Analysis on properties of sugarcane growing soils in Northeast Thailand

Analysis on properties of sugarcane growing soils in Northeast Thailand was carried out on soils of 10 areas. Methods of study included pedon analysis of soils in the field, laboratory analysis of soil physical and chemical properties, mineralogical and micromorphological characteristics and suitability assessment of soil properties based on sugarcane requirements. Soils in the study area include Quartzipsamments, Paleustalfs, Haplustalfs, Plinthustalf and Paleustults on old alluvial terraces and eroded low hills. They are very deep soils developed on old alluvial terraces and eroded low hills. They are very deep soils, developed on old alluvium or wash deposits overlying residuum derived from sandstone. Their skeleton materials include mainly of subrounded to subangular quartz grains and with nodules of iron and manganese in some areas. Clay coats are present in their subsoils. Laboratory analytical results indicate their variable physico-chemical properties. Their texture ranges from sand to sandy clay loam. They have moderately low to moderately high bulk density (1.38-1.76 Mg/cubic m) and very low to high hydraulic conductivity (0.01-14.91 cm/hr). Their reaction ranges from extremely acid to mildly alkaline (pH 3.93-7.45). The soils have low to very low organic matter and total nitrogen (8.6-0.4 g/kg and 0.28-0.04 g/kg respectively), very high to very low available phosphorus (359-0.04 m/gkg) and medium to very low available potassium (69.95-3.45 mg/kg). Their total extractable bases are medium to very low (7.36-0.32 cmol/kg), and their extractable acidity varies from moderately high to very low (7.0-0.5 cmol/kg). They have medium to very low cation exchange capacity (11.7-1.9 cmol/kg). Their base saturation percentage ranges from high to low (92-14 percent) and electrical conductivity values are generally very low (0.39-0.02 dS/m). Their clay fraction is relatively small and dominated by kaolinite. Though some of these soils have medium fertility and have no specific limitation of sugarcane production, most of them have low fertility status deriving from the low amount of nutrient and poor exchange properties. These strongly suggest their chemical property as being the major factor controlling growth and productivity of sugarcnae in the study area. A recommended approach for soil management, thus, includes the emphasis on maintaining organic matter level in the soils above 10 gram per kilogram in their surface layer, and the application of complete fertilizers. If possible, the fertilizers should be in a slow-release form to minimize the loss by leaching.