สัณฐานวิทยาและสมบัติของดินในระบบวนเกษตรที่มีกาแฟเป็นพืชหลักในจังหวัดเชียงใหม่

Abstract

A study on soil morphology and properties in coffee-based agroforestry systems in Chiang Mai province were investigated by selecting 3 districts, 8 pedons. The aim of this study was to investigate soil morphology in the field include the plant species diversity. Then, the soil samples were analyzed for physical, chemical and mineralogicalproperties in laboratory according to standard methods. The results showed that pedon 1, pedon 2 and pedon 3 in Doi Saket district were soils in agroforestry systems (12, 12 and 17 year-old coffee, respectively) while pedon 4 was soils in natural forest (hill evergreen forest). In Mae Rim and Mae Taeng districtspedon 5 was soils in natural forest (hill evergreen forest) while pedon 6, pedon 7 and pedon 8 were soils in agroforestry systems (9, 9 and 12 year-old coffee, respectively), where the elevation was 720-1,005 meters above mean sea level. These areas are slightly undulating to very steep slope area. Most of the pedons were residuum from granite, except pedon 3 was colluvium form granite while pedon 5 was residuum from gneiss metamorphism form granite. Development of most of the pedons soil profile were A-AB-BA-Bw-BtBCr-Cr-R, classification of soil order was Ultisols, subgroup was Typic Palehumults and Typic Haplohumults, except pedon 3 which the soil profile was A-Bw-BC, classification of soil order was Inceptisols, subgroup was Typic Humudepts. Most of the pedons were very deep soil, except pedon 1 was deep soil. Soils in agroforestry systems, topsoil was dark reddish brown and dark brown. Soils in natural forest, topsoil was dark brown and brown, all pedon in subsoil were dark reddish brown to red. Soil structure of all pedon in topsoil was granular while, subsoil was angular and subangular blocky. In agroforestry systems, it found that soil texture in topsoil was sandy clay loam to sandy clay; subsoil was sandy clay loam to clay. In natural forest, it found that soil texture in topsoil was sandy clay loam and sandy clay; subsoil was clay loam and clay. Gravel content, particle density, total porosity, field capacity, permanent wilting point and available water capacity of topsoil was similar between topsoil and subsoil. Bulk densityof topsoil was lower than subsoil. Soil:water reaction (1:1) in topsoil and subsoil of all pedons were very strongly acid to moderately acid. Soil:potassium chloride reaction (1:1) in topsoil and subsoil of all pedons were extremely acid to very strongly acid. Organic matter content, total nitrogen, available phosphorus, extractable calcium, extractable magnesium, extractable bases, extractable acidity, cation exchange capacity and base saturation of topsoil were higher than subsoil. Available potassium of topsoil was very high while, it was very from low to very high in subsoil. Extractablepotassium of topsoil to subsoil wasvery diverge, which topsoil showed low to very high level and very low to high in subsoil. Extractable sodium both topsoil and subsoil were very low. For mineralogical characteristics, soil in all pedons composed with clay-size particles mainly gibbsite. Soil fertility assessment showed that topsoil was medium, while moderately low in subsoil. Soil suitability assessment was unsuited because there is a limitation on topography. The species richness of plot in natural forest showed higher number than plot in agroforestry systems. However, plant density between them was similar. Ficus altissima Blume, Toxicodendron succedaneum (L.) Kuntze, Schima wallichii (DC.) Korth. and Adenanthera pavonina L. were the dominatedspecies. Ecological importance value index of all plots in agroforestry systems was Coffea arabica L. In natural forest, ecological importance value index was Schima wallichii (DC.) Korth. Plant biomass and plant nutrient storages of plot in natural forest had higher than plot in agroforestry systems.