University of California

Toxicity of arsenic, borax, chlorate, and their combinations in three California soils


A. S. Crafts
C. W. Cleary

Authors Affiliations

A. S. Crafts was Assistant Professor of Botany and Assistant Botanist in the Experiment Station; C. W. Cleary was Formerly Technical Assistant in the Botany Division.

Publication Information

Hilgardia 10(10):399-413. DOI:10.3733/hilg.v10n10p399. December 1936.

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In weed control it is often desirable to apply two or more chemicals at the same time. Where, for example, both annuals and deep-rooted perennials occur, arsenic and chlorate combined may be used for complete sterilization. In such cases one must know the reciprocal effects of these reagents in order to use them with any assurance of success. This paper describes experiments designed to show the toxicity of three common herbicides used two and three at a time in three California soils.

Toxicity Studies

Tests on the toxicity of sodium arsenite and sodium chlorate (2)4 and sodium borate (3) used separately, in these soils have been published and the technique has been described. Briefly, it consists in growing indicator plants, Kanota oats in this case, in soil cultures in No. 2 cans. The chemicals being studied are added to the air-dry soil, dissolved in sufficient water to bring the soil to its field capacity. The cultures are then seeded and grown for 30 days, at which time the height and fresh weight of the indicator plants are recorded.

In the preliminary toxicity tests (2), (3) concentration series were used covering the complete range from 0 to 100 per cent toxic and beyond, so that cultures were included that showed no plant growth even after several croppings. In the present experiments two arbitrary growth levels were selected: the 50 per cent level at which growth was reduced to approximately one-half that of the untreated checks, and the 10 per cent level at which growth was correspondingly reduced to a low value. The concentrations used to produce growth at these two levels were derived from the original toxicity curves, the data from the first runs with the three chemicals being computed in terms of percentage of checks. Table 1 gives the values expressed as parts per million in terms of the air-dry soil. For the borax they have been converted to the hydrous form that contains 47 per cent water by weight.

Literature Cited

[1] Crafts A. S. Plot tests with sodium arsenite and sodium chlorate as soil sterilants in California. California State Dept. Agr. Mo. Bul. 1935. 24(4, 5, 6):247-59.

[2] Crafts A. S. The toxicity of sodium arsenite and sodium chlorate in four California soils. Hilgardia. 1935. 9(9):459-98. DOI: 10.3733/hilg.v09n09p459 [CrossRef]

[3] Crafts A. S., Raynor R. N. The herbicidal properties of boron compounds. Hilgardia. 1936. 10(10):343-74. DOI: 10.3733/hilg.v10n10p343 [CrossRef]

Crafts A, Cleary C. 1936. Toxicity of arsenic, borax, chlorate, and their combinations in three California soils. Hilgardia 10(10):399-413. DOI:10.3733/hilg.v10n10p399
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