Evaluation of Water–Air Balance of Various Substrates on Begonia Growth

Abstract

The water–air balance of four soilless substrates: 75% sphagnum peat–25% perlite (Ps 75 :P 25 ), 50% sphagnum peat–50% perlite (Ps 50 :P 50 ), 50% coir–50% perlite (C 50 :P 50 ), and a fortified substrate with 60% sphagnum peat–30% black peat–10% perlite (Ps 60 :Pb 30 :P 10 ) (in a volumetric proportion) was investigated under two different irrigation methods (drip and sub-irrigation), and its effect on the growth of Begonia ×elatior ‘The President’ was studied. The bulk density, particle size distribution, and water retention curve of the substrates were determined. Furthermore, the water profiles, oxygen (Ο 2 ) concentration, and Ο 2 diffusion rate of all substrates were determined during a 16-week cultivation period. Plant height, flower production, and both shoot and root dry weights as well as percent growth increase of plants were measured at the end of the experiment. The substrate water profiles showed that the water content was greater and air content was less in substrates of pots irrigated with drip irrigation than with sub-irrigation. The O 2 concentration in all substrates irrespective of the irrigation method was high. The O 2 diffusion rate values of sub-irrigated substrates were greater than those drip-irrigated, and Ps 60 :Pb 30 :P 10 showed the greatest values. Shoot and root dry weights and percent growth increase of drip-irrigated plants were greater than that of sub-irrigated plants.