Roengsak Katawatin

Introducing mungbean as a preceding crop to enhance nitrogen uptake and yield of rainfed rice in the north-east of Thailand

One possible management option for farmers to improve the soil nitrogen (N) supply for rice production is the cultivation of a prior legume. The objective of this study was to investigate the value of such an option in the lowland of the north-east of Thailand. Two experiments were established in 2 typical locations in a split-plot design with 4 replicates. The main plots included 3 nitrogen levels (0, 30, and 60 kg N/ha) and the subplots, 4 pre-rice managements: (i) fallow with weeds removed (FW–); (ii) with weeds incorporated before the rice crop (FW+); (iii) mungbean incorporated at flowering as green manure (MGM); or (iv) incorporated after grains harvest (MR+). In both experiments the difference in rice yield between MGM and MR+ was not significant. In Expt 1, in contrast to Expt 2, the rice yield increase due to MR+ was significant and significantly higher than that due to application of 60 kg N/ha. Moreover, significantly higher apparent recovery of N (ANRm, kg N uptake increase/kg N supplied by residues), probably due to the continuous flooding of the soil surface, was achieved in this experiment. The low values of internal efficiency of N (IEN, kg total grains/kg total N uptake), ANRf (Δ kg N uptake/kg N supplied by fertiliser), and of ANUEf (Δ kg grains/kg applied N fertiliser) recorded in the MR+ treatment of Expt 1, suggest that no application of N fertiliser is needed where the soil water conditions allow high recovery of the N supplied by a preceding mungbean crop.

Use of LANDSAT-7 ETM+ with ancillary data for soil salinity mapping in Northeast Thailand

Soil salinity is a major environmental constraint in Northeast Thailand. Sustainable land use and management in this region require careful mapping of the salinity status. This study was conducted to investigate performances of some digital classification techniques for soil salinity mapping in the Northeast. The techniques investigated were based on the use of LANDSAT-7 ETM+ with different combinations of three kinds of ancillary data (i.e., topography, geology, and underground water quality). In this study, the Maximum Likelihood classification method was employed. Statistics including KAPPA analysis and Z-statistic, overall accuracy, producers accuracy, and users accuracy, were used as the bases for assessments of mapping accuracies and, in turn, performances of the classification techniques. Results have shown that the use of ETM+ data bands 4,5 and 7, with the combination of all three kinds of the ancillary data yielded the most accurate soil salinity map with 83.6 % overall accuracy. The same subset of ETM+ data when used with any combination of two kinds of the ancillary data could serve as well. Other classification techniques yielded significantly less accurate results. It was, therefore, concluded that techniques based on the use of the selected ETM+ data subset with combinations of two or three kinds of the ancillary data were promising.

Field-scale Spatial Variability of Electrical Conductivity of the Inland, Salt-affected Soils of Northeast Thailand

This article goes beyond the historical narratives to apply scientific methods to the archaeological studies of the ancient kingdom of Tambralinga in Southern Thailand. Its objectives are (1) to examine the geography related to agriculture and settlement pattern using data from ground surveys, aerial photographs, and Geographical Information System, (2) to determine the dates of some important brick shrines using data from the themoluminescence dating technique, and (3) to reveal the layout of the ancient Khao Kha religious complex using the data from the Structure-from-Motion technology in the area of Sichon District, Nakhon Si Thammarat Province. It proposes that the ancient communities of approximately the 6 th to 11 th centuries CE lived in the areas suitable for wet-rice cultivation, with sufficient supply of water and alluvial soils. It may also be hypothesized, based on the calculation of the amount of rice produced in the floodplain, the density and dates of brick shrines, and the complicated layout and massiveness of the Khao Kha religious complex, that this area between the Tha Khwai, Tha Chieo, and Tha Thon rivers in Sichon District was one of the most significant centers in the Tambralinga Kingdom.Dengue is a viral disease, transmitted by Aedes aegypti , and is still a big problem in tropical areas, including Indonesia, where the temperatures are relatively warm and suitable for vector mosquito life. In the dry season, the day and night temperature differences are quite sharp and, at that time, the number of dengue cases is low. In this study, the difference between day and night temperature is referred to as daily temperature fluctuation and represented by the maximum and minimum temperature difference in each month. The research was conducted in Sleman Regency, Yogyakarta Province, Indonesia, as an endemic area, and the data were collected from 4 endemic areas in Sleman; Gamping, Godean, Sleman, and Depok districts. The data collected were quantitative with serial data retrospective. Secondary data of monthly dengue incidence in the years 2008 - 2013 were obtained from the Regency Health Office and used as a dependent variable. Monthly minimum and maximum temperatures in the same periods were obtained from the Agency of Meteorology, Climatology, and Geophysics. The differences between the minimum and maximum temperatures were calculated, to be used as independent variable data, and represented the different day and night temperatures of the month. Data were analyzed by using linear regressions to determine the influence of fluctuating temperature on the incidence of dengue. Results show that fluctuating temperature affected dengue incidence in the districts of Godean (p = 0.000; R 2 = 0.207) and Gamping (p = 0.006; R 2 = 0.125), but did not affect it in Sleman (p = 0.164) or Depok (p = 0.075). The data suggests that fluctuating temperature affected dengue incidence with powers of 20.7 % in Godean and 12.5 % in Gamping.

Spatial Variability of Sodium Adsorption Ratio and Sodicity in Salt-Affected Soils of Northeast Thailand

Information on spatial variability of Sodium Adsorption Ratio (SAR) is useful for implementation of appropriate control measures for the salt-affected soils. The major objective of this study was to use geostatistics to describe the spatial variability of (i) the SAR and consequently (ii) the soil sodicity, in areas of different classes of salt-affected soils. Attention was on areas of very severely salt-affected soils (class 1), severely salt-affected soils (class 2), and moderately salt-affected soils (class 3). For each class, 2 study sites were chosen, totally 6 sites were taken into consideration. In each site, 100 soil samples were collected at 0-30 cm depth according to the stratified systematic unaligned sampling method in the dry season of 2012, and analyzed for the SAR in the laboratory. Descriptive statistics and Geostatistics were applied to describe the variability and spatial variability of SAR and soil sodicity, respectively. The result revealed very high variability of SAR. Descriptive statistics showed the CV values of ≥ 35% for every site of every class. When using semivariogram to describe the spatial correlation of SAR, it was found that in 3 study sites, the semivariogram models fitted well with the corresponding semivariogram samples indicating spatial correlation of SAR in the areas. In these cases, the Ordinary Kriging was applied to generate soil sodicity map. The relatively short range values especially for class 1 indicated very high variation of SAR. However, for the other 3 study sites, the linear models were fitted indicating no spatial correlation. Consequently, Trend Surface Analysis was applied instead. According to the soil sodicity maps generated in this study, the areas of class 1 were entirely occupied by strongly sodic soils. For classes 2 and 3, the soils in all study sites belonging to these classes included normal and slightly sodic soils of different proportions. Furthermore, inconsistency of the spatial variability patterns of SAR was found even in areas within the same class of salt-affected soils. As a result, prior to the intensive management of this problem soil in a particular area, investigation on the spatial variability pattern should be performed