Role of Calcium in Citrus Production

Calcium nitrate and yield - Florida

Annual, cumulative use of calcium produces high yields. This was confirmed in a controlled, low pH environment experiment in Florida where high rates of calcium on its own increased tree growth rate and yield of navel oranges over an eight year period.

Calcium nitrate and ammonium nitrate

Calcium nitrate ensures higher yields compared to ammonium nitrate. Maximum yields in this fertigated trial (Valencia oranges, Brazil) were achieved with lower N rates applied by calcium nitrate. In a long-term series of trials, calcium nitrate has consistently proven to be the most effective form of fertilizer for producing high orange crop yields.

Yield on limed soils - valencia oranges, Florida

Regular use of soluble forms of calcium is also beneficial on high calcium carbonate soils or those that are regularly limed. After seven years of regular use, calcium boosted orange yields in USA trials by up to 56%. The nutrient also has a significant effect on reducing many fruit disorders.

Calcium and tree loss - oranges, Florida

Research in Florida across three citrus species, confirms that tree loss due to citrus blight (Fusarium spp.) is significantly lower where calcium nitrate is the main form of fertilizer. For the most responsive cultivar Hamlin, 15% of trees treated with ammonium nitrate as part of the fertilizer programme were unproductive after ten years, compared to just 7% where calcium nitrate was the only form of N-fertilizer used.

Calcium in fruit - valencia orange, Brazil

Applications of calcium as calcium nitrate to the soil, as well as the crop, reduce the incidence of fruit disorders. This is as a result of increasing calcium levels in the fruit.

Foliar calcium sprays and splitting

Foliar Ca sprays, reduce splitting, creasing (=albedo breakdown) and pitting diseases of oranges and mandarins. For example, Spanish works showed that two calcium nitrate sprays during the summer, reduced splitting of oranges and mandarins.

General guidelines for calcium application

Annual, cumulative use of calcium produces high yield. Calcium nitrate ensures higher yields compared to ammonium nitrate. Fertigation using calcium nitrate is a highly effective way of maximizing Ca nutrition and yield. Significant fruit set improvements come from calcium nitrate applications made immediately prior to and during flowering.