Managing Soil Organic Carbon Concentration by Cropping Systems and Fertilizers in the North China Plain - Principles of Sustainable Soil Management in Agroecosystems - page 192

Soil samples were collected at 79 sites in the Quzhou County in May 1980 and
again at the same sites in May 1999 before the wheat harvest. At each site, 3-5 kg
of sample of 0- to 20-cm depth was collected for laboratory analysis. Sampling sites
were identified via Global Positioning System (GPS) at the same location and time
of year in 2006. The distribution of sample sites for SOC concentration analysis was
based on the Second National Soil Survey of China (SNSS) map (1:50,000), shown
in Figure 8.2.
Soil samples obtained in 2006 were then transferred into 20 × 15 cm plastic bags
and labeled with the soil sample number, the farmers' names and addresses, and
the date of collection. After cleaning off the plant residues, removing stones and
other debris, samples were air dried. Then each soil sample was divided into four
equal parts, from which two nonadjacent samples were retained and the remaining
two were stored. This process was repeated until the two nonadjacent samples were
reduced to approximately 0.5 kg. The final soil samples were gently ground and
sieved through 0.15-mm sieves prior to C analysis.

Henantan

Sitan

Quzhou

Huaiqiao

Baizhai

Liyue

Dahedao

Houcun

Anzhai

Yizhuang

FIGURE 8.2 Location of soil sampling in Quzhou County, Hebei Province.