Submitted to: Journal of Natural Resources and Life Sciences Education
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2010
Publication Date: 4/1/2011
Publication URL: http://handle.nal.usda.gov/10113/53709
Citation: Nichols, K.A., and Samson-Liebig, S. 2011. An inexpensive and simple method to demonstrate soil water and nutrient flow. Journal of Natural Resources and Life Sciences Education. 40:51-57. Interpretive Summary: One of the greatest limitations to crop production is the lack of adequate water amounts. Soil functions such as water infiltration, water holding capacity, water retention, gas exchange, and nutrient cycling, assist in water movement and availability to plants. Demonstrations are often conducted to assist non-technical audiences in visualizing the interrelationships between soil physics, chemistry, and biology which allow soil to function. This study was designed to develop and test methods for demonstrating soil quality parameters to non-technical audiences in the classroom and field. Soil samples from different treatments are compared by placing soil in a container with a porous bottom and measuring the rate of water flow into the soil, the amount of water retained in the soil samples, and potential nutrient loss from the soil due to water movement. Tests of the accuracy and precision of these methods showed them to be adequate for demonstrating infiltration, water retention, and potential nutrient loss.
Technical Abstract: Soil quality, soil health, and soil sustainability are concepts which are being widely used but are difficult to define and illustrate especially to a non-technical audience in the field or classroom. The USDA-NRCS/ARS Soil Quality Test Kit, as well as other commercially-available kits, contains many useful and simple tests for measuring soil quality parameters and comparing agricultural management systems. However, these kits are costly, require specialized equipment or supplies, or are not flexible enough to demonstrate soil health under a wide range of circumstances. In addition, methods to demonstrate water holding capacity and potential nutrient loss frequently are not measured in these kits. The objectives of this manuscript were to develop and test the accuracy and precision of methodologies to both qualitatively and quantitatively estimate water infiltration rates, water-holding capacity at saturation, and potential nutrient loss. Details for how to assemble the appropriate supplies and conduct the measurements are provided. The results for testing the methods on a number of experimental sites are presented and compared to a laboratory measurement of a Whole Soil Stability Index. The quantitative measurements showed infiltration rate increased with a reduction in soil disturbance and an increase in plant cover. Water-holding capacity followed a similar trend while nitrate-N loss was highest in soil with higher synthetic fertilizer inputs, less plant cover, and more soil disturbance. These trends followed expected results based on treatment or management’s impact on soil health.