Regional evaluation of the spatio-temporal variation in soil organic carbon dynamics for rainfed cereal farming in northern Kazakhstan

Abstract

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 s, (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.

Analysis of Spatial and Temporal Variation of Soil Organic Carbon Budget in Northern Kazakhstan

“…From the agricultural and environmental viewpoints, summer fallow should be eliminated from the crop rotation system in northern Kazakhstan. 17 ).…”

“…The EVI data could detect the phenological difference among cereal, fallow and perennial grass 17 . Using the EVI data, all ground-checked meadow fields (about 5,000 ha at the SC site) and fallow fields (about 4,000 ha at the SC site) for each year were extracted 17 . Annual carbon input as plant residues was estimated using MODIS satellite images.…”

“…Annual CO 2 emission was estimated using the predicted equation (Table 2). The procedures are described in Takata et al 17 in detail. The annual carbon budget of all fields was then calculated by subtracting annual CO 2 emission from annual carbon input.…”

“…Upper figure is annual carbon input as plant residues, middle is annual CO 2 emission, and lower is annual SOC budget (Source: Takata et al 17 ).…”

“…Takata et al 17 assessed the effect of crop rotation system and climatic condition on the spatial and temporal variation of CO 2 emission, carbon input as plant residues, and SOC budget at a regional scale in northern Kazakhstan, using satellite images, a geostatistical approach, and simulation models of CO 2 emission.…”