Episode 13: Chemistry Basics Part 2. Chemistry at Work in the Paddock and the Spray Tank

Send us Fan Mail Part 1 was atoms, charge and the periodic table. This episode puts that chemistry to work in places you already know: soil water, the fertiliser bag, and the spray tank. Leonie starts with a correction from last week: why potassium and calcium skip ahead on the electron shells, and why that is exactly where the transition metals (iron, manganese, zinc, copper) get their name. Then the reactions that actually show up on farm: - **Solutions:** almost nothing useful happens as a dry solid. It happens dissolved in water. - **Redox:** why a waterlogged pit goes grey and rusty orange, and why nitrogen can leave the paddock as a gas. - **Precipitation:** two soluble products meet, make an insoluble solid, and that is both blocked nozzles and phosphorus locked up with calcium, iron or aluminium. - **Chelation:** the “claw” on a fertiliser label (iron EDTA, zinc EDTA) that keeps a micronutrient soluble long enough for the plant to take it. - **Hard water and glyphosate:** calcium and magnesium tying up the herbicide before it reaches the weed. - **Alkaline hydrolysis:** why tank pH matters. - **Water repellence:**  waxy, non-polar coats on sand grains, and why the molarity of ethanol droplet test works. - **Gamma radiometrics:** potassium, uranium and thorium slowly changing under the paddock, and why that signal tracks clay in the top 40 cm. Salinity, heavy metals (including cadmium in some phosphate fertilisers), organic matter and acidity get a short map, then the series moves to pH next. If a section does not land, skip it. The next chemical-property episodes will keep using these ideas. Thanks to Williams Woolshed in Williams and Naked Bean Coffee Roasters in Albany. **Reference list** Chang, R., & Goldsby, K. A. (2016). *Chemistry* (12th ed.). McGraw-Hill Education. DeBano, L. F. (2000). The role of fire and soil heating on water repellency in wildland environments: A review. *Journal of Hydrology, 231–232*, 195–206. https://doi.org/10.1016/S0022-1694(00)00194-3 Geoscience Australia. (n.d.). *Radiometrics*. https://www.ga.gov.au/scientific-topics/disciplines/geophysics/radiometrics Grains Research and Development Corporation. (n.d.). Using ground-based EM and radiometrics to map soil amelioration. *GroundCover*. https://groundcover.grdc.com.au/agronomy/soil-and-nutrition/using-ground-based-em-and-radiometrics-to-map-soil-amelioration Kabata-Pendias, A. (2011). *Trace elements in soils and plants* (4th ed.). CRC Press. King, P. M. (1981). Comparison of methods for measuring severity of water repellence of sandy soils and assessment of some factors that affect its measurement. *Australian Journal of Soil Research, 19*(3), 275–285. https://doi.org/10.1071/SR9810275 Marschner, P. (Ed.). (2012). *Marschner's mineral nutrition of higher plants* (3rd ed.). Academic Press. McKenzie, N., Jacquier, D., Isbell, R., & Brown, K. (2004). *Australian soils and landscapes: An illustrated compendium*. CSIRO Publishing. **Connect with Leonie** Instagram: @agfromthegroundup Website: www.agriculturefromthegroundup.com.au