Assessment of Soil Fertility Status Using Soil Nutrient Index in Three Landuse Systems in Bhutan

Authors: Suraj Chhetri, Tayan Raj Gurung, Tashi Uden, Madhanlal Gurung & Karma Lekphel Jamtsho

ABSTRACT

The study was conducted to assess soil fertility status using soil nutrient index in three land use systems (dryland, wetland and orchard) in Bhutan. The total number of soil samples varied from 71 to 836 depending on soil variables. Soil samples were collected from three different land uses between July 2013 to December 2018, and analyzed, interpreted for pH, organic carbon, organic matter, primary nutrients, carbon/nitrogen ratio, total exchangeable bases, cation exchange capacity and base saturation. The data on soil variables were categorized into very low, low, medium, high and very high classes based on soil fertility ratings and nutrient index. The results revealed that soil reaction in three different land uses varied from strongly acidic to slightly alkaline with pH values varying from 4.04 to 8.20. Soil fertility with respect to organic matter was high in dryland and medium in others. In all the land uses, status of nitrogen was low, organic carbon in medium and CN ratio in good category. The level of available phosphorous and cation exchange capacity was medium in dryland and orchard but low in wetland. Available potassium and exchangeable bases were medium in dryland and low in others. Base saturation was in low category in orchard and medium in other two land uses. A positive and significant correlation of organic matter was found with nitrogen, potassium and cation exchange capacity while significant negative correlations existed between soil pH and nitrogen, organic matter and cation exchange capacity. Based on the criteria for calculating nutrient index value, besides low content of nitrogen in dryland, the soil fertility was characterized as medium in dryland, low in wetland and low – medium category in orchard.

Keywords: Soil fertility, Soil nutrient Index, Land use

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