BORON DISTRIBUTION AND THE EFFECT OF LIME ON BORON UPTAKE BY PANSY, PETUNIA AND GERBERA PLANTS

Abstract

Reports of boron (B) deficiency have become more prevalent in pansy (Viola ×wittrockiana), petunia (Petunia ×hybrida), and gerbera (Gerbera jamesonii) plug production. When symptoms are observed in production the presence and severity of symptoms have no obvious pattern; symptomatic plants can be located adjacent to asymptomatic plants in the same plug flat. The availability of B in the soil decreases as soil pH increases. ‘Yellow Dynamite’ pansy, ‘White Storm’ petunia, and ‘Festival Apricot’ gerbera seedlings were grown in a peat:perlite substrate that was amended with pulverized dolomitic limestone at a rate of 3,560, 4,746, 5,933, or 11,866 g/m3. As the rate of lime incorporated into the substrate increased so did soil pH and shoot tissue concentrations of Ca while shoot tissue concentrations of B decreased. Many commercially available germination substrates are amended with macro- and micro-nutrient fertilizers as fertilizer granules. Relatively small amounts of each element are incorporated into the substrate and uneven mixing could result in varying amounts of nutrients in individual cells of a plug flat. This variability could lead to nutrient deficiencies early in the crop cycle. Six commercially available germination substrates were used to fill plug flats and individual cells were sampled and analyzed for B concentrations. Of the substrates tested, there was no variation in B concentration from cell to cell.