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| Characteristics of Organic Carbon Stabilization in Paddy Soil Under Long-term Different Fertilization |
| Received:November 26, 2014 |
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| KeyWord:soil organic carbon;fractionation;stabilization mechanism;paddy soil;carbon sequestration |
| Author Name | Affiliation | E-mail | | XU Xiang-ru | College of Land and Environment, Shenyang Agricultural University, Shenyang 110161, China
Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China | | | CAI An-dong | Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China | | | XU Ming-gang | Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China | | | WANG Jing-kuan | College of Land and Environment, Shenyang Agricultural University, Shenyang 110161, China | j-kwang@163.com | | ZHANG Wen-ju | Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China | zhangwenju01@caas.cn |
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| Abstract: |
| Understanding the mechanisms of soil organic carbon(SOC) stabilization would help improve soil carbon sequestration in paddy soil. In this paper, we obtained paddy soils from a 30 year experimental field under five different fertilization, including no fertilizer(control), mineral nitrogen(N)-phosphorus(P)-potassium(K) fertilizers(NPK), 70% mineral N+30% organic N plus PK(NPKM7/3), 50% mineral N+50% organic N plus PK(NPKM5/5), and 30% mineral N+70% organic N plus PK(NPKM3/7). Organic N was provided from green manure and pig manure. The soils were subjected to separating unprotected, and physically, chemically, bio-chemically, physical-chemically, and physical-biochemically protected SOC fractions by a physical-chemical combined fractionation method. Except the unprotected light fraction and the occluded silt and clay-sized fraction, the mass proportion of all other SOC factions was significantly different between the treatments. Compared with non-fertilization(CK) treatment, chemical fertilizers mixed with organic manure(NPKM7/3、NPKM5/5 and NPKM3/7) significantly increased the content of total SOC(19.1~25.0 g·kg-1), unprotected coarse particulate organic carbon(cPOM)(8.41~12.7 g·kg-1), and physically protected aggregate(μagg) organic carbon(6.41~6.62 g·kg-1) in red paddy soil(P<0.05). There were no significant differences for the chemically, biochemically, physical-chemically and physical-biochemically protected fractions between the five treatments. These results indicated that the unprotected cPOM and the physically protected μagg fractions were the most sensitive ones in long-term fertilization. There was a linear positive correlation between total SOC and tcPOM, physically protected μagg, and occluded POM inside the μagg(iPOM) fraction(P<0.05), and their response efficiency to total SOC accumulation(the slope of the regression)was 0.5, 0.12, and 0.12 respectively. However, the response efficiency of non-hydrolysis clay and physic-chemically protected silt fraction to total SOC accumulation was only 0.02 to 0.03, even though they had significant responses. There was no significant relationship of the rest fractions with total SOC. Under the present cropping and management practices, cPOM and micro-aggregates were the main stabilization mechanisms for soil carbon sequestration. Soil physically, chemically, biological-chemically and physical-biochemically protected SOC fractions might have reached the maximum capacity in this paddy soil. |
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