Nitralin


Nitralin is a selective preëmergent dinitroaniline herbicide that is closely related to trifluralin, and released two years later in 1966. Today it is largely obsolete. It was used in the USA, France and Australia to control annual grasses and broad-leaved weeds, and was applied on vines, crops and turf.
American farmers used in 1974, though trifluralin still overshadowed it, with. A 1992 report mentions extensive use on potatoes, though Shell's "Planavin" trademark expired in 1989.
On ryegrass meristems, nitralin suppressed elongation and made the roots wider. After 1 hour, mitosis was reduced by 76%. Cell nuclei expanded, becoming polymorphic, and with increased ploidy levels. Other dinitroanilines have similar effects, except butralin.
Nitralin is not associated with lung cancer.

Planavin

Planavin 75 was sold commercially as a wettable powder containing 75% nitralin, applied at around 2 pounds per acre, equivalent to 1.5 lbs/acre of pure nitralin. Shell sold technical grade nitralin at 94% purity for manufacturing purposes.

Environmental Behaviour

Soil-applied nitralin is involatile; its vapours were below the limit of detection. Water leaching is very slow. Together this makes nitralin immobile in soil, so application can be precise, though it cannot move far enough into soil to control deep-germinating weed species. Typical in-soil halflives are 30 to 60 days, and it decomposes under ultraviolet light.

Metabolism

Ingested by rats, 98.5% is removed in 72 hours by urine and faeces. The metabolism is complex and produces many afterproducts.

Comparative Performance

Compared to trifluralin, nitralin is more toxic to the roots and less toxic to the shoots. Trifluralin prevented emergence of most species tested; nitralin did not prevent any from emerging. At Johnsongrass control, nitralin and pendimethalin lost out to trifluralin and other dinitroaniline herbicides.
Nitralin in a 1970s trial on conifer seedbeds in Connecticut was effective at 2 lbs/ac though it damaged white spruce seedlings in one test. Of the related dinitroanilines, oryzalin was most active, and nitralin was not far off, beating trifluralin.

Applications