Civil Engineering June 2022 | Vol 30 No 5

58 June 2022 Civil Engineering How does one save water? A quick Google search suggests the typical solutions: checking plumbing for leaks, taking short showers and watering your garden at night. These solutions, though beneficial, are not maximising the time old saying, “every drop counts”. So, how do ordinary individuals maximise their water saving capacity? A dirt simple solution. Improving the water holding capacity of soils is not commonly thought of as a way to save water. As South Africa is considered to be the 30 th driest country in the world and experiences regular droughts, undoubtedly aggravated by global climate change, finding methods of saving water is vital. Soils are important for all life as they store the nutrients and water necessary for plant life to grow and therefore facilitate food production. The ability of a soil to retain or hold water is closely linked to the ability of a soil to support plant growth. By improving the water holding capacity (how much water a given soil mass can hold) of a soil, more water is available for plants to use. The effect of this is that gardens and/or farms can reduce their irrigation requirements and subsequently save water. BACKGROUND Vermicompost is a form of organic ferti- liser made from earthworm castings. Food and garden waste is fed to and digested by earthworms before being excreted in the form of nutrient rich earthworm castings. These castings are then used as a fertiliser to improve the biological and physical characteristics of a soil, particularly its water holding capacity. Vermicompost improves the structure of the soil by filling in the porous spaces within the soil. This leads to more water being absorbed by the organic matter in- stead of escaping as run-off. In some cases, the use of vermicompost in sandy soils can reduce water requirements by more than 30%. This has the potential to create significant water savings, particularly in South Africa where more than 15% (18 mil- lion hectares) of the total land area consists of sandy soils and 2.6 million hectares of this land area is currently farmland. AIMS AND OBJECTIVES The aim of the experiment was to deter- mine the effect of different concentrations of vermicompost on the water holding capacity of loam, sandy and clay soils. The effect of vermicompost was tested against more well know and popular traditional composts. PROJECT DESCRIPTION The experiment focused on the three main soil types, namely loam, sandy and clay soils. 100 g samples of each soil type were prepared with 0% (the control mix), 5% and 10% concentrations of vermicompost or compost. These samples were placed in individual funnels, saturated with water and allowed to stand for 2 hours in a closed laboratory. This is known as the percolation method. After 2 hours the samples were weighed and the results were used to calculate the changes in water holding capacity (WHC) using the following equations: I P Showdown The effect of vermicompost on the water holding capacities of soil Ashley Randall Civil engineering graduate University of the Witwatersrand ashimegrandall@gmail.com linkedin.com/in/ashley-randall-9097931b2 LiamMacgregor Civil engineering graduate University of the Witwatersrand macgregorliam8@gmail.com linkedin.com/in/liam-macgregor Each year SAICE joins forces with South Africa’s leading universities to award civil engineering students for their research efforts. The following article outlines the research undertaken by the 2022 SAICE National IP Showdown winners. Ashley Randall and Liam Macgregor, winners of the 2022 SAICE National IP Showdown