In this Photo:
Fishermen off Koh-Chang, Thailand's second largest island. Photo by Chjab.
For the environmental data, there is one rain gauge per village and 20 soil moisture/stress meters per village. In addition, in the first 12 months water chemistry analysis was conducted. Other water measurements have continued. As mentioned earlier, soil samples with plot photos were taken and soil questionnaires for each of the 45 households were administered. Consequently, the environmental measurements include soil analysis, plot photos, daily rainfall, soil moisture, water chemistry, and other bi-weekly water measurements. This ongoing data collection includes at the time of writing (October 2009) more than 100 months of data collection.
Both the macrosurvey and microsurvey soil samples were analyzed for four conservative soil fertility indicators: cation exchange capacity (CEC), pH, organic matter content (OM), and field capacity (FC) (Weischet and Caviedes 1993), as well as foliar nitrogen. Field capacity was determined using a laboratory centrifugation method (Cassel and Nielsen, 1986). Field and laboratory methods for pH, CEC, OM and foliar nitrogen are described in Landon (1991) and Lal and Sanchez (1992). Several leaves were collected from plants on the plot and analyzed for total Nitrogen. Foliar nitrogen can indicate level of soil fertility, but more commonly is related to use of nitrogenous fertilizer. Soil and foliage samples were analyzed in the laboratory at Kasetsaat University under the supervision of Professor Irb Keorhumramne, Department of Soil Science.
Soil Moisture Tension (and Soil Temperature)
Checked weekly at five locations in each microsurvey village. Soil moisture tension is also measured at these same five locations at two-day intervals after storms until tension stabilizes or it rains again.
In-situ Water Chemistry
Temperature, pH, and conductivity is measured bi-weekly at five locations in each microsurvey village, mostly in ponds, streams, or canals. In a few cases, measurements are taken in rainwater cisterns to examine rainfall chemistry and wells to examine groundwater chemistry. In-situ water chemistry is also measured after the first rain of each month, to capture the "first-flush" water quality in general terms.
Lab Water Chemistry
The first year Microsurvey of the water chemistry included, in addition to the field measurements in year three: Total Nitrogen, Organic Nitrogen, Ammonia-Nitrogen, Nitrite Nitrogen, Nitrate Nitrogen, Ortho-Phosphorus, and Total Phosphorus. This was measured through samples from all water stations - again, five per village - once per month for twelve months.
One rain gauge is checked each day in each microsurvey village.
For each plot with a soil sample, the enumerator took photographs from the center of the field in the four cardinal directions and one photograph diagonally across the field. The enumerator also described the general characteristics of the surrounding landscape, including vegetation present, topography, and proximity to bodies of water.
Photos of each of the initial survey villages were obtained, including the earliest in the 50's and the latest in the 80's.