Non-irradiated Soil Research Articles

Gaseous Nitrogen Evolution During Nitrification of Ammonia Fertilizer and Nitrite Transformations in Soils

AbstractThe biological oxidation of NO2‐ is inhibited when alkaline‐hydrolyzing N fertilizers are band‐applied to soils, and NO2‐ may accumulate. Nitrogenous gases can be evolved with NO2‐ is added to soil. The aim of the work described here was to determine if gaseous‐N losses could occur via chemical transformations of NO2‐ during nitrification in soils treated with NH3 fertilizer.Evolution of N2, N2O, and NO + NO2 occurred during nitrification in three soils treated with aqueous NH3. Losses occurred when measured soil pH was > 7.5. The highest gaseous‐N loss amounted to 16.5% of applied‐N (1156 µg N applied/g of soil) in a calcareous soil incubated for 28 days at 30°C. Nitrogen was the major gaseous form of N evolved in all soils. In two soils, NO2‐ did not accumulate to more than 13 µg N/g of soil, but substantial N2 emission was measured. Addition of the nitrification inhibitor, nitrapyrin, with the fertilizer, prevented NO2‐ accumulation without preventing nitrification. This treatment prevented N2O evolution and markedly reduced loss of N2 and NO + NO2.Evolution of N2, N2O, and NO + NO2 occurred in the three soils following NO2‐ addition. Loss of N2 was very sensitive to soil pH, and markedly increased with increasing acidity. However, N2 was readily evolved when soil pH was slightly alkaline. Evolution of NO + NO2 was inversely related to pH, but N2O loss was highest in the most alkaline soil (pH 8.4). The marked similarities within individual soils of the patterns of gaseous‐N losses obtained for NH3 and NO2‐ treatments, strongly suggest that similar processes were operating. Gaseous‐N evolution was similar in γ‐irradiated and nonirradiated soils treated with NO2‐. These results, together with the effect of nitrapyrin, suggest that gaseous‐N losses can occur via chemical transformations of NO2‐, when the competitive biological oxidation of NO2‐ by Nitrobacter is inhibited.

Persistence and Degradation of Carbofuran in Soil

The persistence and degradation of 14C-carbofuran and 14C-2,3-dihydro-2,2-dimethyl-7-hydroxy benzofuran were examined in several soils under laboratory conditions. The time required for 50% breakdown of the insecticide varied from 3 weeks to more than 50 weeks. Persistence was influenced by soil sterilization and soil p H. Carbofuran degraded 7–10 times faster in alkaline soil ( p H 7.9) than in acid and neutral soils ( p H 4.3–6.8). 14CO2 was rapidly expired from degraded carbonyl-labeled insecticide in both radiation-sterilized and nonirradiated soils. Degradation of ring-labeled carbofuran was associated with an accumulation of nonextractable radioactivity in the soil residue followed by a gradual evolution of 14CO2. Only minute quantities of carbofuran phenol, the expected hydrolysis product of the insecticide, were recovered from treated soils. Addition of 14C-carbofuran phenol to soil resulted in an accumulation of tightly adsorbed nonextractable radioactivity followed by slow expiration of 14CO2. Indirect evidence suggests carbofuran is hydrolyzed to its phenol which is immediately bound to soil constituents and slowly metabolized by microorganisms.

Duration of viability and the growth and expiration rates of group E streptococci in soil.

In irradiated and nonirradiated feedlot and pasture soils inoculated with group E streptococci, the organism was not recovered 17 days postinoculation from either the irradiated or nonirradiated feedlot soils incubated at 37 C, but survived in the irradiated pasture soils for 24 and 31 days postinoculation. The streptococci survived in irradiated and nonirradiated soils incubated at 4 C for 116 days and in one irradiated feedlot soil for 165 days. The population of streptococci did not increase in either irradiated or nonirradiated soil, and the expiration rate was greater in the soils incubated at 37 and 25 C than at 4 C. With the relatively prolonged duration of viability of group E streptococci in soil at 4 C, it is suggested that soil contaminated with exudate from draining abscesses of infected swine could act as a source of infection during the colder season.

Duration of Viability and the Growth and Expiration Rates of Group E Streptococci in Soil

In irradiated and nonirradiated feedlot and pasture soils inoculated with group E streptococci, the organism was not recovered 17 days postinoculation from either the irradiated or nonirradiated feedlot soils incubated at 37 C, but survived in the irradiated pasture soils for 24 and 31 days postinoculation. The streptococci survived in irradiated and nonirradiated soils incubated at 4 C for 116 days and in one irradiated feedlot soil for 165 days. The population of streptococci did not increase in either irradiated or nonirradiated soil, and the expiration rate was greater in the soils incubated at 37 and 25 C than at 4 C. With the relatively prolonged duration of viability of group E streptococci in soil at 4 C, it is suggested that soil contaminated with exudate from draining abscesses of infected swine could act as a source of infection during the colder season.

Partial purification and properties of a soil enzyme that degrades the insecticide malathion

1. 1. An unusually stable esterase which catalyzes the hydrolysis of malathion to its monoacid was extreacted from irradiation-sterilized soil and non-irradiated soil with 0.2 M NaOH and partially purified by MnCl 2 treatment, (NH 4) 2SO 4 precipitation, dialysis and ion exchange chromatography. A 240-g sample of Chehalis clay loam yielded 28 mg of final preparation. It contained 9.8 mg of protein and hydrolyzed 31 μmoles of malathion in 4 h at pH 7.0 and 37°. Lineweaver-Burk plots obtained for two concentrations of the enzyme gave identical K m values of 2.12·10 −4 M. The enzyme was optimally active around pH 7.0. The enzyme was very stable, being denatured only at temperatures above 70° and by 24-h exposures at pH < 2.0 and pH > 10.0. Lyophilization partially destroyed the activity but no loss of activity occurred during extended storage of enzyme solutions at 4° or frozen at − 10°. 2. 2. When partially purified enzyme was applied to soil, activity was detected for the duration of the experimental period (8 weeks). Its existence as a stable, cell-free soil enzyme is postulated from experimental evidence based on the persistence and adsorptive characteristics of the partially purified enzyme in soil. This esterase should be an excellent tool for investigating enzymatic biological transformations in soil.

The fate of hydroxyatrazine in a soil and a lake sediment

Ring 14C labelled hydroxyatrazine was incubated at room temperature with electron beam irradiated soil under aerobic and anaerobic conditions and in the presence or absence of a non-irradiated soil inoculum. Similar incubation experiments were conducted on a nonirradiated suspension of a lake sediment. A soil incubation at 99°C was also included. Evolution of 14CO 2 indicated that ring cleavage occurred at room temperature for all treatments except that of the uninoculated soil under anaerobic conditions. After 8–12 weeks, the residual hydroxyatrazine and degradation products were extracted with a series of solvents. The extracts were shown chromatographically to contain 14C labelled components other than hydroxyatrazine. No basic compounds were found and it is believed that a portion of the derivatives were compounds which had undergone modification of the ring substituents. Both aerobic and anaerobic species of microorganisms appear to be capable of metabolizing the hydroxyatrazine ring and non-biological chemical processes play no part in these transformations. Circumstantial evidence indicated that little or no chemical incorporation occurred between hydroxyatrazine or its derivatives and indigenous soil organic components.

Gamma Irradiation of Heterodera Schachtii 1)

Recovery of larvae of Heterodera schachtii from soil exposed to 8, 32 and 128 kilorads of gamma radiation exceeded that from non-irradiated soil. Fewer larvae were recovered at 512 k-rads. Damage to H. schachtii at 32 and 128 k-rads was revealed when cyst development and larval emergence were delayed or did not occur in the first and second generation. At intermediate doses of radiation, emergence from young brown cysts was greater than from the control. The converse occurred with white mature females. At the time of irradiation, cysts contained differentiated larvae and females contained embryonating eggs. Emergence from both cysts and females exposed to very high levels of radiation declined.

The availability of organic matter in dried and undried soil, estimated by an anaerobic respiration technique

A study was made of the availability of the organic matter in gamma irradiated and non-irradiated soil, both dried and undried. It was concluded that the release of available soil organic matter during air-drying was the major contributor to the air-drying effect. It was also concluded that the change in microbial populations, which occurred during air-drying, did not contribute significantly to the air-drying effect. In addition it was observed that gamma irradiation affected the availability of soil organic matter in both dried and undried soil, the effect being most marked in the undried soil. It was considered that the anaerobic denitrifying technique which was used in this investigation had definite advantages over aerobic techniques which have been used to study the activity of micro-organisms in soil.