Nursery Floor Affects Containerized Plant Growth

Rooted stem cuttings of ‘Skogholm’ cotoneaster (Cotoneaster dammeri ‘Skogholm’) potted into 14.2 liter (#5) containers in a pine bark: sand substrate were used to determine the effects of the nursery floor on plant growth, water use efficiency, substrate and plant canopy temperature, winter protection, and mineral nutrient efficacy. Four nursery floors were evaluated: black plastic, black ground fabric over black plastic, white plastic, and gravel from May 10, 2001, to April 23, 2002. Plants grown on gravel or ground fabric/black plastic had greater top and root dry weights compared to plants grown on white plastic. Water use efficiency was similar across all nursery floors, requiring an average 391 ml (13.2 oz) of water to produce a gram (0.04 oz) of plant material. Net photosynthetic rates of plants grown on black plastic, gravel, or ground fabric/black plastic were significantly greater than cotoneaster grown on white plastic. Plants grown on white plastic had significantly higher plant canopy [1 to 2C (1.8 to 3.6F)] and substrate temperatures [1 to 4C (1.8 to 7.2F)] daily from 1000 HR to 2000 HR throughout the summer months compared to all other nursery floors. Plant canopy and substrate temperatures were unaffected by the nursery floor during the winter months. Nitrogen efficiency was 42% on ground fabric/black plastic, 40% on gravel, 37% on black plastic and 33% on white plastic. Phosphorus efficiency was 53% on gravel, 52% on ground fabric/black plastic, 49% on black plastic and 43% on white plastic.