150(January 1, 2018):35–79.
Šeremešic´, S., M.D,I. Ðalovic´, T. Zeremski, and J.
Ninkov. 2011. Management of soil organic
carbon in maintaining soil productivity and
yield stability of winter wheat. Plant Soil and
Environment 57(5):201–206.
Six, J., S.D. Frey, R.K. Thiet, and K.M. Batten. 2006.
Bacterial and fungal contributions to carbon
sequestration in agroecosystems. Soil Science
Society of America Journal 70(2):555–569.
Wei, W., Y. Yan, J. Cao, P. Christie, F. Zhang, and M.
Fan. 2016. Effects of combined application of
organic amendments and fertilizers on crop yield
and soil organic matter: An integrated analysis of
long-term experiments. Agriculture, Ecosystems
& Environment 225(2016):86–92.
Williams, A., M.C. Hunter, M. Kammerer, D.A. Kane,
N.R. Jordan, D.A. Mortensen, R.G. Smith, S.
Snapp, and A.S. Davis. 2016. Soil water holding
capacity mitigates downside risk and volatility in
US rainfed maize: Time to invest in soil organic
matter? PLOS ONE 11(8):e0160974.
Wood, S.A., N. Sokol, C.W. Bell, M.A. Bradford, S.
Naeem, M.D. Wallenstein, and C.A. Palm. 2016.
Opposing effects of different soil organic matter
fractions on crop yields. Ecological Applications
26(7):2072–2085.