THE COMPARATIVE EFFECTS OF A 50–50 MIXTURE OF 1

Publisher Website
Google Scholar
Abstract
A comparative study was made of the effect of D-D mixture (a 50-50 mixture of 1-3 dichloropropene and 1-2 dichloro-propane) and of chloropicrin on the process of biol. nitrification in soil and its subsequent effects on ammonium and nitrate absorption, root development, rate of growth, quality of growth, and total elaboration of organic matter by the pineapple plant. Since plants with the largest root systems made no more growth than plants with the smallest volume of roots on nearly similar nitrate nutrition, it was considered that amt. of top growth and total N absorption were related to the ammonium supply in the soil and, hence, to the suppression of nitrification by the disinfectants. Under the conditions of the present expt., it was found that 200 lbs. D-D suppressed nitrification for 8 wks. and 200 lbs. chloropicrin was inhibitory for at least 24 wks. The application of 400 lbs. D-D was more effective than 200 lbs. D-D, but not so efficient as 200 lbs. of chloropicrin. In every case, leaf nitrate of the pineapple plant correlated with the amt. of nitrate found in the soil. The total amt. of N absorbed by the plants at the completion of a growth period of 35 wks. was lowest in the check treatment, which was on a high-nitrate nutrition. An appreciable increase in absorbed N was found in the 200-lb. D-D treatment, which was on a partial nitrate and ammonium nutrition. The highest amts. of total N were in the plants on a nearly complete ammonium nutrition; namely, 400-lb. D-D, 200-lb. chloropicrin, and 400-lb. chloropicrin treatments. Plants in the check and in the 200-lb. D-D treatment which were supplied with appreciable amts. of nitrate during the growth period were slower-growing, yellower (higher No. 1 yellow-green leaf color and lower conc. of chlorophyll), higher in % dry matter, lower in total dry matter, and absorbed smaller amts. of available soil N than plants in the other treatments. The plants growing in soil treated with 400 lbs. D-D, 200 lbs. chloro-picrin, and 400 lbs. chloropicrin were restricted to am-monium as a source of N and were characterized as a high-nitrogen, dark green (low No. 1 yellow-green and high chlorophyll content), fast-growing (high total dry mat-ter), broad-leaved, soft, and succulent (low % dry matter) type. Although no nematode galls were formed on the root systems of the plants in any of the treatments, ex-aminations for non-gall-forming nematodes indicated D-D to be a more efficient nematicide than chloropicrin. Delayed response of pineapple plants to D-D may be related . to improved root systems at maturity due to control of root pathogens by the disinfectant. The use of sufficiently high concs. of D-D to inhibit nitrification in soil will be evidenced by early response resulting in the typical ammonium plants seen after chloropicrin treatment of soil.