Carter (3) in 1943 reported the use of a promising new soil amendment and disinfectant composed of a 50–50 mixture of 1–3 diehloropropene and 1–2 dichloropropane (called “D-D mixture” for short). Among the benefits derived from the use of this mixture in plant tests was the control of the root-knot nematode (Heterodera marioni) in heavily infested soil. Since then other investigators at this institute3have verified the effectiveness of D-D as a nematicide.AnomalaandAdoretuslarvae infesting nursery stock in soil have also been shown to be susceptible to water solutions of D-D mixture (4).Because early observations (3) of pineapple plants grown in the field in soil treated with D-D at 150 pounds per acre gave no evidence of benefit from the treatment until more than a year after application, it was thought that the action of this disinfectant was different from that of others, such as chloropicrin, steam, formaldehyde, and calcium cyanide. The early rapid growth of pineapple plants in soil treated with chloropicrin, resulting in a dark green, broad-leaved, soft, succulent type of plant, was shown to be related to the inhibition of nitrification of applied ammonium, which limited these plants to an ammonium nutrition (12). Since the difference in the time of response of pineapple plants to treatment with D-D and with chloropicrin is important, a comparative study of the nitrogen nutrition of pineapple plants grown in soil following treatment with these two disinfectants was undertaken.