Organic Matter and Sustainability - Sustainable Management of Soil Organic Matter - page 29

Table 1.2.3. C org content (g kg − 1 ) and CEC (mmol c kg − 1 ) of the different plots.

Bad Lauchstädt Müncheberg Groß Kreutz

Fertilizer C org a CEC C org CEC C org CEC

Control 16.6 209.6 4.3 32.5 4.2 33.9

N 19.3 208.7 4.69 32.0 5.2 36.4

FYM 24.1 219.4 4.63 31.5 5.5 40.0

FYM + N 27.0 223.8 4.9 35.6 6.8 46.2

a M. Körschens, Bad Lauchstädt, 1999, personal communication.
The analytical error was ± 0.5 g kg − 1 for C org and ± 5 mmol c kg − 1 for CEC.

content (Table 1.2.3). According to Stevenson (1982), the ability of SOM
to form organomineral complexes increases with the clay content. These
complexes protect the organic material against mineralization resulting
in higher C org contents. Therefore, the C org content of the studied soils
corresponds to the fertilizer application rate as well as the clay content.
For the sandy soil at Müncheberg, the fertilizer regime had no significant
effect on C org content. This may be as a result of the relatively low fertilizer
application rate at this site (Table 1.2.2).
The CEC values of the loamy soil are 5-6 times higher than those of the
sandy soils. This is due to the higher clay and organic carbon content of
the loamy soil (Tables 1.2.1 and 1.2.3) because CEC depends on clay
and SOM content. The CEC for the loamy soil samples increases in the
sequence: control < N < FYM < FYM + N. For the sandy soil from Groß
Kreutz, the CEC increases in the same sequence, but the differences in
CEC due to the type of fertilization are most distinct for the samples from
the loamy soil. This finding is also correlated with the differences in C org
content.
Figure 1.2.1 shows the FT-IR spectra of the hot water extracts of
the soils from the studied long-term field experiments. The spectra are
normalized on the C-O-C band at 1000 cm −1 , which shows the same
absorption intensity for all samples. All spectra show an overall scheme, but
there are differences in the absorption intensity especially of the C = O
band at 1710 and 1690 cm −1 , and the O-H band at 3500 cm −1 . As Celi
et al . (1998) show that the absorption intensity of the C = O group
correlates with the CEC of the samples, we focus the discussion on this
absorption band. A comparison of the FT-IR spectra of the hot water
extracts of the soil samples from the loamy soil experiment (Fig. 1.2.1)
show that the intensity of the C = O bands (representing carboxyl groups)
decreases in the sequence: FYM + N > FYM > N > control. For the
samples from the sandy soils with different fertilizer application rates,
the sequence was FYM > FYM +N>N>control.