Managing Soil Organic Carbon Concentration by Cropping Systems and Fertilizers in the North China Plain - Principles of Sustainable Soil Management in Agroecosystems - page 193

8.2.3 d AtA A nAlySiS
Soil organic matter concentration was analyzed using the rapid dichromate oxida-
tion method (Tiessen and Mioir 1993) and later converted to SOC using a factor of
0.58 (Post et al. 1982). Of these, 67 samples were selected for further analysis after
checking all the data.
Changes in SOC concentrations were analyzed using the paired samples t-test
using SPSS 11.5 for Windows. First, the results from the entire sampling area
obtained in 1980 and 1999 were analyzed via contrast analysis using the year as a
variable. Then the results obtained between 1999 and 2006 were similarly tested.
Second, the data were analyzed based on the different cropping systems used during
1999 and 2006. Third, the effects of the SOC concentration were evaluated by com-
paring the data for changes in the cropping system from 1999 to 2006.

8.3 RESULTS AND DISCUSSIONS

8.3.1 C hAnge in SoC C onCentrAtion from 1980 to 1999
The results show that the SOC concentration was significantly different between sam-
ples obtained in 1980 and 1999 (Tables 8.2 and 8.3). The minimum and maximum

TABLE 8.2
Variation of SOC Concentrations in 67 Samples Obtained from Quzhou in
1980, 1999, and 2006

SOC Concentration (g kg -1 )

Year Minimum Maximum Average SD C.V. (%)

1980 2.84 7.59 5.01 1.82 36

1999 3.39 11.48 6.93 2.7 39

2006 2.73 11.12 6.79 3.06 45

TABLE 8.3
SOC Concentration in Quzhou between 1980-1999 and 1999-2006

95% Confidence
Interval of the
Difference

Period of
Assessment
of SOC

Paired
Differences
Mean (g kg -1 )

Standard
Error
Mean

Standard
Deviation

Signification
(Two-Tailed) df

t

Low Upper

1980-1999 -1.92 1.42 0.17 -2.26 -1.57 -11.01 6 0.00*

1999-2006 0.15 2.29 0.28 -0.41 0.70 0.52 6 0.60**

* P < 0.01; ** P > 0.05.