 หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Effects of Moisture and Temperature on Respiration in Tropical Forest and Agricultural Soils) ผู้เขียน: Siriporn Wiriyatangsakul, Amnat Chidthaisong, Sudarut Tripetchkul, Pitayakorn Limtong สื่อสิ่งพิมพ์:pdf AbstractSoil respiration in tropical uplands was studied in agriculture (maize) and dry evergreen forest soils. The objective of this study was to investigate the effects of moisture and temperature on soil respiration. Diurnal variations of in situ soil CO2 efflux was studied in May 2004 and February 2005. In the laboratory, soil respiration in a short-term incubation was measured under various moisture contents (air-dry, 25, 50, 75 and 100%WHC) and various constant temperatures (10?C to 45?C). In situ soil CO2 flux showed strong diurnal patterns correlated with both air and soil temperature. CO2 efflux from both study sites increased to the maximum values during the late afternoon, usually 2-4 hours after a peak in air temperature. The total soil CO2 fluxes integrated over the measurement period were 1354 and 3082 mg CO2 m-2 day-1 at agricultural site and 1467 and 12851 mg CO2 m-2 day-1 at forest site in May 2004 and February 2005, respectively. The Q10 value for agricultural site estimated from relationship between soil temperature at 5 cm and CO2 flux was 3.37 (May 2004). For the forest site, the Q10 was 2.04 (February 2005). Results from laboratory study indicated that the topsoil layer (the top 20 cm) contributed mainly to the overall respiration. Soil respiration was highest at moisture between 50% and 75% WHC. The Q10 values of agricultural soil were higher than of that of the forest soil, indicating relatively higher sensitivity of the agricultural soil to temperature change than the forest soil. Laboratory results also indicated that subsoil was more sensitive to temperature and moisture changes than topsoil. |
หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Denitrification Power of the Flooded Rungsit Very Acid Soil ) ผู้เขียน: นายสมศักดิ์ วังใน, รองศาสตราจารย์ , Vithaya Thananusone, Pitayakorn Limtong สื่อสิ่งพิมพ์:pdf AbstractA study was conducted by addition of ammonium and nitrate fertilizers into the Rangsit very acid soil, the soil was flooded, the rice seedlings were transplanted, and denitrification activity including ammonium and nitrate contents were followed. Results revealed that denitrifying microorganisms, in both ammonium and nitrate fertilized soil, increased rapidly and reached their peaks approximately 3 to 4 weeks after submergence. Approximately 1/7 of the added ammonium was transformed to nitrate, of this 71 percent (or 10 percent of the ammonium nitrogen added) was lost via nitrification-denitrification sequence. Eighty four percent of nitrate (or 86 percent of the nitrate nitrogen added) was denitrified and lost from the nitrate-treated soil. The rice yield obtained from the ammonium treated soil was significantly higher than that nitrate treated soil. |