Field soil aggregate stability kit for soil quality and rangeland health evaluations

Soil aggregate stability is widely recognized as a key indicator of soil qu ality and rangeland health. However, few standard methods exist for quantif ying soil stability in the field. A stability kit is described which can be inexpensively and easily assembled with minimal tools. It permits up to Is samples to be evaluated in less than 10 min and eliminates the need for tr ansportation, minimizing damage to soil structure. The kit consists of two 21 x 10.5 x 3.5 cm plastic boxes divided into eighteen 3.5 X 3.5 cm section s, eighteen 2.5-cm diameter sieves with 1.5-mm distance openings and a smal l spatula used for soil sampling. Soil samples are rated on a scale from on e to six based on a combination of ocular observations of slaking during th e first 5 min following immersion in distilled water, and the percent remai ning on a 1.5-mm sieve after five dipping cycles at the end of the 5-min pe riod. A laboratory comparison yielded a correlation between the stability c lass and percent aggregate stability based on oven dry weight remaining aft er treatment using a mechanical sieve. We have applied the method in a wide variety of agricultural and natural ecosystems throughout western North Am erica, including northern Mexico, and have found that it is highly sensitiv e to differences in management and plant community composition. Although th e field kit cannot replace the careful laboratory-based measurements of soi l aggregate stability, it can clearly provide valuable information when the se more intensive procedures are not possible. (C) 2001 Elsevier Science B, V. All rights reserved.