Nitrate production was studied in the field by incubation of the soil in pint polyethylene bags during the 1958-59 winter season. This technique permits the diurnal changes in soil temperature to be taken into consideration in studying microbial processes, such as nitrification.Laboratory studies showed that the rate of nitrification in soil contained in the bags was equal to that contained in ventilated bottles. The bags were tightly closed against the soil and secured with rubber bands. Only slight losses in soil moisture occurred during a 6-week period of incubation. Polyethylene is permeable to oxygen and carbon dioxide. No nitrate difused through the polyethylene bags in a 24-week period.Field studies were made using bags of soil buried at a depth of 4 inches for periods of 1 to 6 weeks. Although soil temperatures at this depth were never below freezing, they varied sufficiently to result in considerable changes in the rate of nitrate production.This technique should also prove to be of considerable value in evaluating nitrification in climates where the soil is frozen or at a temperature near freezing during a portion of the year.

The application of anhydrous ammonia to soil by conventional applicators employing knife‐type injectors results in large concentrations of ammonia in a localized area. The effect of these concentrations on the soil population has been evaluated in several ways. The numbers of fungi and nematodes were reduced by all levels of ammoniacal nitrogen from 136 to 741 ppm. Compared to untreated soil, only 0.6% of the nematodes and 4.9% of the fungi survived when 608 ppm. of nitrogen were present in the soil. This level of ammoniacal nitrogen occurs regularly in the retention zone when anhydrous ammonia is applied in the field. The largest reduction in both nematodes and fungi occurred above 365 ppm. Field studies showed a drastic reduction in all nematodes in the retention zone. Plant parasitic nematodes were greatly decreased and in many cases certain species could not be detected during counting. Reestablishment of the nematodes was greatest among the saprophytic species and was of the same character as that following fumigation with conventional nematocides. The economic value of the reduction of plant parasitic nematodes by anhydrous ammonia, applied primarily for its nitrogen content, will require further work on a field basis. Gross elimination of nematodes is not necessary for successful crop production. Thus, it can be seen that in addition to the primary use of anhydrous ammonia as a fertilizer, the destruction of plant parasitic nematodes in the retention zone also may be of value. Nitrification studies showed this process to be inhibited by concentrations of ammoniacal nitrogen above about 300 ppm. The field situation is probably one where nitrification is inhibited within the retention zone but not at the periphery and, therefore, the nitrifiers gradually reduce the concentration of ammonia centripetally until all of it is utilized.

Red Bay loamy fine sand and Everglades muck were sterilized with gamma radiation, steam, and methyl bromide. Exchangeable NH4+; extractable N, P, and S; moisture equivalent; cation‐exchange capacity; and organic matter were measured. None of the sterilization treatments significantly altered cation‐exchange capacity. Steam significantly increased the amounts of N, P, and S extracted and the organic matter content values, compared to the check and the other two soil treatments; it also significantly decreased the moisture equivalent percentage. Gamma ray and methyl bromide sterilization generally increased the release of N, P, and S above the check. There was also a strong indication, based on the N data, that sterilization by gamma rays disrupted the soil organic materials more than methyl bromide. Finally, the intensity of all these factors is most closely associated with the organic matter content of the soil. Therefore, a sand, for example, would not be altered nearly as much as a loam or an organic soil.

Anhydrous ammonia was applied to several sandy soils which are typical of many soils in Coastal Plain areas. Applications of 58, 115 and 258 pounds per acre of ammonia nitrogen were made at a depth of approximately 5 inches with the injector feet set 13.5 inches apart. Studies were made of the distribution of ammonia around the injection line and of its retention by these soils. The ammonia was found to be concentrated in zones from 2 to 8 inches wide, depending on the soil moisture content. Most of the ammonia was usually concentrated in a zone 3 inches wide at rates of application as high as 258 pounds per acre of nitrogen. This resulted in a very high concentration of ammonia at the injection line. The retention was somewhat variable, but in only one instance, at the 58 pound per acre rate of application, was nitrogen found which equaled that applied. On several soils, losses were shown even at the 58 pound per acre application of nitrogen.

Heptachlor, chlordane, methoxychlor, lindane, aldrin, toxaphene, dieldrin, TDE, DDT, and BHC were applied to Arredondo fine sand at rates of 12.5, 50, and 100 ppm. of the active ingredient. The soil was placed in 2‐gallon pots and maintained in a greenhouse throughout the study. The first crop of Stringless Black Valentine beans, planted 2 weeks after treatment, showed that BHC decreased germination; all other insecticides increased germination or had no effect. Root and top weights were decreased by chlordane, lindane, aldrin, dieldrin, TDE, DDT and BHC. Only top weights were reduced by methoxychlor. Heptachlor and toxaphene had no effect on growth. Germination and root growth of a second crop of beans, seeded 11 months after application of the insecticides, were not affected; top growth was significantly reduced by lindane, aldrin, TDE, DDT, and BHC. Microbial data, obtained 1 month after application of the insecticides, indicated that they had no effect on the numbers of bacteria in the soil. Dieldrin increased the numbers of fungi; all others had no effect. Carbon dioxide evolution was increased by toxaphene, dieldrin, TDE, DDT, and BHC; the others had no effect. Nitrate production was decreased by heptachlor, lindane, and BHC; increased by toxaphene, TDE, and DDT; and unchanged by the others. Sixteen months after application of the insecticides no significant changes occurred in numbers of fungi and bacteria or carbon dioxide evolution. Nitrate production was reduced by DDT and BHC. Based upon the measurements made in this study, the growth of Stringless Black Valentine beans was influenced more than the microorganisms by the presence of insecticides in the soil. Until more specific information on microbial responses to these materials has been obtained, it appears that toxicity of higher plants will be the earliest warning of phytotoxic amounts of chlorinated hydrocarbon insecticides in the soil.