MIXTURES OF COAL ASH AND COMPOST AS SUBSTRATES FOR HIGHBUSH BLUEBERRY

Authors: Black, Brent; ZIMMERMAN, RICHARD - RETIRED USDA FRUIT LAB

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2002
Publication Date: N/A
Citation: N/A

Interpretive Summary: Highbush blueberry (Vaccinium corymbosum L.) plants require low-pH, sandy soils containing high levels of organic matter. These soil requirements limit the number of suitable sites for commercial production to a few specific geographic regions, and have made it difficult to grow blueberries on diversified direct-market oriented small farms. We tested bottom ash from a coal-fired power plant and two composts as components of soil-free substrates for growing highbush blueberry (Vaccinium corymbosum L.). These substrates were compared to a typical commercial blueberry soil (Berryland sand) and an upland soil not suitable for highbush blueberry (Manor clay loam). The pH of all treatments was adjusted to 4.5 with sulfur at the beginning of the experiment. Plants of 'Bluecrop' and 'Sierra' were grown in pots containing the treatment media for four seasons, and growth, yield, fruit size, and elemental content of leaves and fruit were measured. Growing highbush blueberry in coal ash or composted biosolids had no detrimental effect on the elemental content of leaves or fruit. Growth and yield of plants in ash/compost mixes equaled or exceeded that of the typical blueberry soil. Coal ash is freely available in regions which utilize coal-fired electrical generators, and many farms are now producing their own compost. This research will be of value to small-scale diversified fruit producers interested in cropping highbush blueberry on sites which lack suitable soil.

Technical Abstract: Bottom ash from a coal-fired power plant and two composts were tested as components of soil-free media and as soil amendments for growing highbush blueberry (Vaccinium corymbosum L.). Combinations of ash and compost were compared to Berryland sand, and Manor clay loam, and compost amended Manor clay loam. The pH of all treatment media was adjusted to 4.5 with sulfur at the beginning of the experiment. In 1997, plants of 'Bluecrop' and 'Sierra' were planted in 15 dm3 pots containing the pH-adjusted treatment media. The first substantial crop was harvested in 1999. At the end of the 1999 season, one half of the plants were destructively harvested to analyze stem and root growth. The remaining plants were cropped again in 2000. Yield and fruit size data were collected in both seasons, and leaf and fruit samples were collected in 1999 and analyzed for elemental content. The presence of coal ash or composted biosolids in the media had no detrimental effect on leaf or fruit elemental content. Total growth and yield of both cultivars was reduced in clay loam soil compared to Berryland sand, whereas growth and yield of plants in coal ash/compost was similar to or exceeded that of plants in Berryland sand.