Agriculture Reference
In-Depth Information
Figure 5.3
. Change in soil organic carbon (C) and nitrogen (N) following afforestation of
previously cropped Oshtemo/Kalamazoo loam soils at the Kellogg Forest, two tree planta-
tions in the MCSE, and the Russ Forest in nearby Cass County, Michigan. From S. Morris
(unpublished data).
Table 5.4. A comparison of SOC, total nitrogen (N), and C:N mass ratio of soils
from the MCSE Conventional system and six privately owned sites in Cass
County, Michigan.
a
Site
Number of
Samples
Profile SOC (Mg ha
−1
)
Profile N (Mg ha
−1
)
C:N Ratio
MCSE
6
59.1 (7.3)
bc
8.7 (0.71)
c
6.73 (0.24)
a
Field 1
5
37.6 (3.6)
a
4.1 (0.4)
a
9.1 (0.09)
bc
Field 2
5
63.4 (5.0)
ac
6.0 (0.6)
a
10.6 (0.26)
c
Field 3
5
59.7 (9.9)
bc
5.0 (0.7)
ab
11.9 (0.66)
c
Field 4
5
44.0 (1.7)
ab
4.6 (0.2)
a
9.7 (0.43)
b
Field 5
5
46.6 (4.6)
ab
5.0 (0.4)
ab
9.4 (0.84)
b
Field 6
5
73.7 (2.8)
c
7.1 (0.8)
bc
10.7 (0.78)
c
a
Samples to a soil profile depth of 1 m, corrected for equivalent weights. See Table 5.1 for a description of the MCSE
Conventional system. Field sites 1-6 on the same soil type, under conventional till corn-soybean rotation. Data are
means (±SE); means followed by similar letters do not differ significantly at
α
= 0.05.
Source:
Morris et al. (2007).
land was first cleared, and thus less capacity to accumulate N. Total N content is
somewhat higher in KBS soils than on local commercial farms with similar soil C
contents (Table 5.4), resulting in a lower C:N ratio for the KBS soils in this com-
parison. These data further demonstrate the capacity for these soils to accrue C and
N during afforestation in most cases, depending on tree species composition and
SOM content. That C accrued in these soils indicates that they have not reached C
saturation—the concept that a particular soil under a specific set of controls (such
as the level of aggregation) can only sequester a specific amount of C. Soil C satu-
ration been observed in both agricultural and forested soils (Six et al. 2002a, b).
