Persistence of 2,4-D Toxicity in Hawaiian Soils

Abstract

The emergence and appearance of aerial organs of successive bean and tomato indicator crops, planted at 2-week intervals, were employed as criteria of persistence or disappearance of 2,4-D in expts. on soils from 5 agric. localities in the Hawaiian Is. The 2,4-D was applied as a surface dust at the rate of 10 lbs. per acre. Depending on soil type, environmental factors, and indicator crop used, 2,4-D toxicity was dissipated from these soils in 2-14 weeks. The bean was more sensitive than the tomato as an indicator crop. The higher the soil temp., the more rapid the rate of dissipation of 2,4-D. Soils high in pH value inactivated 2,4-D more rapidly than those low in pH. Soils in which aerobic bacterial counts were high tended to retain the herbicide in active form for a shorter period than those in which the counts were low. Organic matter content, fertility (application of commercial fertilizer), and adsorptive capacity of the soils were not correlated with the degree of persistence of 2,4-D.