The effect of increasing organic matter in soil on water retention (WHC) and percolation for landscaping purposes

Abstract

This comprehensive report examines the effects of increasing organic matter (OM) / compost content on water retention/water holding capacity (WHC) and percolation in three types of soils from Malta: a silty to silt loam Luvisol (Ħamri), a clay-rich Regosol (Tafli), and a sand-rich loam Calcisol (Bajjad). A series of laboratory experiments was performed on a representative sample of these soils using OM (compost) additions at 0 %, 3 %, and 6 % by mass. Each mixture was analysed for pH, conductivity, water holding capacity (WHC), and percolation rate, with all procedures carried out in triplicate to ensure accuracy. The data were analysed statistically to determine how increasing organic matter affected soil water retention and drainage properties. The results show that the addition of OM significantly influences WHC, and the soil type strongly impacts percolation behaviour, with OM level affecting percolation at early stages. The most notable improvements were seen in the Calcisol, which exhibits moderate percolation rates, with the most pronounced changes occurring at 3 % OM.