Molybdenum in Everglades Soils and Plants

Everglades organic soils are underlain with limestone rock, and with continued cropping subsidence occurs and pH values rise. A rather high total Mo content in these soils encouraged work to determine the Mo accumulation by plants as affected by soil factors. A survey of Mo and Cu contents of forages grown throughout the area also was made to determine the Mo status of forages being grazed. As an index of forage not harmful to grazing cows, a Cu content of 10 ppm., or greater and a Mo content of 3 ppm. or less in the forage was chosen from previous animal tests. It was found that increasing the pH of the soil resulted in Mo accumulations of greater than 25 ppm. by clover plants. Not only is there a great difference between Mo contents of various winter forages grown under the same conditions, but contents seem to vary as a result of plant maturity and season. Roselawn St. Augustinegrass and Bermudagrass growing in commercial pastures were found to absorb less Mo than other grasses tested, while pangolagrass and white clover absorbed larger amounts. Furthermore, trends seem to indicate that plants grown on a given soil will accumulate more Mo as the period of cropping increases, even though the soil pH remains constant. Although the Mo contents of permanent pastures are not as high as those reported in other troubled areas, the Mo‐Cu status indicates the possibility of unfavorable forage quality during the fall. Average Mo and Cu contents of approximately 100 survey samples were found to be 5.5 and 7.4 ppm., respectively, in the fall, and 2.9 and 10.9 ppm. in the spring.