|WACHA, K - University Of Iowa|
|PAPANICOLAOU, A - University Of Tennessee|
|GIANNOPOULOS, CHRISTOS - University Of Tennessee|
|ABBAN, B - University Of Tennessee|
|WILSON, C - University Of Tennessee|
|ZHOU, SHENGNAN - University Of Tennessee|
|FILLEY, T - Purdue University|
|HOU, T - Purdue University|
Submitted to: Geosciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2018
Publication Date: 12/11/2018
Citation: Wacha, K.M., Papanicolaou, A.N.T, Giannopoulos, C.P., Abban, B.K., Wilson, C.G., Zhou, S., Hatfield, J.L., Filley, T.R., Hou, T. 2018. The role of hydraulic connectivity and management on soil aggregate size and stability in the Clear Creek Watershed, Iowa. Geosciences. 8(12). https://doi.org/10.3390/geosciences8120470.
Interpretive Summary: Soil management practices affect the ability of the soil to respond to different stresses and degradation of soils is affected by how aggressively we till the soil. This study was implemented to determine the distribution of soil aggregates along a transect within an agricultural landscape. This type of analysis is rarely conducted in agricultural settings to determine the differences among different positions on a slope and the effect of management practices. The more aggressive the tillage with reduced conservation practices, the smaller the aggregate size and the more susceptible the soil to runoff and movement of these soil particles down the slope. In contrast, soils maintained under some degree of conservation practices have larger aggregates and reduced chance of soil particle movement. Our ability to understand the dynamics of soil aggregates under different management practices provides a foundation for improved soil management practices. This information is valuable to soil scientists and natural resource conservation personnel to understand how soil aggregates respond to management changes.
Technical Abstract: This study provides a systematic examination of the role of management practices on aggregate dynamics at the hillslope scale in intensively managed agricultural landscapes. The focus is on the small macroaggregates (0.25-2.0mm) as they best reflect the role of management practices on size distribution and stability. A modified definition for determining the dry mean weight diameter (DMWD) is presented and used a priori to determining wet aggregate stability with the use of a calibrated rainfall simulator for small macroaggregate samples. Soil samples were collected along the downslope flow pathways of representative hillslopes within conservation and conventionally managed fields as well as a restored prairie. Overall, this study offers some valuable insight into the controls that management, landscape processes, and raindrop impact have on aggregate dynamics. Increased tillage perturbations were found to preferentially skew aggregate size distributions towards finer fractions as well as decrease stability. Soils from conservation sites were found to have comparable stability values as restored grassland sites, as the conservation measures allow more time for the aggregates to grow and stabilize. Failure to consider the breakdown, mobilization and transport of soil aggregates in process based models could produce significant errors in redistribution estimates at the hillslope scale, which could then propagate to larger scales. The stability of aggregates due to raindrop and water impact may also provide some key insight on available size fractions preferentially entrained in various flow conditions.