MINERAL CONTENT OF GRASSES AND GRASSLANDS OF THE HIMALAYAN REGION

Abstract

We analyzed soil samples, collected from naturally occurring grasslands of the Himalayan region, to investigate trace element distribution in soil profiles and their concentrations in surface soils, as well as to examined frequency and geographical distribution of low and high levels of trace elements. Both chemical and radiochemical analytical techniques were employed to determine the trace elements. This study was part of a research project on the evaluation of mineral contents of natural grasslands and grasses and the relation-ship between the mineral contents in grasses and grasslands. Little or no variation in the content of total Zn, Mn, Cu, Cd, Ni, Pb, Co, and I from surface to subsurface horizons in the soil profiles was observed. However, the concentrations of extractable Zn, Mn, Cu, and B in the surface horizons were higher than in the subsurface horizons. The variations among the profiles were primarily related to the geological material from which the soils derived. Means and ranges of trace elements are given for particular locations and for the whole sample area. Concentrations of most of the trace elements varied greatly among sites at the same location and among locations. Generally soils from the subhumid tropical climate derived from sedimentary rocks were poorer in most of the elements than those from the temperate climate derived from igneous or metamorphic rocks. However, some exceptions to this generality were observed. There were highly significant correlations between the contents of trace elements, especially total Zn and Mn, and extractable Zn, Fe, Ni, Co, B, and I, and the soil chemical properties, elevation, rainfall, and temperature. Rainfall and temperature showed negative correlations for almost all the trace elements. A number of the trace elements were interrelated in their geochemical origin. On the basis of the critical levels suggested for trace elements deficiencies, proportions of the samples that may be considered deficient were about 28% for Zn, 50% for Mn, 20–30% for Cu, 4% for Fe, 56–87% for B, 77% for Mo, and 5–10% for Co.