Edaphology of molybdenum nutrition in citrus: A review

Molybdenum is one of the micronutrients, though investigated sparsely, but it hold a good significance in citrus nutrition programme. Yellow spots of citrus, blue chaff of oats and whlptail of cauliflower, broccoli and brussels are some of the classical examples of Mo-deficiency. On the other hand, the reports about Mo-toxicity are very limited but they are known by names like molybdensis, feart disease and peat scows. Some of the Mo-responsive crops besides citrus are: cabbagexs, carrot, cauliflower, celery, cucumber, lettuce, onion, parsnips, potato, radish, spinach, tomato and turnip. The optimum leaf Mo concentration vary from 0.1–3.0 ppm in USA and Brazil to 0.1–1.0 ppm in Australia. While optimum soil available Mo is suggested to be 0.08–0.15 mg/kg, though a very limited literature is available on soil available Mo for citrus. Soil fertilization and foliar application are the two most effective method alleviating Mo-deficiency. The soil application of Mo consists of 500 –1500 g ha⁻¹ and foliar application, 0.05–0.10% with ammonium molybdate still the most popular Mo - source.