Assessing soil organic carbon in relation to land use management using a portable hyper spectral camera in andisols

Soil micro- and macro organisms contribute a wide range of essential services to the sustainable function of all ecosystems by acting as the primary driving agents of nutrient cycling by, for example, regulating the dynamics of soil organic matter, soil carbon sequestration and greenhouse gas emission; modifying soil physical structure and water regimes; enhancing the amount and efficiency of nutrient acquisition by vegetation; and by enhancing plant health (Komatsuzaki and Ohta, 2007). Therefore, soil organic carbon (SOC) monitoring may be a very important technique because SOC changes are strongly associated with the global carbon cycle. To make appropriate decisions for soil and land use management, simple and convenient SOC detective methods should be developed. This paper aims to evaluate the potential of portable spectral camera techniques to measure SOC content in different types of land use. An experiment was set up at the Field Science Research and Education Center of Ibaraki University, which is located in Ami, Ibaraki, Japan (36 deg 01 min N, 140 deg 01 min E). The soil type in this area (in the Kanto region) is Humic Allophane, a type of andisol. A total of 136 soil samples were taken at different types of land use sites including fields, grasslands, windbreak areas forested by broad leaved trees or pine trees, and orchards at the ground surface layer (0-2.5 cm). At each point, 3 samples were taken and dried, ground and analyzed for soil spectra and C-N coder. Partial least square (PLS) regression with validation was used to calibrate the spectral data. Soil spectral characteristics were significantly affected by the SOC content. Reflectance tended to decrease as the SOC content increased. A high correlation was observed between predicted SOC content and actual SOC content in different land use types. Consequently SOC changes due to land use management may be easily monitored by farmers or other technicians using this method.