Аннотация:Abstract A simple modification of the Day (1965) hydrometer method is suggested for routine textural analysis. The simplified method requires no calibration, graphs or tables and uses a weighted average of the 1.5‐hour and 24‐hour readings to determine the 2µm clay fraction. The relationship is: urn:x-wiley:03615995:saj2sssaj197903615995004300050038x:equation:saj2sssaj197903615995004300050038x-math-0001 where P 2µm = summation percentage for the 2µm clay fraction. P 24 , P 1.5 = summation percentage for settling time of 24 hour and 1.5 hour, respectively. K = weighting factor, used to approximate the actual relation of the summation percentage curve over the clay percentage range of interest. This equation was found to be satisfactory in the range of 5% ⩽ P 2µm ⩽60% by weight for over 70 North Dakota soil and subsoil materials when K =0.876. Sensitivity analyses were performed for the Day, Bouyoucos, and the Simplified Day hydrometer methods to determine which of several measured parameters contribute to the greatest possible error; hence which parameters should be controlled with the greatest precision. The hydrometer scale reading error contributes more error than any other single parameter.
