Blueberries require an acidic soil that may be difficult to maintain with some of our high pH soils and with high pH irrigation water. Researchers in Chile and Spain have similar problems and also must produce organically, which can limit which acids you can use to acidify water. Researchers were also interested in whether silicon, a nutrient not technically required for plant growth, but often found to have beneficial effects, was helpful in blueberry production.
Scientists performed two separate fertigation experiments on ‘Ventura’ highbush blueberry grown in two media: coconut coir or sand. At the end of six months researchers measured plant height, shoot biomass, and leaf area.
- Silicon (Si) tests applied Si in the nutrient solution at four different doses from 0 to 1.2mM.
- The sand or coconut coir media on experimental plants were maintained at four pHs: 4.0, 4.75, 5.5, and 6.25, with either nitric or citric acid.
Silicon benefited blueberry growth in the coir, but made no difference in the sand. Plants were tallest (8% increase) and shoot dry and fresh biomass were increased by 21-25% with the highest level of silicon in coconut coir.
In the pH experiment, stem and leaf dry weight was 18-21% less with coir media pH of 6.25 than with the lower pHs. The optimum pH for vegetative growth was 4.0-5.5 regardless of acidification source used in the coconut coir. The optimum pH for growth was not conclusive in sand. Growth in media acidified with citric acid was similar to growth in media with nitric acid, indicating that citric acid can be a good organic acidification source.
Effect of pH and Silicon in the Fertigation Solution on Vegetative Growth of Blueberry Plants in Organic Agriculture. V.M. Gallegos-Cedillo, J.E. Alvaro, T. Capatos, T.L. Hachmann, G. Carrasco, and M. Urrestarazu. HortScience 53(10):1423-1428.