SODIUM-CARBONATE INHIBITS EMERGENCE AND GROWTH OF GREENHOUSE-GROWN WHITE SPRUCE

Conifers are extremely sensitive to salinity and in western North Amer ica irrigation waters may contain appreciable amounts of soluble salts . The objective of this study was to assess the effect of salinity of Na-enriched irrigation water (as sodium carbonate [Na2CO3]) on the eme rgence and growth of white spruce (Picea glauca [Moench] Voss). An exp eriment using a randomized complete block design with four replicates and five salt treatments to give solution electrical conductivity (EC) of 0, 0.5, 1.0, 1.7 and 3.1 dS m(-1) was established in a greenhouse. White spruce seedlings were grown in styroblock growing trays using a sphagnum peat-perlite growing medium. Seedlings were fertilized twice a week following a fertilizer regime of a commercial tree nursery. Gr owth measurements, chemical analysis of the foliage, roots and growing medium were completed after 12 wk. Emergence was reduced by about 8% and growth was only 50% in the 0.5 dS m(-1) (92.9 mg Na+ L(-1) as Na2C O3) treatment compared with the control. Each treatment with successiv ely higher EC resulted in a further decrease in the emergence and grow th parameters. Excess internal Na+ concentration, water deficit result ing from high EC in soil solutions, and high pH of the growing medium were possible causes of the growth reduction. Nutrient concentrations other than Na did not differ among treatments except in the highest sa lt treatment. The presence of Na+ with CO32- as the companion anion at concentrations as low as 100 mg L(-1) with an EC of 0.5 dS m(-1) coul d potentially result in reduced emergence and growth of white spruce u nder greenhouse conditions.