Takata, Y, Funakawa, S, Akshalov, K, Ishida, N, Kosaki, T (2008). Regional evaluation of the spatio-temporal variation in soil organic carbon dynamics for rainfed cereal farming in northern Kazakhstan. SOIL SCIENCE AND PLANT NUTRITION, 54(5), 794-806.
A regional evaluation of the soil organic carbon (SOC) dynamics for the chernozem zone in northern Kazakhstan is now vitally important for agricultural and environmental policy making. The objectives of the present study were: (1) to predict spatial and temporal variability in C input as crop residues using multi-temporal MODIS satellite images, (2) to clarify spatial and temporal variability in CO2 emission as SOC output using geostatistics and model equations, (3) to clarify spatial and temporal variability in the SOC budget using the results from (1) and (2). The mean growing-season C input as plant residues in cereal fields ranged from 0.9 to 1.4 Mg C ha(-1), with higher values in wet years. Carbon input as plant residues was higher in the northern part of the area than in the other parts. The average growing-season CO2 emission ranged from 0.9 to 1.1 Mg C ha(-1), and was also higher in wet years than in dry years. In addition, more CO2 was emitted in the northern part of this area. Accordingly the average growing-season C budget ranged from -0.2 to 0.3 Mg C ha(-1) and showed a negative correlation with air temperature during the crop-growing season. The 5-year C budget for different crop rotation systems ranged from -1.0 (3-year cropped cereal with 2-year bare fallow) to 0.4 (5-year continuous cereal cropped) Mg C ha(-1). These results indicate that fallow-based crop rotation systems are degradative with regard to the SOC budget in the studied area.