Understanding and Addressing Weed Science Problems Using Soil Physics

Abstract

In the literature, few studies have successfully integrated principles and concepts of soil sciences (specifically soil physics) and weed science, where knowledge gaps and research questions involving both branches of science have not been addressed from an interdisciplinary perspective. The main objective of the present dissertation was to evaluate the use of principles and concepts of soil physics aiming to develop a more comprehensive view of weed related issues to better inform the decision-making process when designing weed management strategies. A set of experiments was conducted to address three general objectives: 1) to assess the role of water potential on seed germination through comparisons among osmotic solutions and mineral soils, 2) to investigate the potential lateral movement of solutes in soils with textural anisotropy, using a field trial and numerical modeling approach, and 3) to characterize the potential carryover risk of two residual herbicides and its further effects on carinata (Brassica carinata A. Braun) establishment in two different soils of North Carolina. When comparing total seed germination of four plant species using soils or polyethylene glycol (PEG) as germination substrate, dramatic differences in seed germination were observed, even when seeds were submitted to the same water potential. These results indicated that PEG did not reproduce accurately how the edaphic environment supplies water to seeds during germination. Furthermore, when exploring the role of soil unsaturated hydraulic conductivity (Kh) on seed germination, it was shown that the variability observed among soils and water potentials was better explained by Kh than PEG–generated osmotic potentials. A field study provided empirical evidence for lateral movement of a conservative tracer (Br-), which moved along the surface horizon (Ap) following the soil slope. This movement was also modeled using HYDRUS 2D/3D, which allowed to visualize accurately...