作者机构：
[张文菊] Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences/National Engineering Laboratory for Improving Quality of Arable Land, Beijing, 100081, China;[张杨珠] College of Resources and Environment, Hunan Agricultural University, Changsha, 410128, China;Red Soil Experimental Station of Chinese Academy of Agricultural Sciences in Hengyang/National Observation and Research Station of Farmland Ecosystem in Qiyang, Qiyang, Hunan 426182, China;[高菊生; 刘淑军] Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences/National Engineering Laboratory for Improving Quality of Arable Land, Beijing, 100081, China, Red Soil Experimental Station of Chinese Academy of Agricultural Sciences in Hengyang/National Observation and Research Station of Farmland Ecosystem in Qiyang, Qiyang, Hunan 426182, China;[黄晶] Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences/National Engineering Laboratory for Improving Quality of Arable Land, Beijing, 100081, China, College of Resources and Environment, Hunan Agricultural University, Changsha, 410128, China, Red Soil Experimental Station of Chinese Academy of Agricultural Sciences in Hengyang/National Observation and Research Station of Farmland Ecosystem in Qiyang, Qiyang, Hunan 426182, China
通讯机构：
[Gao, J.-S.] I;Institute of Agricultural Resources and Regional Planning, China
关键词：
长期施肥;红壤性水稻土;土壤有机碳含量;土壤有机碳储量
摘要：
研究了1982—2012年长期不同施肥下红壤性水稻土土壤有机碳含量变化、固碳趋势及外源碳输入对土壤固碳的贡献.结果表明:施肥能提高土壤有机碳含量,连续30年不同施肥后,各施肥处理土壤有机碳含量趋于稳定,有机无机配施的土壤有机碳含量为21.02 ~ 21.24 g?kg~(-1),增加速率为0.41 ~ 0.59 g?kg~(-1)?a~(-1),单施化肥的土壤有机碳含量为15.48 g?kg~(-1).各有机无机肥配施处理土壤的平均有机碳储量为43.61 ~ 48.43 t C?hm~(-2),历年平均土壤有机碳储量显著大于单施化肥处理.土壤固碳速率与年均投入碳量呈显著指数正相关.本试验条件下,每年需要增加外源有机碳为0.12 t C?hm~(-2)才能维持土壤有机碳的平衡.
摘要：
Experiments were conducted to determine the effects of three types of coated urea on the accumulation of cadmium (Cd) in rice (Oryza sativa L.) grown in contaminated soil. Pot-culture experiments were conducted in a greenhouse from July to November 2012 on the rice cultivar “Hua Hang Si Miao” in Guangzhou (China). The experimental design was completely randomized with four treatments and three replications. The treatments were control (CK) (N 0 mg/kg), prilled urea (PU) (N 200 mg/kg), polymer-coated urea (PCU) (N 200 mg/kg), and sulfur-coated urea (SCU) (N 200 mg/kg). Our results indicated that applications of PCU and SCU slightly increased the dry weight of rice grains. The application of SCU significantly decreased the CaCl2 and toxicity characteristic leaching procedure (TCLP)-extractable Cd concentrations by 15.4 and 56.1 %, respectively. Sequential extractions showed that PCU and SCU applications led to a significant decrease in Cd in the exchangeable fraction and an increase in the bound iron (Fe) and manganese (Mn) oxides fractions. Cd concentrations in grains treated with PCU were reduced by 11.7 %, whereas SCU significantly reduced Cd concentrations by 29.1 %. SCU reduced Cd transfer from the straws to the grain. Our results demonstrated that PCU and SCU may be effective in mitigating Cd accumulation in rice grown in acidic Cd-contaminated soil, especially in plants receiving SCU.
摘要：
In tropical and subtropical soils, sesquioxides and soil organic matter (SOM) are major binding agents for aggregates. However, the biotic and abiotic contributions to aggregation are often difficult to distinguish. In this study, we attempted to assess their contributions to aggregation separately, as indicated by aggregate size distribution and specific surface area (SSA). Our objectives were (i) to determine aggregate size distribution and SSA before and after removal of sesquioxides and SOM, and (ii) to assess the contributions of sesquioxides and SOM to soil aggregation. An oxide-rich Ultisol under long-term fertilization was extracted by water as a control, oxalate, dithionite-citrate-bicarbonate (DCB), or by H<inf>2</inf>O<inf>2</inf> in the absence of any physical disturbance. The aggregate size distribution, Fe/Al oxides, soil organic C (SOC), and SSA of the soil before and after extraction were determined. Our results showed that the DCB and oxalate solutions broke down the sand-sized aggregates most intensively, whereas the H<inf>2</inf>O<inf>2</inf> treatment disrupted 0.25-2.0mm aggregates intensively, indicating that SOM is the major binding agent for aggregates of this size. A slight change either in SOC stock after removal of Fe/Al oxides by DCB and oxalate or in Fe/Al oxides after removal of SOC by H<inf>2</inf>O<inf>2</inf> indicated that organo-mineral complexes are a minor binding mechanism of aggregation in the soil studied. The SSA was reduced by 72-84% in the soil extracted by DCB, followed by 32.0-35.9% after the oxalate extraction, whereas the removal of SOM increased SSA by 3.8-12.6%. Our results showed that Fe/Al oxides played a major role in aggregation in the Ultisols studied. The difference in the major binding agent for different aggregate size classes is another reason to explain why the hierarchy aggregate concept is not applicable to oxide-rich soils. This study, however, could not assess their contributions to soil aggregation precisely, because of the difficulty in tracing aggregate dynamics. To better understand the mechanisms of soil aggregation we need more works in the future.
