PRELIMINARY INVESTIGATIONS ON AN ARTIFICIAL SOIL AGGREGATE USED IN BOTANICAL EXPERIMENTS: INITIAL GRAIN SIZE, REFLECTIVE SPECTROSCOPY, AND TRANSMISSION ELECTRON MICROSCOPY RESULTS

Botany is an important area of environmental sciences and is crucial to science, medicine, and agriculture. Botany is vital in economic productivity because it is involved in the study of crops and the ideal growing techniques that help farmers increase crop yield. Not only does the application of botany in agriculture increase economic profit, but it is also becoming increasingly more necessary from a sustainability perspective. As our soil becomes depleted of nutrients worldwide, we must become more innovative with our agricultural techniques to ensure enough food for the growing population. One aspect of experimental botany that can be greatly expanded is detailed studies of synthetic aggregate commonly used. Different types of aggregates can benefit experimental or engineered botanical systems in different environments in many ways.

Caliper measurements of individual particles indicate that the dimensions of aggregate are modified by washing with unwashed aggregate having mean short axis length of 1.76 mm and mean long axis length of 4.33 mm and a 2.65 aspect ratio. Washed aggregate has mean short axis length of 1.68 mm and mean long axis length of 3.32 mm and a 2.12 aspect ratio, likely resulting in higher porosity for washed aggregate and lower and more flat packed porosity for dry aggregate. Reflective spectra of dry and wet samples were obtained and are dominated by hydroxyl features and oxidized iron features. Spectra of samples are heavily impacted by addition of water content, indicating that reflective spectra or hyperspectral imaging could be used to monitor surface moisture content in experiments. Initial transmission electron microscopy investigation on particles indicates that there are two dominant clay-sized particle types, a vermiculitic phyllosilicate and amorphous silica. Vermiculitic particles are characterized by compositions having Na, K, Mg, Al, Si, Ti, Fe and minor Mn and electron diffraction shows some turbostratic stacking. Amorphous silica particles are dominated by Si with minor Al, Fe and K and have few or no diffraction spots. Further investigations on other properties and how the washing and mechanical treatments impact cation exchange, the pore environments, and ultimately rhizosphere ecology are warranted.