METHYL-BROMIDE SOIL FUMIGATION ALTERS PLANT-ELEMENT CONCENTRATIONS

Soil fumigation is used to eliminate plant pathogens and weeds in comm ercial practice and to eliminate organisms in controlled experiments, e.g., vesicular arbuscular mycorrhizal fungi (VAMF). This study was co nducted to study the effect of methyl bromide fumigation on plant accu mulation of 14 elements and assess plant colonization by VAMF after fu migation. Field experiments were conducted near Mead, NE, on a Sharpsb urg silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll). C orn (Zea mays L.) sorghum [Sorghum bicolor (L.) Moench], and soybean [ Glycine max (L.) Merr.] were used in the experiments. Fumigation incre ased Al, Br, Ca, Fe, Mg, Mn, and Si and decreased Cu, K, P, and Zn sho ot concentrations in all three plants. Three weeks after germination, shoot Al was sevenfold greater in sorghum and soybean and 16-fold grea ter in corn from fumigated plots than in shoots from nonfumigated plot s. Shoot bromide concentrations from fumigated plots were sixfold grea ter in sorghum and 17- to 18-fold greater in corn and soybean than sho ots from nonfumigated plots. Lower P and Zn shoot concentrations from fumigated plots were attributed to fumigation-induced suppression of V AMF root colonization or an ion balance problem resulting from the enh anced uptake of Al, Br, and other ions after soil fumigation. At harve st, Al was still three- to 10-fold and Br eight- to 20-fold greater in fumigated plot stover compared with nonfumigated plots. This study sh ows that methyl bromide fumigation alteration of plant uptake of Al, B r, Ca, Fe, Mg, Mn, and Si should be considered when interpreting exper iments using methyl bromide soil fumigation.