Germination of Seeds in Soil Containing 2,4-Dichlorophenoxyacetic Acid

Abstract

2,4-Dichlorophenoxyacetic acid (2,4-D) was mixed in various amts. with batches of soil which were then stored, some air dry and others moist, for various periods of time. Seeds of mustard, barley and annual morning glory were planted in aliquots of the various mixtures at intervals during the storage periods and the effect of the acid-soil mixtures on the emergence of the seedlings observed. 0.1 mg. of 2,4-D per lb. of soil significantly reduced the % of emergence of mustard planted in an acid-soil mixture that had been stored air dry for 1 month, and concs. of 1 to 14 mgs. reduced its emergence by 80-90% below that of plants in untreated soil. Although tests with mustard showed that 2,4-D was slowly inactivated when mixed with air dry soil, it still reduced the emergence of mustard plants by a significant amt. after a storage period of 18 months in mixtures that contained 1 or more mgs. per lb. of soil. The rate of emergence of barley plants was retarded by all concs. of 2,4-D (0.1 to 14 mgs. of acid per lb.) in tests made after the 2,4-D-soil mixtures had been stored in an air dry condition for 12 days. After 1 month storage, rate of emergence of barley plants was retarded in a soil mixture having 14 mgs. of acid per lb., while the lower concs. of the acid stored 1 month in dry soil did not significantly affect the rate of emergence or the final number of plants that emerged. After 6 months storage, the rate of emergence of barley plants was not adversely affected by any of the 2,4-D-soil mixtures studied. After 1 month''s storage in an air dry condition, soil containing 4 mgs. 2,4-D per lb. reduced the emergence of mustard plants by approx. 90%, while the emergence of barley seedlings in another sample from the same batch of soil was unaffected. 2,4-D was readily inactivated when mixed with warm moist soil. 20 mgs. of 2,4-D per lb. of soil did not significantly reduce the emergence of mustard plants in soil relatively high in organic matter, which had been kept warm and most during storage for a period of 2 weeks or longer.