Agriculture Reference
In-Depth Information
animals consuming plants create bioactive proteins, and exposure of plant and ani-
mal residues to soil microorganisms and various environmental conditions creates
humified soil organic matter complexes. Human intervention often results in harvest
of enormous quantities of carbon as food and energy products. Unintended con-
sequences of management can result in significant erosion of soil and leaching of
nutrients.
Across a number of studies in different states throughout the southeastern United
States, SOC was greater under grasslands than under croplands (Table 4.3). The
average difference in SOC between grassland and cropland was 16.3 Mg C ha
−1
.
SOC under grasslands was not different from that under forest. Many of these sur-
veys had single-field estimates of SOC and limited information on the type of man-
agement employed, yet pooling the data revealed reasonable conclusions about land
use effects on SOC. In a like manner from a survey of soil profiles (ultisols) through-
out Georgia in the southeastern United States, SOC stock to a depth of 30 cm was
similar between grassland (52.5 Mg C ha
−1
) and forestland (48.3 Mg C ha
−1
), both
of which were greater than under cropland (39.9 Mg C ha
−1
) (Franzluebbers 2010).
TABLE 4.3
Soil Organic C Stocks in Different Land Uses in the Southeastern
United States
Carbon Stock (Mg C ha
−1
)
Depth
(cm)
Study
Forest
Grass
Crop
Pr > F
Eastern Texas
a,b
30
N.D.
88 ± 18
57 ± 8
<0.01
Ten southeastern states
c
25
31 ± 12
31 ± 16
23 ± 15
0.04
Maryland
d
15
N.D.
32 ± 10
20 ± 7
0.01
Alabama
e,f
25 ± 6
60 ± 21
48 ± 26
34 ± 8
0.03
Mississippi, Georgia
g,h
25 ± 7
47 ± 2
38
22 ± 6
0.08
Mean
24 ± 6
49.9 z
47.4 z
31.1 y
Source:
Summarized from Franzluebbers, A.J.,
Soil Tillage Res.
, 83, 120, 2005.
Note:
z and y are mean separation notations, respectively.
a
Laws, W.D., and D.D. Evans,
Soil Sci. Soc. Am. Proc
. 13, 15, 1949.
b
Potter, K.N., H.A. Torbert, H.B. Johnson, and C.R. Tischler,
Soil Sci
., 164, 718, 1999.
c
McCracken, R.J. 1959. Certain properties of selected southeastern United States soils and mineralogi-
cal procedures for their study.
Southern Regional Bull
. 61. Virginia Agric. Expt. Sta., Virginia
Polytechnic Inst., Blacksburg, VA, 146 pp.
d
Islam, K.R., and R.R. Weil,
J. Soil Water Conserv
., 55, 69, 2000.
e
Fesha, I.G., J.N. Shaw, D.W. Reeves, C.W. Wood, Y. Feng, M.L. Norfleet et al. 2002. Land use effects
on soil quality parameters for identical soil taxa. pp. 233-238. In E. van Santen (Ed.),
Making Conservation
Tillage Conventional: Building a Future on 25 Years of Research
, Special Report No. 1, Alabama
Agricultural Experiment Station, Auburn University, Auburn, AL.
f
Torbert, H.A., S.A. Prior, and G.B. Runion,
J. Soil Water Conserv
., 59, 1, 2004.
g
Rhoton, F.E., and D.D. Tyler,
Soil Sci. Soc. Am. J
.,
54, 223, 1990.
h
Franzluebbers, A.J., J.A. Stuedemann, H.H. Schomberg, and S.R. Wilkinson,
Soil Biol. Biochem
.,
32,
469, 2000.
