Development of a Color Chart for Determination of the Soil Organic Matter at Field Level

Abstract

Soil organic matter (SOM) plays pivotal roles in several soil ecosystem processes. It is very important to develop a rapid in-field and easy method for the farmers to measure soil organic matter at the field level. This experiment was carried out in the Department of Soil Science, Bangladesh Agricultural University (BAU), Mymensingh from September 2013 to March 2014 to develop a color chart for the rapid determination of soil organic matter at the field level in formulating efficient fertilizer recommendation for the farmers. Therefore, 47 soil samples were collected from different Agro Ecological Zones (AEZ) covering a sufficient range in texture, soil organic matter and pH for the development of the color chart. Furthermore, the developed color chart was validated by using a set of 16 newly collected soil samples. Thereafter, the organic matter content of the same set of soil was measured by the wet oxidation method, and the soils samples were subdivided into four groups based on the BARC (2005) classification of soil organic matter to compare with the soil organic matter measured by using newly developed color chart. The validation test showed that organic matter content as measured by color chart in 14 soil samples out of 16 matches well with the organic matter content measured by wet oxidation method representing an accuracy of 87.5%. However, further fine-tuning is necessary for the developed color chart with extensive validation using a large set of soil samples covering all AEZ, in wide ranges of soil types, management, and soil texture before recommendation to the farmers.