Soil organic carbon changes in particle-size fractions following cultivation of Black soils in China |
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| Authors: | Aizhen Liang Xueming Yang Xiaoping Zhang Neil McLaughlin Yan Shen Wenfeng Li |
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| Institution: | aNortheast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130012, China;bGreenhouse and Processing Crops Research Centre, Agriculture and Agri-Food Canada, Harrow N0R1G0, Canada;cEastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, Ottawa K1A0C6, Canada |
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| Abstract: | Soil texture can be an important control on soil organic carbon (SOC) retention and dynamics. The (clay + silt)-sized SOC pool (SOC < 20 μm) in non-cultivated or grassland soils has been proposed to reach an equilibrium or maximum level named protective capacity. Proper knowledge of SOC in this size fraction in non-cultivated and cultivated Black soils is important to evaluate management-induced changes in SOC in NE China. Twenty-seven paired soil samples (non-cultivated vs. cultivated) were collected in the Black soil zone in Heilongjiang and Jilin provinces. Bulk soil was dispersed in water with an ultrasonic probe and then soil size fractions were collected using the pipette technique for SOC analyses. Soil organic carbon in bulk soil and size fractions was measured by dry combustion. Average content of SOC < 20 μm was 23.2 g C kg−1 at the 0–30 cm depth for the non-cultivated soils, accounting for 75.1% of the total SOC at the same depth. There was significant positive relationship between soil clay plus silt content and SOC < 20 μm in non-cultivated soils. Accordingly, a model of the maximum SOC < 20 μm in 0–30 cm depth of non-cultivated Black soils was developed: y = 0.36x where y is the maximum SOC < 20 μm pool (g C kg−1) and x is the percentage of clay + silt (<20 μm) content. The average content of SOC < 20 μm was 18.7 g C kg−1 at 0–30 cm depth for cultivated soils, accounting for 81.5% of total SOC. This average value of SOC was 4.4 g C kg−1 less than the maximum value (23.1 g C kg−1) and accounted for 55.0% of the difference of SOC between non-cultivated and cultivated Black soils. Cultivation resulted in 45.0% loss of sand-sized (>20 μm) SOC concentration relative to SOC < 20 μm. This result indicates that SOC < 20 μm and sand-sized SOC both play important roles in SOC dynamics resulting from management practices. This model can be applied to calculate the actual potential to restore SOC for cultivated Black soils under conservation tillage in NE China. |
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| Keywords: | China Black soils Organic carbon Restoring potential Soil texture |
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