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Soil Aggregate Stability in RangelandsPowerPoint Presentation

Soil Aggregate Stability in Rangelands

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### Soil Aggregate Stability in Rangelands

Leonard Cratic

Mentor: Jeff Stone

USDA-ARS SWRC

UNIVERSITY OF

Introduction

Erosion is a process which impacts the sustainability of rangelands.

There is a need to develop simple tools to evaluate sustainability of rangelands.

Problem Statement

Two methods being used to estimate runoff ratio and erosion:

Direct measurement

- Rainfall simulation
- Expensive and time consuming
Indirect measurement

- Slake testing
- Measures soil aggregate stability
- Quick and inexpensive

Objectives

Assess the influence of plant cover on soil slake.

Determine whether correlations exist between soil slake and runoff and erosion.

Methods

Rainfall simulation

- Rainfall is applied to a 2x6 meter plot and runoff and erosion is measured.
- Four plots per site

Soil Aggregate Stability

Measures how well a soil ped retains its structure in water

- Soil stability kit
- 18 samples per plot
- Presence of plants noted and soil samples ranked 1-6 (unstable-stable)

Study Areas 5 sites evaluated in Southeastern Arizona From observations

Loamy Uplands ecological site

- Soil-vegetation association

- ER2 and KREE are most stable
- ER4G and ER4S are moderately stable
- ER3 is least stable

Analysis

Slake evaluated using a t-test

- Under and outside canopy
- Among study sites
Regression analysis (slake vs. rainfall simulation)

- Slake vs. runoff ratio
- Runoff ratio = runoff / precip.

- Slake vs. sediment yield
- Sediment yield = sy / precip. / slope

Under vs. Outside Canopy

Means are significantly different if letters are different

Slake Among Sites

Means are significantly different if letters are different

Conclusions

- Soil that was protected by canopy cover had more stable aggregates.
- Significant differences in slake were between ER4S, ER2 and KREE.
- No correlation was found between slake and runoff ratio.
- A negative correlation was found between slake and sediment yield.
- The addition of more data will help to strengthen the validity of using slake testing for erosion assessment.

Acknowledgements

Susan Brew

Jeff Stone

Chandra Holifield Collins

Rae Gomez-Pond

Jared Buono

Jonathan Krattickk Jakucki

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