The effect of a,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) on the growth of cotton seedlings was studied under greenhouse conditions as influenced by dosage, 0.25, 0.5, 0.75, and 1.0 lb/A, and depth of soil-incorporation, 0 to 6 in in 0.5-in increments; the cotton seed were planted 1.5 in deep and watering was by subirrigation.
Trifluralin caused stunting in height of cotton seedlings and prevention of lateral root growth. The dosage of the chemical influenced the degree and persistence of stunting more than did depth of incorporation. Marked stunting occurred at 1 lb/A at all depths of incorporation and persisted for the duration of the experiments, about 1 month; slight to moderate stunting occurred at 0.75 lb/A or less but was of short duration, 1 to 2 weeks. Lateral root growth was affected more by depth of incorporation than by dosage; though the growth of the taproot was essentially unaffected, the growth of lateral roots was completely prevented by even the lowest dosage applied, 0.25 lb/A, incorporated to the greatest depth, 6 in. Root growth was prevented only along that portion of the taproot growing in treated soil; when trifluralin was incorporated above the seed, root development was unaffected. Stunting occurred independently of the effect on root growth.