S06 - Session P16 - Root growth and evolution of substrates physical properties according to irrigation strategies

Authors: Jean-Charles Michel *

Supported by many French substrates' companies (Aquiland, Biolandes Pin Decor, Dumona, Fertil, Florentaise, Floragard, IfTech, Klasmann-Deilmann, Agaris, Lesaffre Plant Care and Premier Tech Horticulture France), the 'Ecol'eau Terreau' research project aimed to improve the water use efficiency for pot plants, by considering the evolution of physical properties of substrates according to irrigation strategies and their consequences in terms of root growth. Many experiments were carried out in greenhouses, using different substrates (peats, barks, wood fiber, coir and mixes), plants (rose, ipomoea, onion), and irrigation strategies (water potential maintained at -1 kPa, irrigation triggered when water potential reached -10 kPa or -30 kPa). For each experiment, root and shoot biomass, air and water retention properties, hydraulic conductivity, relative gas diffusivity and wettability were evaluated at the beginning and at the end of the experiment. Whatever the substrate tested, results showed quite similar evolutions of physical properties depending on irrigation strategies and root development. However, relevant parameters explaining root performance were depending on the irrigation strategies: results highlighted the importance for wettability in case of restrictive irrigation (-30 kPa), whereas water and moreover air content and flow seemed to be relevant for predicting root content for non-limiting irrigations (-1 kPa). From these results, mechanisms explaining the evolution of substrates physical properties according to both irrigation strategies and root growth have been described. That thereby provide opportunities for the Substrates' industry to develop more efficient substrates and better advices to the end-users.