Abstract
Infiltration rate (IR) has been commonly used as a metric to evaluate soil quality and health. For the USDA Soil Quality Test Kit, a 15 cm (6 in) diameter cylinder is used to measure IR with 444 cm3 (equivalent to 2.54 cm [1 in]) of water while other standard IR procedures require substantially larger volumes of water. The general objective of this study was to compare different methods for IR measurement. Using three replications, IR measurements were conducted along a 9 m (27 ft) long transect in two different soil types by the double-ring infiltrometer (DRI) using 25 and 50 cm (10 and 20 in, respectively) cylinders, single-ring infiltrometer (SRI) using 25 and 50 cm cylinders, Cornell sprinkle infiltrometer (CSI) using a 24.1 cm (9.5 in) cylinder, the USDA recommended procedure using a 15 cm diameter cylinder (hereafter referred to as USDA-15 method), and a modified USDA method using a 24.1 cm diameter cylinder. Although the USDA-15 method is simple and requires a small amount of water, the procedure does not offer an accurate estimate of the soil infiltration potential due to high variability among replications and significant reduction in IR during early stages of water entry into the soil. The CSI procedure was reproducible, but it is more cumbersome to perform than other methods. The DRI, SRI, and CSI methods required a much greater volume of water than the USDA-15 method but produced results that are more consistent. The most consistent results were obtained by the CSI and DRI methods. The modified USDA method results were similar to the SRI method and were an improvement over the original USDA-15 method. For assessing soil health, additional investigations should be conducted to evaluate a modified version of the USDA procedure using a larger cylinder.
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