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Fluid Journal : Fluid Journal 2002-2004
1 Fluid Journal Fall 2003 Calcium Nitrate Pays Off on Citrus Industry At Work uring the past 72 years, studies have been conducted in Florida and California to define the value of calcium nitrate fertilizer for cit- rus growth and production. Its ben- efits are threefold: 1) increased tree pro- ductivity and profitability, 2) a healthy root system, and 3) greater tree longev- ity. We'll review these benefits in greater detail. PRODUCTIVITY/PROFITABILITY Hydro Agri research trials (1993 to 1998), conducted in cooperation with the University of Florida, showed citrus fertilized with calcium nitrate yielded 10 to 12 percent more pound solids on young and producing trees, and 7 per- cent more on trees 30 years and older, compared to those fertilized with ammo- nium nitrate. Economically this means production in the range of 3,000 pounds solids per acre (at $0.85 per pound) increased grower gross profit- ability $178 to $306 per acre with just 150 pounds of nitrogen (N) per acre per Reseach indicates increased productivity and profitability, root health, and tree longevity. year. Furthermore, 150 lbs/A of N from calcium nitrate is in compliance with best management practices suggested by the University of Florida's Institute of Food and Agricultural Sciences (IFAS). A 21-year N fertilizer source study in California (1928 to 1949) pro- duced similar results. Trees fertilized with calcium nitrate produced 10 and 23 percent more fruit over the study dura- tion than those fertilized with urea and ammonium sulfate. In a University of Florida study, calcium had a greater im- pact on tree size and production than all other nutrients except potassium (N was supplied to all trees). So, in terms of tree productivity and grower profitability, studies have shown calcium nitrate fertilizer has a definite positive effect and is superior to ammonium nitrate, ammonium sulfate, and urea. ROOTHEALTH Healthy fibrous roots are essential for nutrient uptake by citrus trees. Dimin- ished scaffold and fibrous rooting ca- pacity from soilborne disease reduces tree productivity and profitability. The ammonium form of N (e.g. from ammo- nium nitrate, ammonium sulfate, or urea) has been implicated in the proliferation of fungal root disease organisms such as Phytophthora sp. and Fusarium solani. The nitrate form of N as sup- plied by calcium nitrate, sodium nitrate, and potassium nitrate, appears to re- duce citrus root infection by these pathogens. The fungus Fusarium solani also damages citrus scaffold and fibrous roots. The population of F. solani in- creases significantly following ammo- nium nitrogen application and produces large quantities of naphthazarium phytotoxins that destroy citrus roots. The damaging effects of F. solani can be managed with the application of ni- trate nitrogen. In fact, Fusarium cul- tures in the presence of nitrate from cal- cium nitrate did not produce their root destroying phytotoxins, but thrived and produced large amounts of toxins in the Lane A Lane B Lane C Fusarium naphthazarium toxins extracted from cultures grown with ammonium nitrate (Lanes A and B) and cultures grown with Calcium Nitrate (Lane C) and developed on thin- layer chromatography plates. Note the absence of toxin in the Calcium Nitrate pictured above Fibrous root rot symptoms caused by Fusarium solani in a citrus grove at Bartow, Florida. Figure 1. D
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