Nitrous oxide and carbon dioxide production in soils from the 46-year long term fertilization treatments in response to temperature and moisture changes

Chuleeporn Sriyam, Amnat Chidthaisong*, Kazuyuki Yagi, Sirintornthep Towprayoon and Sudarut Tripetchkul

<p><strong>Abstract:</strong> This study aimed to determine the rates of N<sub>2</sub>O and CO<sub>2</sub> production under different soil temperature and moisture conditions.
Soil samples were collected from the 46-years long-term fertilizer experiment plots in Lopburi province. Three treatments were
included in the present study; control or no fertilizer (NF), chemical fertilizer application (CF) and organic fertilizer application (OM).
The soils were incubated at 25°C, 30°C, and 35°C under moisture content of 60 and 80% water-filled pore space (%WFPS) for 14 days.
Long term fertilizer experiment (46 years) revealed that the application of cow or chicken manure has increased soil carbon stock
(SOC) by 5-7 MgC ha-1 compared to that of no fertilizer and chemical fertilizer application. The N<sub>2</sub>O production rate from all treatments
was increased 2-9 times under 60% WFPS and 5-18 times under 80% WFPS when the temperature was increased from 25° to 30°C,
but was decreased when the temperature was increased from 30° to 35°C, except the CF which was increased. The OM had highest
N<sub>2</sub>O and CO<sub>2</sub> at any temperatures investigated. Only the temperature above 30°C that the effects of moisture on N<sub>2</sub>O production was
observed. The mean value of N<sub>2</sub>O production in OM under 60% WFPS and 80% WFPS differed only under 25°C. On the other hand,
CO<sub>2</sub> production rates was enhanced 1-2 times along with increasing temperature and moisture. These results indicate that the longterm fertilizer application has significantly changed the production potential of N<sub>2</sub>O and CO<sub>2</sub>, and so their sensitivities to temperature
and moisture changes.
</p><p><strong>Keywords:</strong> Long-term experiment, N<sub>2</sub>O and CO<sub>2</sub> production, soil temperature, soil moisture.</p>

Experimental investigation of external PV slats for daylighting in Thailand

Damson Daniel Kadete, Pipat Chaiwiwatworakul* and Surapong Chirarattananon

<p><strong>Abstract:</strong> This paper presents an investigation of the daylighting from external multiple shading slats integrated with photovoltaics
(PV). Experiments were carried out at an outdoor chamber with a south-facing window. Based on the measured results using various
sensors, the daylighting characteristics were analyzed for an office environment under varying tropical sky conditions. Relationships
of the exterior daylight illuminance and the interior daylight distribution could be empirically formulated, and they were used to
determine the required artificial light from electric lamps to supplement the transmitted daylight from the window. In the assessment
of the daylighting potential of the PV shading slats, a monthly adjustment scheme of the slat angle to fully intercept the direct sunlight
from the south window was proposed together with the task-ambient lighting concept. By using our experimental room as the
demonstration case, the analysis showed that the daylighting of the PV slat system could reduce the lighting energy consumption by
80% compared to the typical office case designed with the uniform lighting concept. The generated solar energy from the PV array on
the slat surface was estimated to be sufficient for the lighting by the direct-current LED lamps. However, battery storage was required
due to the time mismatch between the solar power generation and the required electricity for supplement lighting.
</p><p><strong>Keywords:</strong> Daylighting, dimmable lighting, PV slats, tropical climate, workplane illuminance. </p>