Arsenic Content of Soil and Crops Following Use of Methanearsonate Herbicides

Abstract

Distribution of As with depth in soil was determined after 4 years of repeated applications of monosodium (MSMA), monoammonium (MAMA), and disodium methanearsonate (DSMA) to turf. Arsenic concentrations decreased with depth. Percentage recovery of applied As in the upper 30 cm of soil decreased with increasing application rates. Yields of cotton ( Gossypium hirsutum L.), soybeans ( Glycine max L. Merr.), sorghum‐sudan hybrid ( Sorghum vulgare Pers. × S. sudanense (Piper) Stapf), corn ( Zea mays L.), oats ( Avena sativa L.), vetch ( Vicia villosa Roth), and crimson clover ( Trifolium incarnatum L.) were not affected by previous As treatments. Seed of cotton and soybeans accumulated more As than corn or forage from sorghum or the winter crops. Uptake of residual As was greater from MSMA than from DSMA or MAMA, and from the high rate of application than from the medium or low rates. About 90% of the soil As content occurred in the clay fraction. Much of the soil As was extracted by NH 4 Cl that removed little if any P. Most of the soil P was associated with iron minerals and organic matter, while As was associated with aluminum. No appreciable organic As was found.