/AnMtgsAbsts2009.55089 How Does the Management-Induced Change in Soil Organic Matter Control Carbon Dynamics and Organo-Mineral Associations in a Volcanic-Ash Soil in Central Japan?.

Tuesday, November 3, 2009
Convention Center, Exhibit Hall BC, Second Floor
Rota Wagai1, Ayaka Kishimoto2, Seiichiro Yonemura2, Yasuto Shirato2, Syuntaro Hiradate2 and Masao Uchida3, (1)Carbon and Nutrient Cycling, Natl. Inst. Agro-Environ. Sci., Ibaraki 305-8604, Japan
(2)National Institute for Agro-Environmental Sciences, Ibaraki, Japan
(3)Environmental Chemistry Division, Natl. Inst. of Environmental Sciences, Ibaraki 305-8506, Japan
  • 2009-11_SSSA_meeting_Wagai_et_al.pdf (1.1 MB)
  • Volcanic-ash soils hold significantly greater amounts of organic matter (OM) than non-volcanic soils largely because inorganic constituents unique to such soil (e.g., poorly-crystalline minerals) have high capacity to stabilize OM. Better understanding of stabilization and destabilization processes is critical to effectively manage volcanic-ash soils for C sequestration and fertility. Here we focused on an allophonic Andisol from a long-term experimental field (Tsukuba, Japan) and compared three surface soil samples (0-20 cm) of contrasting OM contents that resulted from agricultural practices. We examined how C mineralization rate, its temperature sensitivity, and OM distribution across different organo-mineral assemblages change along the gradient of soil OM contents. One soil was from the plot under no-tillage plus leaf-manure addition for two decades and had 10% total C (NT soil), presumably representing a maxima. Another soil with no fertilizer/manure treatment had 4% OC (NF soil), representing a minimum OM content for surface soils in the area. The last soil was from conventional tillage with no manure and had 5% C (CT soil). One-month lab incubation showed that the amount of respired C as well as the fraction of total C respired increased in the following order: NF < CT < NT 5-20cm < NT 0-5cm, suggesting that NF soil had the lowest amount and quality of C. Temperature sensitivity (Q10) was higher for NF. The rest of samples, however, had similar Q10 despite 3-fold difference in total C and 9-fold difference in respired C among them, indicating non-linear response of Q10 to soil C pool size. We will also present our initial results on C structure based on 13C-NMR as well as the distribution of OM and extractable Fe, Al, Si (by oxalate and pyrophosphate) among density fractions.