Toxicity of DSMA Soil Residues to Cotton and Rotational Crops

Three facets of the phytotoxicity of disodium methanearsonate (DSMA) incorporated in soils were studied in seven greenhouse experiments. Growth of cotton planted immediately after incorporation of DSMA in Bosket silt loam was reduced significantly by herbicide concentrations of 50 to 80 ppmw. Toxicity appeared to decrease with time, particularly during the first 16 weeks after incorporation. DSMA incorporated in Bosket silt loam at 120 ppmw did not inhibit significantly the growth of cotton planted 32 weeks later. The addition of phosphorus to two silt loam soils increased the toxicity of DSMA to cotton. The incorporation of 50 ppmw of DSMA in Bosket silt loam inhibited rice growth by 75%, soybeans by 39%, oats by 12%, corn and cotton by 10%, and wheat by 0%. Rice growth was not affected in Dubbs silt loam or Sharkey clay by DSMA at concentrations as high as 100 ppmw.