Spatial variation and distribution of soil micronutrients relative to macronutrients in Mt. Wakakusa Grassland (central-western Japan)

Abstract

To provide spatial information on soil resources for sustainable land management in the Mt. Wakakusa Grassland of central-western Japan, we investigated the spatial variation and distribution of selected micronutrients, i.e., Mehlich 3 extractable Fe, Mn, Cu, and Zn (referred as M3-Fe, M3-Mn, M3-Cu, and M3-Zn, respectively), in surface soils (0–5 cm in depth) of the grassland. All micronutrients showed intermediate variability, with coefficients of variation ranging from 26.9 to 48.9%. The M3-Fe (144.0 ± 32.9 mg kg−1) and M3-Mn (204.8 ± 91.3 mg kg−1) contents were relatively high compared with the optimal level exhibited by M3-Cu (1.8 ± 0.5 mg kg−1) and the low level given by M3-Zn (7.8 ± 2.2 mg kg−1). The availability of these micronutrients, except for M3-Zn, showed more significant correlations with the soil mineral phase than with the soil pH and organic matter. Variogram analysis reveals a moderately weak spatial dependency [nugget-to-sill (N/S) ratio = 0.67] for the M3-Zn, while the other micronutrients (M3-Fe, M3-Mn, and M3-Cu) exhibit moderately strong to strong spatial dependencies (N/S ratio = 0.21–0.50). Interpolation maps created in this study demonstrate locations with toxic levels of M3-Fe and M3-Mn and those deficient in M3-Mn and M3-Cu in the study site. Based on these results, a site-specific soil management scheme is recommended in the Mt. Wakakusa Grassland.