Subscribe Now Subscribe Today
Research Article

Potential of Paddy Soils for Jasmine Rice Production in Si Sa Ket Province, Northeast Thailand

Jiratchaya Saenya, Somchai Anusontpornperm, Suphicha Thanachit and Irb Kheoruenromne
Facebook Twitter Digg Reddit Linkedin StumbleUpon E-mail

A study was conducted to characterize seven areas of paddy soils in Si Sa Ket province, northeast Thailand and to evaluate their potential for jasmine rice production. Field soil survey, soil sampling with respect to genetic horizons and soil analyses were undertaken basing on standard procedures. All soils were Ultisols (Korat (Kt1, Kt2), Roi Et (Re1, Re2), Ubon (Ub) and Thatum (Tm) soil series) with one Alfisol (Phimai soil series, Pm). All soils were deep with poorly drained feature but varied in properties. Their suitability for paddy rice cultivation was moderately (Pm soil) to marginally suitable (Kt1, Re2, Ub and Tm soils) with Kt2 and Re1 soils, both being unsuitable but potentially suitable (N1sn). Soil texture(s) was the major restriction of most soils of which loamy sand to sandy loam topsoil induced rather rapid water infiltration rate and a risk of moisture shortage. There were no soils that had a salinity problem despite reports suggesting a stress induced by soluble salts in soils was essential for jasmine rice to produce fragrant substance. Basing on gained yield data collected which varied from 2.41-2.98 t ha-1, all soils were tentatively suitable for jasmine rice, Khao Dok Mali 105 variety. The highest yield was in Pm soil that was slightly higher than that grown on Tm soils (2.94 t ha-1). These amounts of yield were higher than the potential yield of this variety (2.28 t ha-1). This might be due to the impact of management and it indicated that suitability assessment for paddy rice in general cannot be used to evaluate the potential of these paddy soils for growing jasmine rice. The tentative suitability class for this variety should be in better classes according to this study. Nonetheless, low soil moisture retention capacity in addition to low fertility status of the soils needs to be emphasized. Thus, these soil constraints should be designated in the suitability class for growing jasmine rice on these soils in order to provide basic information and sustainable use.

Related Articles in ASCI
Search in Google Scholar
View Citation
Report Citation

  How to cite this article:

Jiratchaya Saenya, Somchai Anusontpornperm, Suphicha Thanachit and Irb Kheoruenromne, 2015. Potential of Paddy Soils for Jasmine Rice Production in Si Sa Ket Province, Northeast Thailand. Asian Journal of Crop Science, 7: 34-47.

DOI: 10.3923/ajcs.2015.34.47

Received: December 20, 2014; Accepted: March 02, 2015; Published: March 20, 2015


Khao Dawk Mali 105 (KDML105) variety, commonly known as jasmine rice, is a premium quality and very famous in the world market because of its unique long slender grain feature with white color. Moreover, the test is soft and smells like a natural fragrance after cooked (Kongsri et al., 2002). Thailand is the major producer of high-quality aromatic jasmine rice, which commands a premium price in the world market. In 2013, exported jasmine rice earned over 5.74 billion baht for Thailand (Maclean et al., 2002; Vejpas et al., 2005). The lower northeast Thailand sub-region contains nine provinces covering 8.4 million ha, with 17,357 villages and 11.5 million people. About 70% of the agricultural land belongs to the rainfed lowland rice ecosystem (DOA., 2002). Si Sa Ket, one of those provinces located in the region, is the important area for growing rice, mainly jasmine rice, in the country with the amount produced slightly over million ton per year. Jasmine rice is mostly grown under rainfed conditions in the north-east of the country, a region characterized by an undulating landscape with generally poor soils and erratic rainfall (Homma et al., 2003). The salinity in salt affected soils is the major obstacle in achieving a better result (Cha-Um et al., 2009; Cha-Um and Kirdmanee, 2011). All of these soil constraints caused stunted growth and have drastically reduced rice grain yield and average yields for Jasmine rice in north-east Thailand are about 2.33 t ha-1 (Maclean et al., 2002), which is one of the lowest in the world, however, this average yield is slightly higher than that of the potential yield, which is 2.28 t ha-1 (Sri-Aun, 2005). Plant nutrients in soils and available water content during growth period have been listed as major biophysical constraints to increasing yields (Jearakongman et al., 1995; Wonprasaid et al., 1996; Fukai et al., 1998; Khunthasuvon et al., 1998). Besides, the increased aromatic fragrance has been reported (Yoshihashi et al., 2004; Gay et al., 2010; Kaewduang et al., 2013). Although genetic factors play a major role in determining rice aroma (Bradbury et al., 2008), environmental factors and cultivation practices have been shown to substantially affect the aromatic quality of rice. Drought and salinity (Dubey and Singh, 1999; Jedrum et al., 2014; Wanichananan et al., 2003) and soil with low level of availability nitrogen and phosphorus but with high sodium concentration may have a positive effect on the aromatic quality of rice.

In assessing the suitability of soils for crop production, soil requirement of crops must be known. Also, these entire requirements must be understood within the next context of limitations imposed by land forms and other features which do not form a part of the soil but may have a significant influence on use that can be made of the soil. Soil suitability classifications are based on knowledge of crop requirement, of prevailing soil conditions, qualifies in broad terms to what extent soil conditions match the areas. The suitability of soil for paddy rice based on FAO framework system is used in cases of growing long grain rice varieties but not specifically for jasmine rice. Jasmine rice has different characteristics from other long grain rice varieties; therefore it may need differences in land quality that is used in the FAO methodology for the assessment of suitability class. Therefore, this study on the vital soil characteristics of jasmine rice cultivated soils was required to evaluate their true potential for jasmine rice production. This result would be used as a basic knowledge for initiating proper soil management that can be implemented in these soils.


Description of the study site: Si Sa Ket province is located in the southern part of the northeast, Thailand between latitude 14°20'-15°40'N and longitude 103°45'-104°55'E (Fig. 1). This province produces the largest amount of rice, mostly jasmine rice, accounting for more than 0.17 Mt. Traditionally, jasmine rice in this region could be grown under rainfed condition only one crop per year, from July to November.

Seven locations of jasmine rice, KDML 105, growing area in this province were representatively chosen (Fig. 1). The soils selected were in boundaries of Korat (Kt1, Kt2), Roi et (Rt1, Rt2), Ubon (Ub), Thatum (Tm) and Phimai soil series. These areas are under tropical savanna climate with annual rainfall and mean temperature between 2000-2012 being 1,480.4 mm and 27.8°C, respectively (World® Weather Online, 2014).

Image for - Potential of Paddy Soils for Jasmine Rice Production in Si Sa Ket Province, Northeast Thailand
Fig. 1: Location of soil sampling sites (★) in the Si Sa Ket province

Field survey methods consisted of field investigation and soil sampling. Soil profile of each site was dug to the depth of 2 m, if it was able, in order to provide detail soil profile description and sample the soil from all genetic horizons using standard field study procedures and methods (Soil Survey Division Staff, 1993). Jasmine rice grain yield was measured at harvesting stage (110-120 days old) within the area of 4 m2 in each site where soils and their samples were studied and collected.

Laboratory analyses: Laboratory analyses for soil physico-chemical properties were based on standard procedures. Soil samples were air-dried and crushed to pass through a 2 mm sieve and analyzed for the following parameters. The particle size distribution was determined by a combination of sieve and pipette analysis (Day, 1965). Bulk density was determined by a cold method (Blake and Hartge, 1986). Soil pH was determined for a saturation paste, 1:1 soil: water mixture with a pH-meter (National Soil Survey Center, 1996). Organic carbon was determined according to Walkley and Black wet oxidation procedure (Nelson and Sommers, 1996). Soil was extracted by the Bray II method and subsequently the available phosphorus content was determined by the molybdate blue method (Bray and Kurtz, 1945). Extractable Na, K, Ca and Mg were leached from soils with NH4OAc pH 7.0 and their concentrations were measured by Atomic Absorption Spectrometry (AAS) (Peech, 1945). Electrical conductivity (ECe) of a saturation extract at 25°C was measured with an electrical-conductivity bridge (Richards, 1954). The calculation of Sodium Adsorption Ratio (SAR) was carried according to US Salinity Laboratory Staff (1954).

Soil suitability evaluation: Land suitability assessment of soils was done using the FAO framework method (Sys et al., 1991, 1993; FAO., 1976). Data for the requirements of jasmine rice was obtained through the review of various literatures on their morphological characteristics while water requirement and the soil physicochemical requirements of paddy rice were adapted basing on FAO (1976). The parameters used for the land quality assessment is shown in Table 1. The information for the soil unit’s characteristics and crop requirements were matched for each quality to obtain suitability rating. The overall soil suitability classes were obtained using techniques including; principle of limiting condition and arithmetic procedures. Soils were first placed in suitability classes by matching their land characteristics with the agronomic requirements of rice (Table 1).


Soil properties: The soils in this study were developed from different parent materials such as old and local alluvium; wash over residuum derived from siltstone and basalt on undulating surface with slope range of 0.5-5%. The soils were moderately deep to very deep and common profile developments were Apg-Btg and Apg-Btg-Btcg, representing clay accumulation in subsoil horizons (Fig. 2). A presence of indurate plinthite was found in Kt2 and Tm soils, indicating a long dry period over a year in the shallower zone of soils than that of the others. They had thin surface layer with the thickness of 12-21 cm. Soil permeability of these soils was low because of the presence of puddles. These soils had low chroma in matrix and mottles, indicating poorly drained feature and a long period of water logging. The level of ground water table at the time of sampling in dry season was deeper than 200 cm.

The soils had a wide range of textural classes from loamy sand to clay texture with the contents of sand, silt and clay particles ranging from 326-846, 69-339 and 99-378 g kg-1, respectively (Table 2). High bulk density (1.8-2.0 Mg m-3) and slow to moderately slow hydraulic conductivity (0.21-0.65 cm h-1) of the layer directly underneath topsoil (Btg) in all soils reaffirmed that puddling was made in that layer to promote waterlogged condition for growing paddy rice. Most soils exhibited coarse textured characteristics in addition with thin topsoil layer that had insufficient moisture during the growth period of jasmine rice. It was shown by low amount of available water capacity, which accounted in the range between 3.5 and 10.9% by volume except for the Tm soil whose amount was medium (15.2% by volume). This result corresponded to the low content of available water capacity that led to low moisture holding capacity in the soils (Elder and Lal, 2008; Brady and Weil, 2008). This was clearly the major constraint for growing jasmine rice in the area.

Chemical properties and plant nutrient status of the soils chosen were variable (Table 3). The soils were very strongly acid to slightly alkaline, having soil pH in the range of 4.5-7.4. Organic matter content varied between very low to high (0.34-31.99 g kg-1), while total nitrogen contents being very low (0.04-0.52 g kg-1).

Table 1: Soil and environmental conditions for paddy rice production
Image for - Potential of Paddy Soils for Jasmine Rice Production in Si Sa Ket Province, Northeast Thailand
1S1: Suitable, S2: Moderately suitable, S3: Marginally suitable, N1: Actually unsuitable but potentially suitable, N2: Actually and potentially unsuitable, 2Flood sequence defined as duration and depth of flooding, i.e., F32: Flood duration class 3 and flood depth class 2. Tentative classes for duration of floods, class 1 = <2 month, class 2 = 2-3 month, class 3 = 3-4 month, class 4 = >4 month. Tentative flood depth classes, class 1 = <10 cm, class 2 = 10-20 cm, class 3 = 20-40 cm, class 4 = 40-80 cm, class 5 = >80 cm. Flooding depth was to be considered after leveling and grading. F0: No floods, 3Textural class, C: Clay, SiC: Silty clay, SiCL: Silty clay loam, CL: Clay loam, SC: Sandy clay, SCL: Sandy clay loam, Si: Silt, SiL: Silt loam, L: Loam, SL: Sandy loam, LS: Loamy sand, S: Sand. Modified from Sys et al. (1991, 1993)

Phosphorus availability ranged from very low to high (0.16-36.64 mg kg-1) whereas available potassium content varied between very low to low (1.43-43.98 mg kg-1).

Image for - Potential of Paddy Soils for Jasmine Rice Production in Si Sa Ket Province, Northeast Thailand
Fig. 2: Soil profiles and environmental conditions of soils studied

The low amounts of three major plant nutrients show a need of careful fertilization management, especially nitrogen and potassium, when jasmine rice grown on these soils. Typically, the high contents of organic matter and plant nutrient were found in the topsoil and decreased with decreasing depth (Table 3). This was due to the residual effect of cultivation practices in these areas. The soils had very low to very high contents of extractable bases with Ca being a dominant base except for Re1, Re2, Ub and Tb that both Ca and Na were dominant (Table 3). Additionally, very low to very high CEC (0.25-20.75 cmolc kg-1) of soils was closely reflected by the amounts of clay and soil organic matter. This also expressed the soils having very low ability to retain plant nutrients. Values of electrical conductivity ranged from 0.89-0.45 dS m-1 and sodium adsorption ratio was in the range of 0.3-19.8 (Table 3), indicating that salinity and sodicity were not a limiting factor for growing jasmine rice in these areas.

Soil classification: Basing on morphological, physical and chemical characteristics of the soils, most soils were classified as Ultisols (Kt1, Kt2, Re1, Re2, Ub and Tm soils) because of a presence of argillic horizon that had base saturation of lower than 35% at the defined depth (Soil Survey Staff, 2014). This was with the exception of Pm soil that fell into an Alfisol order, owing to base saturation in the argillic horizon of greater than 35%. The Pm soil had a redoximorphic feature throughout the soil profile with a presence of plinthite within 150 cm depth from the mineral soil surface; therefore it was classified into Typic Plinthaqualf at the subgroup level.

For Ultisols, the soils also had the redoximorphic feature and were saturated with water in all layers throughout the soil profile.

Table 2: Physical properties of soils selected
Image for - Potential of Paddy Soils for Jasmine Rice Production in Si Sa Ket Province, Northeast Thailand
Scoring is used for the assessment of physical properties rating of soil according to Kanchanaprasert (1988): Bulk density (Mg m-3): Low: <1.4, Medium: 1.4-1.8, High: >1.8, Hydraulic conductivity (cm h-1): Slow: <0.5, Moderate: 0.5-12.5, Rapid: >12.5, Kti and Kt2: Korat, Pm: Phimai soil series, Re1 and Re2: Roiet, Ub: Ubon, Tm: Thatum

Within 150 cm from the mineral soil surface with increasing depth, there was no clay decrease of 20% or more (relative) from the maximum clay content and the soils had chroma of 3 or more in topsoil.

Table 3: Chemical properties of selected soils
Image for - Potential of Paddy Soils for Jasmine Rice Production in Si Sa Ket Province, Northeast Thailand
Scoring is used for the assessment of chemical properties rating of soil according to Land Classification and FAO Project (FAO., 1973): Organic matter content (g kg-1): Low: <15, Medium: 15-35, High: >35, Available P (mg kg-1): Low: <10, Medium: 10-25, High: >25, Available K (mg kg-1): Low: <60, Medium: 60-90, High: >90, Extractable Ca (cmolc kg-1): Low: <5, Medium: 5-10, High: >10, Extractable Mg (cmolc kg-1): Low: <1, Medium: 1-3, High: >3, Extractable Na (cmolc kg-1): Low: <0.3, Medium: 0.3-0.7, High: >0.7, CEC (cmolc kg-1): Low: <10, Medium: 10-20, High: >20, BS (%): Low: <35, Medium: 35-75, High: >75

Table 4: Land suitability assessment of soils selected for paddy rice production
Image for - Potential of Paddy Soils for Jasmine Rice Production in Si Sa Ket Province, Northeast Thailand

As a result, Kt1, Kt2 and Re2 soils were classified as Aeric Paleaquults with the exception of the Re1 soil that had sandy particle size class throughout a layer extending from the mineral soil surface to the top of the argillic horizon, therefore this soil fell into an Arenic Paleaquult. In the case of Ub and Tm soils, plinthite was found within 150 cm depth from the mineral soil surface; hence they were classified as Typic Plinthaquults (Table 4). However, the plinthite had no part in impeding the growth of jasmine rice root because it was formed in the depth far below rooting zone.

Land suitability classification for jasmine rice production: Sri Sa Ket province is under tropical Savanna climate where the average mean rainfall and temperature over 10 years during the growing season (July-November) of 918.7 mm and 27.6°C, respectively (World® Weather Online, 2014). Therefore, climate, soil depth and ground water table were optimum for growing rice in the study area. Most soils had low fertility status in both topsoil and subsoil mainly due to their low organic matter content, phosphorus and potassium availabilities, low base saturation and low CEC (Table 5), the result was consistent with several reports (Oberthuer and Kam, 2000; Haefele et al., 2006; Boling et al., 2008; Haefele and Konboon, 2009). They also showed poor soil fertility status in northeast Thailand, resulting from low inherent nutrient contents and the dominance of sandy soils.

Most soils (Kt1, Re2, Ud, Tm) were marginally suitable with unfavorable texture (S3s) as strongly limited by predominant sandy particle size class (Table 2). This coarse texture (s) induced rather rapid water infiltration rate and moisture deficiency during growing season. Nonetheless, Pm soil (S2s) was found to be the most suitable for growing rice using normal technology of soil and fertilizer managements with respect to soil and environmental conditions for paddy rice production as shown in Table 1. In some cases as of Kt2 and Re1 they were actually unsuitable but potentially suitable (N1sn) for rice production due to very high sand content in the soils with low nutrient status (n). Regarding slightly undulating surface (2-5% slope), paddy floor must be smoothly graded and high bund was needed for steadily prolonged water storage. This must be taken care very closely and suitably. Although, the nature of soil texture that induced moisture shortage during growing period and reportedly had the adverse effect on reduced yield of jasmine rice, yield survey showed otherwise. Yield data recorded from 7 locations revealed that jasmine rice, KDML 105, grown on all sites chosen gave the yields 3-27% higher than that of yield potential of this rice variety with the yield obtained from Ub soil being the lowest. This indicated that these soils selected were suitable, to some degree, for growing jasmine. This is because jasmine rice is an indigenous variety that is tolerant to doughtiness (Mackill et al., 1996) and barely responds to managements (Bradbury et al., 2008).

Table 5:Fertility assessment of soils selected using some chemical properties of soil in major rooting zone (0-30 and 30-60 cm for topsoil and subsoil, respectively)
Image for - Potential of Paddy Soils for Jasmine Rice Production in Si Sa Ket Province, Northeast Thailand
aOM (g kg-1): <15 = 1, 15-35 = 2, >35 = 3, Avail. P (mg kg-1): <10 = 1, 10-25 = 2, >25 = 3, Avail. K (mg kg-1): <60 =1 , 60-90 = 2, >90 = 3, CEC (cmolc kg-1): <10 = 1, 10-20 = 2, >20 = 3, BS (%): <35 = 1, 35-75 = 2, >75 = 3, bFertility rating: Sum of scores from OM, Avail. P, Avail. K, CEC and BS: <7= Low, 8-12 = Medium, >13 = High

Ragland and Boonpuckdee (1987, 1988) and Ragland et al. (1987) reviewed a number of trials, concluding that, with few exceptions, fertilizer response was abnormally low. Wade et al. (1999) compared fertilizer responses across several countries and found the poorest response at sites in northeast Thailand.

Haefele and Konboon (2009) studied the nutrient management for rainfed lowland rice in northeast Thailand and concluded that soil characteristics between lower and upper fields revealed significantly higher soil fertility for lower fields (higher pH, total organic carbon, total soil nitrogen, CEC, clay and silt content; lower sand content). Across seasons and treatments, grain yields were higher in the valley bottom (2.82 t ha-1) than on upper and middle terraces (1.68 t ha-1). This coincided with surveyed yield of this study (Table 5) that the soils (Kt2, Pm and Tm) located in the lower part of the landscape tended to give a better yield. These yields obtained were higher than that of the reported potential grain yield of jasmine rice, KDML 105 (2.28 t ha-1), therefore, the modification of the suitability assessment specifically for jasmine rice is needed. The tentatively modified class is shown in Table 5. Most studied soils should be placed into at least the second suitability class with suffix indicating some soil constraints such as either fertility limitation (n), drainage (d) or topsoil texture (s). However, there are other soils in this region that could be placed into lower class or in the other word, possess lower potential. Such soils are salt affected soils (saline, sodic and saline sodic soils) that distribute extensively in the area. Reports showed that much lower yields of jasmine rice (0.5-1.1 t ha-1) was obtained by Jedrum et al. (2014) when grown this rice variety on these soils. However, application of crops residues was recommended to improve soil moisture retention and fertility status. These management practices will increase the suitability of theses soils for higher yield and quality in rainfed sustainable production of jasmine rice production in the study area. In contrast, Willet (1995) and Boling et al. (2008) reported a limited and inconsistent yield response to inorganic fertilizer. Contrary to these findings, a large FAO study reported a normal to high fertilizer response (FAO., 1984). Likewise, Khunthasuvon et al. (1998) and Homma et al. (2007) found good responses to inorganic and organic fertilizers.


Seven paddy soils in Si Sa Ket province were chosen for this study. Those were lowland paddy soils with soil colours being indicative of water stagnant. Most soil properties indicated low level of soil quality paddy rice production. There had low fertility status with regard of the contents of organic matter, available phosphorus and potassium, base saturation and CEC. Soil suitability assessment reveled theses soils were moderately to actually unsuitable but potentially suitable with major limitations such as coarse-texture (s) soils in addition with low nutrient status (n). However, the suitability class of these soils did not represent the actual obtainable jasmine rice (Khao Dok Mali 105 variety) yield as shown by the yield surveyed data. All yields obtained were higher than the potential yield of this rice variety, which might be due to cultivating management and the variety being indigenous that subsequently responds differently to soil and environmental conditions as used for the suitability assessment of paddy rice production in general. Improved suitability classes were provided in this study, nonetheless, soil constraints such as risk of water deficit during growing period and lack of plant nutrient reserve along with low ability to retain plant nutrients still remained as a problem that needs to be addressed when grown jasmine rice on these soils.


The authors would gratefully like to acknowledge the Graduate School of Kasetsart University, Bangkok, for research scholarship for international publications.


  1. Blake, G.R. and K.H. Hartge, 1986. Bulk Density. In: Methods of Soil Analysis Part 1: Physical and Mineralogical Methods, Klute, A. (Ed.). 2nd Edn., ASA. and SSSA., Madison, WI., USA., pp: 363-375

  2. Boling, A.A., T.P. Tuong, H. Suganda, Y. Konboon, D. Harnpichitvitaya, B.A.M. Bouman and D.T. Franco, 2008. The effect of toposequence position on soil properties, hydrology and yield of rainfed lowland rice in Southeast Asia. Field Crops Res., 106: 22-33.
    CrossRef  |  Direct Link  |  

  3. Bradbury, L.M.T., S.A. Gillies, D.J. Brushett, D.L.E. Waters and R.J. Henry, 2008. Inactivation of an aminoaldehyde dehydrogenase is responsible for fragrance in rice. Plant Mol. Biol., 68: 439-449.
    CrossRef  |  Direct Link  |  

  4. Brady, N.C. and R.R. Weil, 2008. The Nature and Properties of Soils. 14th Edn., Prentice Hall, New Jersey, USA., ISBN-13: 9780132279383, Pages: 965

  5. Bray, R.H. and L.T. Kurtz, 1945. Determination of total, organic and available forms of phosphorus in soils. Soil Sci., 59: 39-46.
    CrossRef  |  Direct Link  |  

  6. Cha-Um, S. and C. Kirdmanee, 2011. Remediation of salt-affected soil by the addition of organic matter: An investigation into improving glutinous rice productivity. Scientia Agricola, 68: 406-410.
    CrossRef  |  

  7. Cha-Um, S., K. Supaibulwattana and C. Kirdmanee, 2009. Comparative effects of salt stress and extreme pH stress combined on glycinebetaine accumulation, photosynthetic abilities and growth characters of two rice genotypes. Rice Sci., 16: 274-282.
    CrossRef  |  Direct Link  |  

  8. Day, P.R., 1965. Particle Fraction and Particle Size Analysis. In: Methods of Soil Analysis, Black, C.A. (Ed.). Vol. 9. American Society Agronomy, Madison, WI., USA., pp: 545-567

  9. DOA., 2002. Thai local rice varieties. Department of Agriculture (DoA), Office of National Plant Genetics Protection, (In Thailand).

  10. Dubey, R.S. and A.K. Singh, 1999. Salinity induces accumulation of soluble sugars and alters the activity of sugar metabolising enzymes in rice plants. Biologia Plantarum, 42: 233-239.
    CrossRef  |  Direct Link  |  

  11. Elder, J.W. and R. Lal, 2008. Tillage effects on physical properties of agricultural organic soils of north central Ohio. Soil Tillage Res., 98: 208-210.
    CrossRef  |  Direct Link  |  

  12. FAO., 1976. A framework for land evaluation. FAO Soil Bulletin No. 32, Soil Resources Development and Conservation Service Land and Water Development Division, FAO, Rome, Italy.

  13. FAO., 1984. Yield increase through the use of fertilizers and related inputs. 1980-84 Thailand Project Findings and Recommendations, Terminal Report AG: FH/THA/025, FAO, Rome, Italy, pp: 1-33.

  14. Fukai, S., P. Sittisuang and M. Chanphengsay, 1998. Increasing production of rainfed lowland rice in drought prone environments. Plant Prod. Sci., 1: 75-82.
    CrossRef  |  Direct Link  |  

  15. Gay, F., I. Maraval, S. Roques, Z. Gunata, R. Boulanger, A. Audebert and C. Mestres, 2010. Effect of salinity on yield and 2-acetyl-1-pyrroline content in the grains of three fragrant rice cultivars (Oryza sativa L.) in Camargue (France). Field Crops Res., 117: 154-160.
    CrossRef  |  

  16. Haefele, S.M., K. Naklang, D. Harnpichitvitaya, S. Jearakongman and E. Skulkhu et al., 2006. Factors affecting rice yield and fertilizer response in rainfed lowlands of Northeast Thailand. Field Crops Res., 98: 39-51.
    CrossRef  |  Direct Link  |  

  17. Haefele, S.M. and Y. Konboon, 2009. Nutrient management for rainfed lowland rice in northeast Thailand. Field Crops Res., 114: 374-385.
    CrossRef  |  Direct Link  |  

  18. Homma, K., T. Horie, T. Shiraiwa, N. Supapoj, N. Matsumoto and N. Kabaki, 2003. Toposequential variation in soil fertility and rice productivity of rainfed lowland paddy fields in mini-watershed (Nong) in Northeast Thailand. Plant Prod. Sci., 6: 147-153.
    CrossRef  |  Direct Link  |  

  19. Homma, K., T. Horie, T. Shiraiwa and N. Supapoj, 2007. Evaluation of transplanting date and nitrogen fertilizer rate adapted by farmers to toposequential variation of environmental resources in a mini-watershed (Nong) in Northeast Thailand. Plant Prod. Sci., 10: 488-496.
    CrossRef  |  Direct Link  |  

  20. Jearakongman, S., S. Rajatasereekul, K. Naklang, P. Romyen and S. Fukai et al., 1995. Growth and grain yield of contrasting rice cultivars grown under different conditions of water availability. Field Crops Res., 44: 139-150.
    CrossRef  |  Direct Link  |  

  21. Jedrum, S., S. Thanachit, S. Anusontpornperm and W. Wiriyakitnateekul, 2014. Soil amendments effect on yield and quality of jasmine rice grown on typic natraqualfs, Northeast Thailand. Int. J. Soil Sci., 9: 37-54.
    CrossRef  |  Direct Link  |  

  22. Kaewduang, K., S. Thanachit, S. Anusontpornperm and I. Kheoruenromne, 2013. Constraints of salt affected soils for jasmine rice production in Korat Basin. Proceedings of the 39th Congress on Science and Technology of Thailand, October 21-23, 2013, Bangkok International Trade and Exhibition Centre (BITEC), Bangkok, Thailand -

  23. Kanchanaprasert, N., 1988. A study on vital diagnostic features in soil development and land potential evaluation of alfisols and inceptisols in Mae Klong drainage basin. Ph.D. Thesis, Kasetsart University, Bangkok, Thailand.

  24. Khunthasuvon, S., S. Rajastasereekul, P. Hanviriyapant, P. Romyen, S. Fukai, J. Basnayake and E. Skulkhu, 1998. Lowland rice improvement in Northern and Northeast Thailand: 1. Effects of fertiliser application and irrigation. Field Crops Res., 59: 99-108.
    CrossRef  |  Direct Link  |  

  25. Kongsri, N., S. Wongpiyachon and P. Mongkonbanjong, 2002. Identity creation for Thai Hommali rice. Research Development and Biotechnology Institute, Genetic Engineering and Biotechnology Center, Bangkok, pp: 1-105.

  26. FAO., 1973. Soil interpretation handbook for Thailand. FAO Project Staff and Land Classification Division, Department of Land Development, Bangkok, pp: 1-169.

  27. Mackill, D.J., W.R. Coffman and D.P. Garrity, 1996. Rainfed Lowland Rice Improvement. Int. Rice Res. Inst., Philippines, ISBN: 13- 9789712200717, Pages: 242

  28. Maclean, J.L, D.C. Dawe, B. Hardy and G.P. Hettel, 2002. Rice Almanac: Sourcebook for the most Important Economic Activity on Earth. 3rd Edn., CABI Publishing, Wallingford, England, Pages: 253

  29. National Soil Survey Center, 1996. Soil survey laboratory methods manual. Soil Survey Investigations Report No. 42, Version 3.0, Natural Conservation Service, USDA.

  30. Nelson, D.W. and L.E. Sommers, 1996. Total Carbon, Total Organic Carbon and Organic Matter. In: Methods of Soil Analysis. Part 3: Chemical Methods, Sparks, D.L. (Eds.). American Society of Agronomy, Inc., Madison, Wisconsin, USA., ISBN-13: 978-0891188254, pp: 961-1010

  31. Oberthuer, T. and S.P. Kam, 2000. Perception, Understanding and Mapping of Soil Variability in the Rainfed Lowlands of Northeast Thailand. In: Characterizing and Understanding Rainfed Environments, Tuong, T.P. (Ed.). International Rice Research Institute, Manila, Philippines, ISBN: 13-9789712201523, pp: 75-96

  32. Peech, M., 1945. Determination of exchangeable cations and exchange capacity of soils-rapid micromethods utilizing centrifuge and spectrophotometer. Soil Sci., 59: 25-38.
    Direct Link  |  

  33. Ragland, J. and L. Boonpuckdee, 1987. Fertilizer responses in northeast Thailand: 1. Rationale and review of literature. Thai J. Soils Fertil., 9: 65-79.
    Direct Link  |  

  34. Ragland, J. and L. Boonpuckdee, 1988. Fertilizer responses in Northeast Thailand: 3. Nitrogen use and soil acidity. Thai J. Soils Fert., 10: 67-76.

  35. Ragland, J., L. Boonpuckdee and W. Kongpolprom, 1987. Fertilizer responses in Northeast Thailand. 2. Soil acidity, phosphorus availability and water. Thai J. Soils Fert., 9: 122-130.

  36. Richards, L.A., 1954. Diagnosis and Improvement of Saline and Alkali Soils. United States Department of Agriculture, Washington, DC., Pages: 160

  37. Soil Survey Division Staff, 1993. Soil Survey Manual. U.S. Department of Agriculture, Washington D.C., Pages: 437

  38. Soil Survey Staff, 2014. Keys to Soil Taxonomy. 12th Edn., USDA-Natural Resources Conservation Service, Washington, DC., USA., Pages: 360
    Direct Link  |  

  39. Sri-Aun, V., 2005. Tracing the origin of Khao' Hawm Mali. Group of Rice Economic Research, Rice Research Institute, Department of Agriculture, Ministry of Agriculture and Cooperative, Bangkok.

  40. Sys, C., E. van Ranst and I.J. Debaveye, 1991. Land Evaluation Part II: Methods in Land Evaluation. General Administration for Development Cooperation, Brussels, Belgium

  41. Sys, C., E. van Ranst, J. Dehaveye and F. Beernaert, 1993. Land Evaluation Part III: Crop Requirements. Agricultural Publications No. 7, General Administration for Development Cooperation, Brussels, Belgium, Pages: 199

  42. US Salinity Laboratory Staff, 1954. Diagnosis and Improvement of Saline and Alkali Soils. US Department of Agriculture, Washington, D.C., pp: 160

  43. Vejpas, C., F. Bousquet, W. Naivinit, G. Trebuil and N. Srisombat, 2005. Participatory Modeling for Managing Rainfed Lowland Rice Variety and Seed Systems in Lower Northeast Thailand: Methodology and Preliminary Findings. In: Companion Modeling and Multi-Agent Systems for Integrated Natural Resource Management in Asia, Bousquet, F., G. Trebuil and B. Hardy (Eds.). International Rice Research Inst., Los Banos, Philippines, ISBN: 9712202089, pp: 141-163

  44. Wade, L.J., S.T. Amarante, A. Olea, D. Harnpichitvitaya and K. Naklang et al., 1999. Nutrient requirements in rainfed lowland rice. Field Crop Res., 64: 91-107.
    Direct Link  |  

  45. Wanichananan, P., C. Kirdamanee and C. Vutiyano, 2003. Effect of salinity on biochemical and physiological characteristics in correlation to selection of salt-tolerance in aromatic rice (Oryza sativa L.). Sci. Asia, 29: 333-339.

  46. Willet, I.R., 1995. Role of Organic Matter in Controlling Chemical Properties and Fertility of Sandy Soils used for Lowland Rice in Northeast Thailand. In: Soil Organic Matter Management for Sustainable Agriculture, Lefroy, R.D.B., G.J. Blair and E.T. Craswell (Eds.). ACIAR Publisher, Australian, ISBN-13: 978-1863201391, pp: 109-114

  47. Wonprasaid, S., S. Khunthasuvon, P. Sittisuang, S. Fukai, 1996. Performance of contrasting rice cultivars selected for rainfed lowland conditions in relation to soil fertility and water availability. Field Crops Res., 47: 267-275.
    CrossRef  |  Direct Link  |  

  48. World® Weather Online, 2014. Srisaket monthly climate average, Thailand.

  49. Yoshihashi, T., N. Kabaki, T.T.H. Nguyen and H. Inatomi, 2004. Formation of flavor compound in aromatic rice and its fluctuations with drought stress. Research Highlights of Japan International Research Center for Agricultural Sciences (JIRCAS)-2002-2003, pp: 32-33.

©  2022 Science Alert. All Rights Reserved