National Research Centre for Citrus, Amravati Road, Nagpur - 440 010, India.
The history of foliar fertilization in citrus dates back to 1844. Since then it became possible to fulfill the nutritional requirement of citrus through foliar feeding. The efforts are still in vogue to adopt a number of permutation-combinations to improve the efficacy of foliar fertilization. Various plant and environmental factors account for success of foliar fertilization. The most significant breakthrough in the foliar N-fertilization was to postulate the role of elevated level of NH3-NH4 as a result of exogenous application of low - biuret urea and its conversion into various polyamines (Arginine as precursor to spermine). This has provided further insight into the importance of nitrogen metabolism in flowering, since alteration of “on” and “off” year is a common feature especially in mandarins. Foliar application of K preferably as KNO3 has been found highly effective in reducing substantially the problem of creasing and puffing associated with citrus fruits. Foliar fertilization of micronutrients (Fe, Mn, Cu, Zn, B and Mo) using inorganic salts have gained more popularity over their chelated forms probably due to former having greater solubility, easy availability and cheaper cost. Use of suitable surfactant combined with selection of right growth stage with little atmospheric humidity can further ensure the better effectiveness of foliar fertilization using inorganic salts.
