Soil organic matter dynamics under grain farming in northern Kazakhstan

• Published in: Soil science and plant nutrition (Tokyo) 2004-12, Vol.50 (8), p.1211-1218
• Main Authors: Funakawa, S. (Kyoto Univ. (Japan)), Nakamura, I, Akshalov, K, Kosaki, T
• Format: Article
• Language: English
• Subjects: GRAIN CROPS; grain farming; KAZAKHSTAN; northern Kazakhstan; SOIL ORGANIC MATTER; SOIL RESPIRATION; SOM budget; summer fallow
• ISSN: 0038-0768; 1747-0765
• DOI: 10.1080/00380768.2004.10408596

Because of their ability to store a high amount of soil organic matter (SOM), Chernozem soils are one of the most important resources from both agricultural and environmental viewpoints. This study was carried out to determine the SOM budget under grain farming in the Chernozem soil of northern Kazakhstan through the analysis of in situ soil respiration and soil environmental factors such as soil temperature as well as moisture content. Five experimental plots including one fallow field were established at the experimental farm of Barayev Kazakh Research and Production Center of Grain Farming, Shortandy, northern Kazakhstan (mean annual precipitation and average year temperature are 323 mm and l.6 deg C, respectively). Mean daily soil temperature increased to above 0 deg C in early April, remaining at above 20 deg C from mid-June to mid-August, and then sharply decreased to below 5 deg C at the end of September. Most of the biological activities were considered to be limited from April to September. On the other hand, the soil moisture content remained high after thawing until mid-June and then continuously decreased in the cropped plots except during the rainfall events. The soil respiration rate recorded the highest values from late June to early July and overall fluctuations were similar to those of the soil temperature, unlike the fluctuations of soil microbial C and N contents, which exhibited similar patterns to those of the soil moisture content. In order to represent the daily soil respiration rates using the soil environmental factors, the following relationship was introduced as a model function: Cem = aM**b exp(-E/RT). The coefficients, a, b, and E (activation energy in Arrhenius equation), were determined by stepwise multiple regression after logarithm transformation using the measured data, Cem (daily soil respiration rate), M (volumetric soil moisture content), and T (absolute soil temperature). As a result, a significant relationship was always obtained between the soil respiration rate and the activation energy E, while the contribution of the soil moisture content to the soil respiration rate was uncertain. Using the regression equations and monitored data of soil temperature and moisture content, cumulative soil respiration throughout the cropping period was calculated to be in the range of 2.5 to 3.2 Mg C ha sup(-1). On the other hand, the amounts of crop residues in the cropped plots that were expected to be incorporated into the soils