Growth, physiology, and leachate losses inPicea glaucaseedlings (1+0) grown in air-slit containers under different irrigation regimes

Abstract

In production tunnels, time domain reflectometry (TDR) was used to manage irrigation and leaching by controlling water content in the rhizosphere of air-slit containerized white spruce (Picea glauca (Moench) Voss) seedlings (1+0). Seedlings were exposed to four irrigation regimes (v/v: IR-60%, IR-45%, IR-30%, and IR-15%) during the first growing season to assess IR effects on growth, gas exchange, nutrient uptake, carbohydrates, root architecture, and leaching. In the province of Quebec, seedling producers generally maintain a high substrate water content (>50%, v/v) during all growth phases. The accuracy and feasibility of using TDR to decrease irrigation without affecting the material attributes of the seedlings at the end of the first growing season was confirmed. However, seedlings grown under IR-15% had significantly lower height, root collar diameter, shoot and root dry masses, root surface, root length, net photosynthesis, and nutrient contents than seedlings grown under IR-30%, IR-45%, and IR-60%. In comparison with IR-30% and IR-45%, the application of IR-60% produced no increase in shoot or root growth, mineral nutrition, and carbohydrates. Seedlings grown under IR-15%, IR-30%, and IR-45% used approximately 28, 37, and 46%, respectively, of the amount of water applied under IR-60%. Nutrient losses including anions and cations under IR-60% were higher in comparison with the other IRs. Maintaining a water content in the rhizosphere that changes with the stage of seedling development is suggested to optimize growth and to avoid excess irrigation and leaching.