Modified rapid method for textural analysis of saline and alkaline soils.

Abstract

In most soil testing laboratories, textural analysis is performed by the pipette method (PM) or by hydrometer. Objectives of this study were (i) to evaluate simplified methods that can be used for soils of various textures, and (ii) to modify a rapid method for reliable and accurate textural analysis of saline and alkaline soils. One hundred soils were collected from different agro-ecological regions of India. Coefficients of variation for sand, silt, and clay of soil samples by the rapid method varied across a range of 0 to 5% with a mean value <3% for all soils. Absolute differences between the PM and the rapid method for sand, silt, and clay fractions ranged from −1.8 to 1.7, −1.8 to 5.3, and −2.9 to 1.8%, with averages across the sites of −0.04, 2.92, and −6.52%, respectively. Among various methods, regression analysis between the rapid and pipette methods produced the highest coefficient of determination (r 2) values of 0.9989, 0.9927, and 0.9930 for sand, silt, and clay fractions, respectively. A rapid method with modified sodium hexametaphosphate concentrations and soil shaking periods produced mean, standard error, and standard deviation values very close to the PM, with r 2 values >0.99 with small intercepts <0.5, <0.3, and <0.7 for saline, saline–alkaline, and alkaline soils, respectively. The rapid method with proposed modifications provides the most accurate and fast estimation of texture for saline–alkaline soils.