mortiz085

President Rodrigo R. Duterte emphasized the conduct of soil analysis in the country during his first State of the Nation Address (SONA) on July 15, 2016. He said that “we shall also conduct a nationwide soil analysis to determine areas most suitable for rice farming to optimize production with the use of effective soil rehabilitation and fertilization.” As an effect of this presidential pronouncement, many people including professionals from various academic fields have been wondering what soil analysis is. Several readers of this blog suggested that I write about this topic hence, this article. Soil analysis refers to the measurement of soil physical, chemical, and biological properties. It is done, depending on the type of soil analysis, for the following purposes: 1) to evaluate the origin and formation of the soil; 2) to assess the level of contamination of the soil; 3) to characterize the soil as a habitat of soil organisms; 4) to assess the soil fertility status; and 5) to evalu...

Students of soil science are taught that to determine the amount of soil organic matter, soil organic carbon is measured usually by wet oxidation using potassium dichromate (called Walkley-Black method) or in well-equipped laboratories, using CN analyser and then multiplied by a conversion factor of 1.72 or 1.724. Most textbooks and laboratory manuals do not explain how this factor was obtained, so students generally accept the value without any question just like they do with other constants used in natural sciences.  Origin of the conversion factor The conversion factor has a very long history and has practically survived the test of time and modern analytical methods. It is about 150 years old. It was based on studies in the 1820s by the famous agricultural chemist, Carl Sprengel of Goettingen University, that organic matter contains 58 percent carbon. But it was another leading agricultural chemistry pioneer, Emil Wolff from Hohenheim, who introduced the value of 1.724 in 1864....

Organic matter (OM) is the most important cementing agent of soil particles. Soils containing high amount of OM (like the limestone soil from Leyte in the picture below) generally have good aggregation (i.e. the sand, silt and clay particles are glued together by the OM). Removal of OM using chemical reagents is thus an important pretreatment in textural or particle size analysis as well as in the evaluation of soil mineralogy, cation exchange capacity, and surface area. Soil in Leyte having a dark surface horizon due to OM  Hydrogen peroxide (H2O2) which was first used in 1923 by G.W. Robinson to destroy soil organic matter, is the most widely used chemical reagent for removing OM in soil laboratories worldwide. However, there have been some scientific reports indicating that it may not be a good reagent for that purpose due to some unwanted effects on the mineral soil particles. In the Philippines, it is not also easy to procure large volumes of hydrogen peroxide since it require...