Soil organic matter dynamics under grain farming in Northern Kazakhstan
Soil organic matter dynamics under grain farming in Northern Kazakhstan
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DOI：
10.1080/00380768.2004.10408596
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发表时间：
2004-02
影响因子：
2
通讯作者：
Shinya Funakawa;Iwao Nakamura;K. Akshalov;T. Kosaki
中科院分区：
文献类型：
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作者：
Shinya Funakawa;Iwao Nakamura;K. Akshalov;T. Kosaki
由于其能够储存大量的土壤有机质（SOM），从农业和环境的角度来看，盐渍土是最重要的资源之一。通过对土壤呼吸和土壤环境因子（如土壤温度和含水量）的原位分析，确定了哈萨克斯坦北方盐渍化土壤在粮食种植条件下的有机质收支。在哈萨克斯坦北方Shortandy的Barayev Kazakh谷物农业研究和生产中心的实验农场建立了5个试验区，包括1个休闲地（年平均降水量和年平均气温分别为323 mm和1.6°C）。4月上旬土壤日平均温度上升到0 °C以上，6月中旬至8月中旬保持在20°C以上，9月底急剧下降到5°C以下。大多数生物活动被认为在4月至9月是有限的。另一方面，土壤水分含量保持较高的解冻后，直到6月中旬，然后持续下降，除了在降雨事件的作物地块。土壤呼吸速率在6月下旬至7月上旬达到最大值，其波动规律与土壤温度相似，而土壤微生物碳、氮含量的波动规律与土壤含水量相似。为了用土壤环境因子来表示土壤呼吸速率，引入了以下关系式作为模型函数：Cem = aM pbexp（-E/RT）。利用实测数据Cem（土壤日呼吸速率）、M（土壤体积含水量）和T（土壤绝对温度），通过对数变换后的逐步多元回归确定了系数a、B和E（阿克里尼乌斯方程中的活化能）。结果表明，土壤呼吸速率与活化能E之间存在显著的相关关系，而土壤含水量对土壤呼吸速率的贡献不确定。利用回归方程和土壤温度、水分监测数据，计算出整个种植期的土壤呼吸累积量为2.5 ~ 3.2MgChap ~（-1）。预计将被纳入土壤的作物残茬量在1.6至4.4 Mg C hap之间。1除了种植燕麦的地块（残留量高于小麦）外，今年土壤收支略有负值，即土壤失去了有机质储量。虽然它是很难概括的C收支在不同年份，因为作物生长的变化很大，由于波动的水资源，夏季休耕（无残留物）的缺点是显而易见的SOM预算。休闲地土壤净呼吸速率为2.9 Mg C hap-1，约相当于耕层（30 cm）土壤有机质总储量的4%（70 ~ 80 Mg C hap-1）。为了减少土壤有机质的进一步损失，应重新考虑至少均匀广泛地利用夏季休闲地。
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 1.6°C, respectively). Mean daily soil temperature increased to above O°C in early April, remaining at above 20°C from mid-June to mid-August, and then sharply decreased to below 5°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 pbexp(-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 hap-1 On the other hand, the amounts of crop residues in the cropped plots that were expected to be incorporated into the soils ranged from 1.6 to 4.4 Mg C hap-1 Except for the plot planted with oats (higher amounts of residues than for wheat), the SOIL budget was slightly negative in this year, that is, the soils lost their organic matter stock. Although it is difficult to generalize the C budget in different years because of the large variations in crop growth due to fluctuating water resources, the disadvantage of summer fallow (no residues) was obvious in terms of SOM budget. The net soil respiration rate in the fallow plot, 2.9 Mg C hap-1 was approximately equivalent to 4% of the total SOM stock in the plow layer (30 cm) (70 to 80 Mg C hap-1 To reduce further loss of SOM, at least evenly extensive use of summer fallow should be reconsidered.