University of California

Chlorate distribution and the effect of nitrate concentration on chlorate toxicity in soil columns


R. S. Rosenfels
A. S. Crafts

Authors Affiliations

R. S. Rosenfels was Assistant Physiologist, Division of Cereal Crops and Diseases, Bureau of Plant Industry, United States Department of Agriculture; A. S. Crafts was Associate Professor of Botany and Associate Botanist in the Experiment Station.

Publication Information

Hilgardia 14(2):71-79. DOI:10.3733/hilg.v14n02p071. October 1941.

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Sodium chlorate is widely used in controlling weeds. The fact that it acts most efficiently as a temporary soil sterilant (3), (5), (6)5 emphasizes the need for accurate knowledge of its behavior in soils.

In an attempt to evaluate the effects of soil type and rainfall on the vertical distribution of sodium chlorate in soils, Crafts (2) in 1935 performed experiments on the slow percolation of sodium chlorate solutions into columns of air-dry soil. Enough solution was allowed to drip upon the soil to just wet the entire column. The column of soil was then separated into ten equal fractions, each of which was mixed and seeded with oats. The plants were grown for 30 days. In view of the fact that in some cases the oats grew normally in soil from the bottom parts of the column, but showed high toxicity in soil from the upper parts of the column, he concluded that the chlorate had been fixed in the upper layers of soil and therefore had not reached the bottom part of the column.

In 1939, experiments reported by Crafts showed that chlorate toxicity in soils is reduced roughly in proportion to the nitrate concentration of the soil solution (4), p. 655-71). This observation suggests an alternative explanation for the low toxicities occurring in some soils near the bottom of a chlorate-treated column.

Literature Cited

[1.] Association of Official Agricultural Chemists. Official and tentative methods of analysis 1935. 4th ed.p.710.

[2.] Crafts A. S. The toxicity of sodium arsenite and sodium chlorate in four California soils. Hilgardia. 1935. 9:461-98. DOI: 10.3733/hilg.v14n02p071 [CrossRef]

[3.] Crafts A. S. Physiological problems connected with the use of sodium chlorate in weed control. Plant Physiol. 1935. 10:699-711. DOI: 10.1104/pp.10.4.699 [CrossRef]

[4.] Crafts A. S. The relation of nutrients to toxicity of arsenic, borax, and chlorate in soils. Jour. Agr. Research. 1939. 58:637-71.

[5.] Loomis W. E., Smith E. V., Bissey Russell, Arnold L. E. The absorption and movement of sodium chlorate when used as an herbicide. Jour. Amer. Soc. Agron. 1933. 25:724-39. DOI: 10.2134/agronj1933.00021962002500110002x [CrossRef]

[6.] Muenscher W. C. Killing perennial weeds with chlorates during winter. New York (Cornell) Agr. Exp. Sta. Bul. 1932. 542:1-8.

[7.] Rosenfels R. S. Determination of chlorate in soil extracts, culture solutions, and plant sap. Jour. Assoc. Off. Agr. Chem. 1938. 21:665-74.

[8.] Shaw C. F. The basis of classification and key to the soils of California. First Internatl. Cong. Soil Sci. Proc. 1927. 4:1-39.

Rosenfels R, Crafts A. 1941. Chlorate distribution and the effect of nitrate concentration on chlorate toxicity in soil columns. Hilgardia 14(2):71-79. DOI:10.3733/hilg.v14n02p071
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