Korean Journal of Soil Science and Fertilizer ISSN:0367-6315(Print) 2288-2162(Online) 한국토양비료학회 학회지

The estimation of water retention for perlite particles, which are used as growth media need to set up for proper water management strategy due to uncertain available water proportion during growth period of vegetable crops in a greenhouse. The water retention curves (WRC) expressed as volumetric water content (θ_v) were constructed with five different sizes of the expanded perlite after fully saturating and packing the perlite in open-ended metal cubes at 11 levels of matric potentials from 0 to -1,500 kPa. The best fitted four parameter values (θ_s, θ_r, n, α) of the van Genuchten model (vG model) for the substrate samples were obtained using the Retention Curve Program (RETC) based on the values measured water content at the corresponding matric potentials. The particle size corresponding to 36.8 percentage by mass of particles was 0.80065 mm. The calculated uniformity coefficient and the coefficient of gradation for the perlite were 1.962 and 2.51 mm, respectively. Measured water contents at each matric potential increased with decreasing particle size of perlite while the difference of water content between saturation (θ_s) and residual state (θ_r) increased with increasing particle size. The mean R² for all sizes of the perlite particle was suitable to predict θ_v because the measured data points did not vary around the estimated regression line. Therefore, PTF performance based on van Genuchten (vG) equation using data set including perlite particle size can be applicable to estimate water retention in perlite particles.

Water retention curves measured at the water potential ranging from 0 to -1,500 kPa for five levels of particle size of expanded perlite.