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in the plant anti soil accompany increasing node lation and symbiotic microbial activity. o what is molybdenum? Molybdenum is cne of the seven micronutrients re- quired for the growth and development of plants. Its essentiality for plant life ~Nas discovered about 30 years ago and crop response to molybdenum treat- mentwas first demonstrated commercially in Australia during World War II. Since then, the use of molybde- num in agriculturE~ has spread to many other countries and crops. o what does molybdenum do? Molybdenum is a micronutrient essential to plant growttr. Most plants cannot survive without it because molybdenum is nr;eded to change nitrogen into forms the plant can use. Legumes need more molybdenum than cther crops, such as grass and corn, because the symbiotic ba~;teria living in the root nodules of legum•as require molybdenum to convert elemental nitrogen from the air into a form that can be used by the plant. If insuflicient molybdenum is available, no- dulation will be n~tarded and the amount of nitrogen fixed by the plant will be limited. In general, the amount of molybdenum will determine the amount of nitrogen fixed if other factors are not limiting. As is well known, increasingly vigorous plant growth, high- er protein contents and greater build-up of nitrogen o what kinds of soils may need supplemental molybdenum? Many soils do not have sufficient molybdenum pres- ent in a form plants can use. Soils that may require supplemental molybdenum are: ~F Soils low in organic matter aF Severely er~~ded or heavily weathered soils 9F Soils low in total molybdenum contenT jF Sandy soils ~F Soils high in iron content 9F Acid soils with a pH of 6.3 or less In the United States, this means that molybdenum additions ma~~ be needed east of the Mississif pi and in areas with high rainfall where useful molybdenum may be leached out by rain. Tropical soils also re- quire molybdenum. On the other hand, arid s~~ils, as in the Western United States, may have excessive amounts of soluble molybdenum. o how can you tell if your soil needs molybdenum? Some plants do exhibit specific symptoms, such as the classic whiptail in cauliflower and yellow spot in citrus. In most cases. however, visual charact~~ristics of molybdenum deficiency are not apparent or appear as nitrogen deficiency symptoms. Your agric:ullural extension agent, farm advisor or local agricultural college is the best place to find out if your soil and crops would benefit from molybdenum addit ons. If you do not Have such advisors at hand an~j have