Earlier the original source of phosphorus (P) fertilizer was bones; as time passes, the supply of P fertilizer will get exhausted. Today, rock phosphate is the only raw material in the form of P fertilizers. There are two types of rock phosphates: igneous and sedimentary; both have the same phosphate mineral, i.e., calcium phosphate of apatite group. The general formula for pure rock phosphate is Ca 10 (PO 4 ) 6 (X) 2 , where X is F − , OH − or Cl − . These minerals are called apatites. The most common rock phosphate mined is fluorapatite, which contains impurities like CO 3 , Na and Mg. Carbonatefluorapatite (francolite) is primary apatite mineral in the majority of phosphate rocks.The high reactivity of some phosphate rocks is due to the occurrence of francolite. The major deposits are found in the US followed by China, Morocco and Russia. The US produced about 33% of the world's rock phosphate, although nearly 50% of the world reserves are in Morocco. P fertilizers are produced from either acid-treated or heat-treated rock phosphate to break the apatite bond and to increase the water soluble P content. There are many commercially available P fertilizers like rock phosphate, phosphoric acid, calcium orthophosphates, ammonium phosphates, ammonium polyphosphate and nitric phosphates.

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The present study was done on the hypothesis that excess sodium chloride (NaCl) in the soil decreases the growth and yield of Cichorium intybus L. To investigate this hypothesis, a pot experiment was conducted in which chicory seeds were sown in garden soil-filled earthen pots and treated with three different doses of sodium chloride (45, 75, and 105 mM kg-1 soil) except the control, and each treatment was replicated three times. The results revealed that all the saline treatments significantly (p≤0.05) reduced the vegetative (including root and shoot length, dry weight, number of leaves, leaf area, number of branches, and photosynthetic pigments) and reproductive (mean fruit number/plant, mean seed number/fruit, and total seed yield/plant) growth parameters of Cichorium intybus. On increasing NaCl concentration in the soil, chlorophyll content significantly (p≤0.05) decreased while proline content in the fresh leaves increased significantly (p≤0.05). From the results, it is concluded that Cichorium intybus L. can tolerate a moderate level of sodium chloride stress (45-75 mM NaCl kg-1 soil) but is sensitive to high doses of sodium chloride stress (105 mM NaCl kg-1 soil).

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