The impact of tillage row orientation on physical and chemical sediment enrichment

Authors: WACHA, KENNETH - Orise Fellow; PAPANICOLAOU, THANOS - University Of Tennessee; ABBAN, BENJAMIN - University Of Tennessee; WILSON, CHRISTOPHER - University Of Tennessee; GIANNOPOULOS, CHRISTOS - University Of Tennessee; HOU, TINGYU - Purdue University; FILLEY, TIMOTHY - Purdue University; Hatfield, Jerry

Submitted to: Agrosystems, Geosciences & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2019
Publication Date: 12/11/2019
Citation: Wacha, K.M., Papanicolaou, A.N.T., Abban, B.K., Wilson, C.G., Giannopoulos, C.P., Hou, T., Filley, T.R., Hatfield, J.L. 2019. The impact of tillage row orientation on physical and chemical sediment enrichment. Agrosystems, Geosciences & Environment. 3(1). https://doi.org/10.1002/agg2.20007.
DOI: https://doi.org/10.1002/agg2.20007

Interpretive Summary: This manuscript investigates the role of tillage orientation and roughness on runoff and sediment fluxes in experimental plots using simulated rainfall. We found the orientation of cropping rows to dramatically impact discharge rates and the size distribution of sediment fractions transported. Next, we discuss the relation between physical and chemical based methods to quantify the enrichment of the sediment, which can be used in quantifying hydrologic-driven soil organic carbon fluxes. Sorting and selectivity of sediment fractions was found to be related to physical enrichment, while chemical enrichment was the consequence of physical enrichment, in that finer grain particles better adsorbed nutrients like soil organic carbon. We present time series of steady and unsteady enrichment values using both methods and finish showing a positive relation between the two methods. This can have a great impact on future modeling frameworks trying to simulate soil carbon redistribution and improve soil carbon budgets, by accounting for the role tillage orientation plays on sediment fluxes and enrichment.

Technical Abstract: This study aimed to understand better how tillage row orientation with respect to the dominant flow-pathway along a hillslope impacts runoff and the different size fractions of the transported sediment. Experimental plots were constructed in contour ridge till (CRT) and parallel ridge till (PRT) sites to monitor runoff and sediment fluxes. The particle size fractions of the sediment, along with organic carbon and nitrogen contents were measured to quantify physical and chemical enrichment ratios, respectively, for the two tillage orientations. In the CRT plot, tillage produced large oriented roughness elements along the contours, which acted as little check dams, while in the PRT site, the roughness elements helped confine and concentrate the runoff. In the CRT, the “check dams” resulted in a runoff coefficient of 0.03, while in the PRT, the flow confinement between rows produced a runoff coefficient of 0.82. Moreover, the erosion rates at the CRT site were 97% less than those in the PRT plot. The CRT site, with large contours, produced finer sediment fractions due to the selective sorting in ponded furrows. More aggregate sediment fractions were present in the PRT site, which was dominated by rill erosion. Physical enrichment revealed selective entrainment of finer sediment particles during erosion. Since finer-grain particles have higher specific surface areas, they can attach relatively more soil organic carbon (SOC) resulting in a chemical enrichment. Physical and chemical enrichment methods were found to be in good agreement. These findings suggest transport models that can simulate size fraction updates to the soil active layer can be used to estimate SOC redistribution and hence more accurate carbon budgets.