COMPARATIVE EVALUATION OF LABORATORY PROCEDURES FOR THE DETERMINATION OF TOTAL NITROGEN, ORGANIC CARBON AND PH IN A CALCAREOUS SOIL
Abstract
Laboratory analyses are important integral in soil chemistry and fertility management needed for evaluation and monitoring of overall nutrients, toxicant and productive status in soils. The variations in cost implication, variability in results from analytical procedures, time and rigor involved in carrying out total laboratory analyses demands proper selection of suitable procedures for soil test in the laboratory. This work therefore compared the suitability of two laboratory procedures each for total N, organic carbon and pH determinations in a calcareous soil.
The calcareous soil was from the Teaching and Research Farm of the Department of Horticulture Cape Peninsula University of Technology, South Africa. Eighteen soil samples earlier prepared and treated with appropriate chemical fertilizers with or without different biochar types for macro-nutrient leaching study were utilized for this trail. Laboratory procedures tested for each of the selected soil parameters were 1N KCl and distilled water procedures for soil pH determination, elemental analyzer and ignition procedures for soil organic carbon (SOC) determination and elemental analyzer and Macro-Kjeldahl procedures for total Nitrogen determination. Two sample T-test using GenStat statistical package was used to compare the two means from each of the procedure tested per soil parameter.
The Extraction of pH by distilled water produced higher mean value (8.45) across all the analyzed soil sample over the KCl extraction (7.80). The SOC determination by ignition method produced higher mean value (1.58%) across all the analyzed soil sample over the elemental procedure (1.41%). Total N extraction was higher under elemental procedure with drastically higher mean value of 0.55 over 0.06 mean value obtained from Macro-Kjeldahl procedures. Significance differences were observed in the two procedures tested for the determination of soil pH and total N, while the SOC determination by ignition and Elemental procedures were not significantly different from each other.
The two procedures used for the determination of each of total N and pH determination were, therefore, different from each other while those tested for SOC were similar in their organic carbon determination in the calcareous soil tested. Elemental and distilled water extraction procedures are therefore recommended for the determination of Total N and pH in the calcareous studied while both ignition and elemental procedures are suitable for SOC determination. Similar comparative evaluation of common laboratory procedures for soil parameter determination is recommended for southwestern Nigerian soils to minimize cost of analysis for profitable crop production.
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