Molybdenum Deficiency in Serpentine Barren Soils

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Abstract
Tomato plants were grown in pot culture expts. to test the effect of variations in the soil Ca level. Marked responses to increased Ca were obtained, with abnormalities identical with those characterizing Mo-deficient plants. The Mo content of these plants was detd. and found to be less than 0.1 ppm. on a dry wt. basis. The affected plants recovered after supplying them with Mo. Three methods were used: application of small amts. of Mo salts to the soils; painting of leaflets with a dilute soln. of Na2Mo04; and direct infiltration of Na2Mo04 into cut leaflet tips. The specific procedures are descr. in detail. The same symptoms were seen in tomato and corrected through Mo fertilization on 2 other serpentine soils. Evidence also indicates that Romaine lettuce suffers from Mo deficiency on the one soil tested; supplying Mo relieves the symptoms. The 3 soils involved are shallow, primary hillside soils overlying crystalline serpentine rock in Lake and Marin Counties, California. The areas are sharply delimited serpentine barrens with characteristically sparse endemic floras. Presence of Mo deficiency in these soils from different areas and varying widely in organic matter content, suggests that low available Mo may be a general chem. characteristic of primary soils weathered on serpentine parent material.