Molybdenum concentration of alfalfa in kern county, California: 1950 versus 1985

Abstract

Greater than 10 mg/kg molybdenum (Mo) concentrations in forage present increasingly challenging management of most classes of livestock. In 1950, 71 alfalfa fields were sampled in Kern County, California, to gain a better understanding of the extent and distribution of high Mo concentrations in forage. Similarly, a large number (82) of the same or nearby fields were resampled in 1985 to evaluate the changes which had occurred in the Mo levels. The number of samples, minimum, maximum and average Mo concentrations were 71, 1.4, 41.7, 10.78 and 82, 0.7, 9.6, 3.57 mg/kg for 1950 and 1985, respectively. Copper (Cu) concentration in 1985 ranged from 6.0 to 19.0 with an average of 10.23 mg/kg. Cu:Mo ratios in 1985 had a low of 1.19 up to 13.71 with an average of 4.25. Forage concentrations of sulfur (S), zinc (Zn), iron (Fe), and selenium (Se) were also determined. Suggested causes for the decline in forage Mo levels are: leaching of soluble salts with irrigation, acidification of soils by nitrogen fertilizers and crop removal. Molybdenosis in livestock is much less of a problem with the decline in molybdenum concentration of forages.

Notes

Department of Land, Air and Water Resources, 129 Hoagland Hall, University of California, Davis, CA 95616.