The effect of mineral fractions on physical and phosphorus-related chemical properties of peat-based substrates for pot plants

Physicochemical traits of peat-based pot substrates prepared from mixing of 20 or 40 vol.% of some different mineral fractions (sub. 1 to 7, subjected to decreasing amount of clay content of 66.1, 61.2, 49.7, 38.5, 26.0, 23.7 and 19.4%, respectively) with black peat were evaluated and then phosphorus uptake of poinsettia (Euphorbia pulcherima) simulated mechanistically as a case study pot plant. For preparation of substrate number 8, pure peat was mixed with 40 vol.% of the same mineral component as substrate number 6 (with 23.7% clay). Result revealed that adding different mineral fractions up to 40 vol.% to pure peat, water-holding capacity and total pore volume were reduced only by 11 and 15 vol.%, respectively. It was found that keeping the moisture content of peat-based substrates with 20 vol.% of mineral soils around 60%-70%, the optimum ventilation and enough free space of about 15%-25% will be provided around the root system. In addition, simulated P uptake did not change significantly with addition of 20 vol.% of different mineral components in peat-based substrates. As a result, P uptake mainly was dependent on the amount of plant available P level than different mineral fractions.