Ammonia Nitrogen Production Research Articles

Effect of settled sludge on dissolved ammonia concentration in tanks used to grow abalone (Haliotis midaeL.) fed a formulated diet

The relative contribution that solid waste or ‘sludge’, which accumulates at the bottom of abalone (Haliotis midae L.) tanks, makes to dissolved ammonia has not been established. Sludge was allowed to accumulate in 10 fully stocked abalone tanks, fed a formulated feed (Abfeed®; Marifeed, South Africa), for 24 days. Sludge was subsequently siphoned from five of these tanks. Total ammonia nitrogen (TAN) production and toxic, free ammonia nitrogen (FAN) were recorded in the tanks from which sludge was removed and compared with those from which sludge was not removed over the subsequent 50 h. Tanks with neither abalone nor sludge present were used as a control. The mean production of TAN (±standard deviation) was an average of 44% higher in tanks from which sludge was not removed compared with those from which it was, indicating that the sludge was a significant contributor to dissolved ammonia in the tanks. The toxic FAN concentrations were correspondingly higher in tanks with sludge present (2.3±0.3 μL−1) compared with cleaned tanks (1.9±0.1 μL−1). Our results indicate that regular removal of sludge from abalone tanks should significantly reduce the dissolved ammonia levels, thereby improving water quality in the culture environment.

Effect of salinity level in drinking water on feed intake, nutrient utilization, water intake and turnover and rumen function in sheep and goats.

Twelve adult males of each Baladi goats and Barki sheep were divided, each, into four groups based on body weight. Animals were fed a ration consisted of berseem hay (ad lib) and concentrate feed mixture (at the rate of 1.5% of body weight). Treatments were drinking sea water diluted with fresh water to contain 4.04g, 8.15g, and 12.33g total dissolved salts/100 ml (TDS l-1), for 2nd, 3rd and 4th treatments, respectively along with fresh water (0.42 g TDS l-1) as a control. Feed intake of both sheep and goats increased by increasing level of salinity, while species differences existed (P<0.05). Nutrient digestibility coefficients did not differ significantly due to salinity levels. Salinity levels effect appeared significant (P<0.05) on nitrogen utilization. Water intake increased in response to increasing salinity level till 8.15g TDS l-1, and then decreased at the higher level (12.33 g TDS l-1). Water intake response to load of elevated salt was higher in sheep than goats. Neither ammonia nitrogen nor total volatile fatty acid production were affected by salinity level while species effect was found to be significant (P<0.05 for NH3-N and P<0.0001 for TVFA's). Quadratic regression analysis revealed variations over time of both metabolites due to increasing salinity levels. The ruminal pH values were significantly affected by increasing salinity in drinking water. Both salinity levels (8.15 and 12.33g TDS l-1) showed lower ruminal pH than that of fresh water (0.42g TDS l-1). Drinking fresh water resulted in ruminal pH similar to that of the lowest salinity level (4.04g TDS l-1). Sheep had higher (P<0.0001) ruminal pH value (7.309) than goats (7.156). Turnover rate of fresh water was significantly (P<0.05) lower than water of higher salinity levels. The increments in turnover rate as a result of increasing salt concentrations were 42, 84 and 111% for 4.04, 8.15 and 12.33g TDS l-1, respectively. Sheep turned over more water (12%) than did goats. Relative stabilization of the rumen fermentation appeared to be restored at about the 21st day from the beginning of the treatments.

The effect of feeding varying levels of Leucaena leucocephala on intake and digestibility of low-quality forages in the Highveld of South Africa

The purpose of this study was to determine the effect of varying levels of Leucaena supplement on the intake, flow and digestibility of nutrients of two low-quality forages. Partial digestion methods were used. The overall results showed that the supplementation of veld grass with Leucaena hay improved the performance of veld grass more significantly (P < 0.05) than the supplementation of Eragrostis grass with Leucaena hay. The crude protein of Diets 2–4, which contained veld grass, increased by 67.1%, 95.3% and 130.6%, compared with the control diet, while the in vitro organic matter digestibility increased by 15.5%, 25.7% and 15.24%, respectively. Similarly, neutral detergent fibre content decreased by 6.5%, 14.7% and 23.3%, respectively. Feed intake increased by 22.7%, 14.9% and 11.3%, and crude protein intake increased by 2.13, 2.25 and 2.57 times, respectively. The production of ammonia nitrogen increased by 17%, 38.4% and 44.3%, and volatile fatty acids increased by 31.3%, 28% and 26%, respectively. The flow of non-ammonia nitrogen through the abomasum increased by 3.28, 3.9 and 4.76 times, respectively. The disappearance of organic matter from the rumen increased by 29.3%, 36.2% and 24.7% and in the small intestine increased by 1.8, 2.3 and 2.2 times, respectively. The overall digestibility of organic matter in the whole digestive tract was increased by 9.9%, 16.3% and 9.7%, respectively. In comparison, the crude protein of Diets 6–8, which contained Eragrostis grass, increased by 37.5%, 80% and 103.3%, compared with the control, while the neutral detergent fibre content decreased by 4.8%, 14.8% and 21.6%, respectively. Feed intake increased by 41.3%, 36% and 28.4%, and crude protein intake by 1.93, 2.43 and 2.52 times, respectively. The production of ammonia nitrogen increased by 13.8%, 25% and 21.7%, and volatile fatty acids increased by 18.8%, 17.4% and 14.7%, respectively. The flow of non-ammonia nitrogen through the abomasum increased by 1.27, 166 and 1.50 times, respectively. However, there was no significant effect on the flow of the other nutrients. However, the overall digestibility of organic matter was not significantly different from that of the control diet. The conclusion was that the supplementation of the poorer forage with Leucaena was more beneficial and more cost-effective than the supplementation of the better-quality forage with Leucaena.

Fermentative Quality of Guineagrass Silage by Using Fermented Juice of the Epiphytic Lactic Acid Bacteria (FJLB) as a Silage Additive

This experiment examined the characteristics of fermented juice of epiphytic lactic acid bacteria (FJLB) prepared by the addition of glucose, sucrose and molasses as a fermentation substrate. The effect of FJLB on the fermentative quality and changes in chemical composition during fermentation of guineagrass silage were also investigated. The pH value of the silages treated with FJLB rapidly decreased, and reached to the lowest value within 7 days of start of fermentation, as compared to the control. The number of lactic acid bacteria (LAB) in the treated silages increased for the first 3 days, thereafter the number of LAB declined gradually up to the end of the experiment. Silages treated with FJLB had larger populations of LAB than the control. Ammonia-nitrogen production increased throughout the ensiling period, which in the control and no-sugar added FJLB silages were higher than the other treated silages. Lactic acid levels varied with the time of ensiling and among the silage treatments. For any sugar FJLB treated silages, the lactic acid increased initially, and then slightly reduced to less than 50 g/kg of dry matter until 49 days after ensiling, except the silage treated with glucose added FJLB. Nevertheless, lactic acid content of the control decreased constantly from the beginning of ensiling and was not found after 35 days. Moreover, acetic acid content increased throughout the ensiling period. All the FJLB treated silages had significantly (p<0.05) lower pH and ammonia-nitrogen content, while significantly (p<0.05) higher lactic acid content and V-score value compared with the control. This study confirmed that the applying of FJLB with any sugar substrate improved fermentative quality of silage. (Asian-Aust. J. Anim. Sci. 2005. Vol 18, No. 6 : 807-811)

Effect of temperature and pH on the kinetics of methane production, organic nitrogen and phosphorus removal in the batch anaerobic digestion process of cattle manure

A study of the effect of temperature and pH on the kinetics of methane production and organic nitrogen and phosphorus degradation in the anaerobic digestion process of cattle manure was carried out. Two laboratory-scale batch completely mixed reactors, operating at 35 °C (mesophilic temperature), and other two, operating at 60 °C (thermophilic temperature) were used. For each temperature selected, the influent pH values were 7.6 (initial pH of the waste used) and 7.0. The apparent kinetic constants of the biomethanization process increased 2.3 times when the initial pH of the influent was increased from 7.0 to 7.6 at mesophilic temperature. The values found at thermophilic temperature were similar. The kinetic constants of methane production decreased 2.6 and 7.2 times when the operating temperature increased from 35 °C to 60 °C for the experiments carried out at initial pH of 7.0 and 7.6, respectively. The methane yield coefficient (l CH4 STP/g VS removed) also decreased when the temperature increased from 35 °C to 60 °C for the two initial pH values studied. This behaviour agreed with the major inhibition level observed at thermophilic temperature as a result of the higher organic nitrogen removal and ammonia nitrogen production observed at 60 °C. Specifically, the specific rate constants for organic nitrogen removal and ammonia nitrogen production increased 3.6 and 12 times when the temperature was increased from 35 °C to 60 °C for the experiments carried out at initial pH values of 7.0 and 7.6, respectively. In the same way, the values of the kinetic constant for phosphorus removal were 44% and 80% higher than those obtained at 35 °C for the two initial pH values above-mentioned, respectively. Finally, the experimental values of organic nitrogen and phosphorus concentrations were reproduced with deviations equal to or less than 10% and 15% in every case, respectively.

Apparent ammonia-nitrogen production rates of white sturgeon ( acipenser transmontanus) in commercial aquaculture systems

Ammonia production rates of white sturgeon ( Acipenser transmontanus) were measured at three commercial farms in the Sacramento, California area. Mean daily ammonia-nitrogen production (RNH3) values ranged from 1.5 to 27.6 mg total ammonia-nitrogen (TAN) (kg fish) −1 h −1 for sturgeon ranging in size from 0.09 to 3.8 kg. Peak hourly average ammonia production rates were observed to occur 2–6 h after the consumption of a meal, reaching values as high as 1.4 times the mean daily values. Multiple regression analysis determined that 87% of the variations in the RNH3 values could be attributed to variations in protein ration, and the protein ration was the only variable considered which was significant in predicting the mean daily ammonia production rates.

Microbial amino acid yield from in vitro incubation of cellulose or starch with rumen fluid

Two model substrates, cellulose (particle size 20 μm) and powdered maize starch, were incubated in vitro in glass syringes with rumen fluid and buffer. The fermentation was monitored after 1 h and every 3 h, up to 24 h of incubation. At the end of each incubation period, gas yield was read and the contents of three syringes were removed, separated and analysed. Bacterial dry matter was calculated from total amino acid yield, assuming that this represented 42% of bacterial cells, and substrate degradability was calculated as the difference between residual dry matter and estimated bacterial dry matter at the end of each incubation period. The results obtained for pH, ammonia nitrogen and gas production indicated that the fermentation of cellulose was active from 9 to 21 h of incubation. For starch, the active period of fermentation was considered to occur between 3 and 15 h. The amino acid production was significantly different between substrate and times of incubation ( P < 0.001); moreover the interaction of the main effects was also very high ( P < 0.001). At the end of the selected incubation periods times (21 h for cellulose and 15 h for starch) the quantity of amino acid yielded from the bacteria growing in cellulose was much lower than that obtained from starch (59.4 vs. 89.8 mg AA g −1 substrate incubated). The amount of lysine and methionine produced during the fermentation of cellulose and starch varied between substrate and time of incubation. The in vitro estimated degradability differed significantly for substrate, time of incubation and their interaction; at the end of the restricted period of incubation considered, the degradability reached a value of 52.7 and 91.8% for cellulose and starch, respectively. The efficiency of bacterial growth (mg AA nitrogen g −1 substrate degraded) was numerically, but not significantly higher for cellulose than starch (19.3 vs. 15.8 mg AA nitrogen g −1 respectively) and at the beginning of incubation for both the substrates.

The influence of feed protein intake on tilapia ammonia production

Biological filters designed to remove toxic ammonia excreted as fish wastes are an integral part of any recirculating aquacultural system. The quantity of ammonia excreted by fish is related to the quantity of nitrogen supplied by the protein contained in feed. This experiment evaluated short term Total Ammonia Nitrogen (TAN) production by juvenile tilapia fed rations with six different protein contents. Five feeds composed using soybean meal as their protein source and one feed deriving most of its protein content from fish meal were tested. Statistically significant increases ( P < 0·10) in TAN production were observed as protein content increased during the 24 h period following feeding. Fish meal and soybean meal did not produce statistically different TAN production rates.

Diel Dissolved Oxygen Consumption and Total Ammonia Nitrogen Production by Fingerling Channel Catfish following Feeding at Different Times

Abstract Diel total ammonia nitrogen (TAN) production and dissolved oxygen (DO) consumption rates were characterized for fingerling channel catfish (Ictalurus punctatus) following a feeding at 0800 or 1600 hours. Mean hourly TAN production rates of channel catfish fed at 0800 hours ranged from 10.1 to 64.4 mg N/kg; rates for fingerlings fed at 1600 hours ranged from 8.9 to 105.4 mg N/kg. Hourly oxygen consumption averaged from 148.7 to 326 mg/kg for channel catfish fed at 0800 hours and from 295.8 to 462.0 mg/kg for fish fed at 1600 hours.

Lactic acid fermentation in silage preserved with formic acid

A study has been made of silages preserved with formic acid (4.6 g kg −1), in which the content of residual sugar in the aqueous phase was at least 10 g l −1, thus permitting lactic acid fermentation. The mean (± SD) pH of the direct-cut silages was 3.87 ± 0.21. The factors studied accounted for most of the variation in silage acidity. In lactic acid fermentation in silage, 0.20 g acetic acid, 0.031 g ammonia-nitrogen and 0.090 g soluble nitrogen are produced with each gram of lactic acid, and 1.8 g reducing sugars are consumed. The other silage microorganisms, referred to here as spoilage microorganisms, also produce acetic acid, ammonia-nitrogen and soluble nitrogen. The production of acetic acid by the spoilage microorganisms is largely independent of the degradation of protein. For every gram of acetic acid produced by spoilage microorganisms, 3.6 g of sugar are consumed; the production of ammonia-nitrogen and soluble nitrogen does not result in a loss of sugar. For the ionisation of the amino acids released in protein degradation, 2.3 g of lactic acid are required for each gram of amino acid nitrogen. A surprising result was that the production of acetic acid increases that of lactic acid by 0.55 g for each gram of acetic acid, whereas the production of ammonia does not increase the content of lactic acid in well preserved silage. This study is based on the analysis of 61 036 silage samples which the farmers have sent to the silage laboratories.

Drying Temperature and Time Affect Quality of Chinese‐style Sausage Inoculated with Lactic Acid Bacteria

ABSTRACT Lactobacillus plantarum, Streptococcus thermophilus and a commercial culture (DS‐66) were used as starter culture for manufacturing Chinese‐style sausage. The influence of drying temperature and time on the growth of lactic acid bacteria (LAB) and on changes in quality were determined. After drying the sausage at 370 and 45°C for 12 hr, the population of LAB had increased from an initial 106 CFU/g to 108 and 107 CFU/g, respectively. The pH value was the lowest for the sausage dried at 37°C. Nitrite residuals decreased rapidly with increased drying time. Starter cultures increased the amino nitrogen level and suppressed ammonia nitrogen production.

Glucose Oxidase/Catalase Solution for On‐board Control of Shrimp Microbial Spoilage: Model Studies

ABSTRACTThe potential of an immersion system of glucose oxidase (GOX, 1 unit/ml) and catalase (CAT) added to 4% w/v glucose in artificial seawater was determined for on‐board shrimp preservation. Fresh shrimp were frozen, radiation‐sterilized, thawed by adding artificial seawater and inoculated with Pseudomonas fluorescens (lo4 CFU/g shrimp). Samples were stored at 1°C and treated after 24 hr or left as controls. Changes in shrimp and solution were monitored by total plate counts, ammonia and total volatile nitrogen. Solution discoloration due to shrimp melanosis was followed spectrophotometrically. Microbial lag phase was extended 44 5 d and after 14 d, GOX/CAT had reduced browing by ∼80% and inhibited ammonia and total volatile nitrogen production. Due to increase in nitrogen compounds, the enzyme solution should be replaced after 14 days.

Ensiling characteristics of cattle waste fermented with wheat straw and green berseem ( Trifolium alexandrinum)

Cattle waste was fermented using 4 different treatments. The ingredients of the premix were wheat straw, cattle dung, berseem and sugarcane molasses in the ratios 20:0:75:5, 20:25:50:5, 20:50:25:5 and 20:75:0:5, respectively, in Treatments 1–4. The dry matter in the premix varied between 32 and 34%. The biochemical characteristics of silage were studied after 7 and 28 days of fermentation. With an increasing level of waste in the premix, there was a decrease in the soluble sugar content, lactic acid volatile fatty acid production. There was also a decrease in the production of ammonia nitrogen and soluble nitrogen during the process of ensiling with every unit increase of cattle waste in the premix. However, the ratio of lactic acid to volatile fatty acids increased and the ammonia nitrogen as a percentage of total nitrogen decreased with the inclusion of cattle waste in the wastelage premix. Cattle waste can be included in berseem silage at a level of 13–26% of the total dry matter without adversely affecting the silage characteristics.

Evaluation of cardboard and dried poultry waste as feed ingredients for ruminants

The nutritive values of cardboard and cage hen manure (CHM) for ruminants were evaluated using chemical analyses, alkali treatment, ensiling, in vitro digestion studies and in vivo digestion studies. Cardboards treated with or without alkali (4% NaOH or NH 4OH) were analyzed for chemical components. Other samples were supplemented with various N supplements (cottonseed meal (CSM), feather meal, urea and CHM plus urea) and used as substrates for in vitro fermentation. Ammonia nitrogen (NH 4-N) and volatile fatty acid (VFA) production were also determined. Cardboard silages (ensiled in polyethylene bags) consisted of untreated and NaOH-treated cardboards with or without cane molasses (10%) supplemented with various levels (10–50%) of CHM. Silage samples were evaluated for pH, dry matter loss and crude protein (CP) loss and also used as substrates for in vitro incubation and NH 4-N production. In vitro digestibility by sheep (20 wether lambs) of diets containing various levels of ground cardboard with and without poultry manure was determined by the total collection method. A control diet made up of ground corn, chopped ryegrass straw, cane molasses and CSM was compared with diets in which 15 or 30% cardboard replaced the same amounts of straw and a fourth diet (30% cardboard) in which CHM replaced 25% of the N supplied by the CSM. NaOH treatment decreased the fiber content, increased the ash content and increased in vitro fermentation of cardboard, while NH 4OH treatment increased CP content. Increased total VFA resulted from both NaOH and NH 4OH treatment. Supplementation with urea or CHM plus urea increased total VFA and propionic acid production. NaOH treatment enhanced microbial fermentation on cardboard silages, especially when supplemented with molasses. Silages did not undergo as much fermentation as expected. Cardboard silage was readily fermented by rumen microorganisms, especially when treated with NaOH and supplemented with molasses and CHM. In vivo digestibilities of dry matter, organic matter and gross energy were highest ( P < 0.05) for the 30% cardboard diet followed by the CHM diet. CSM was a better ( P < 0.05) source of digestible crude protein than CHM. Cardboard fiber was more readily digested ( P < 0.001) than that of ryegrass straw and the addition of CHM improved digestibility of cardboard fiber. Digestibility of the inorganic components of the diets (Ash) decreased ( P < 0.001) with each addition of cardboard and was further decreased with the addition of CHM. Fecal N increased slightly ( P < 0.05) when cardboard was fed and again when CHM was fed. N retention was increased ( P < 0.05) by each addition of cardboard, but decreased (to the 15% cardboard level) when CHM was added to the diet. The results indicate that (a) cardboard and CHM can be utilized effectively by rumen microorganisms; (b) alkali treatment (especially with NaOH) and ensiling of cardboard-CHM diet will improve its utilization; (c) cardboard and CHM can be fed to growing lambs to obtain a moderate to good level of production.

A Model of Fish Growth in Aquaculture

A model of fish growth is formalized. The parameters are determined by aquaria experiments with rainbow trout (Salmo gairdneri). From the model the following terms can be found independently: Ingested food, growth, production of ammonia-nitrogen, settable and non-settable faeces, and oxygen consumption. Ingested food is determined as a function of temperature and fish size. The other terms are determined as functions of ingested food, temperature and fish size. The terms are balanced in energy or nitrogen. The model can e.g. be used in connection with production planning in fish farms and as a submodel in aquatic ecosystems

Metabolism of Cysteine and Cysteinesulfinate in Rat and Cat Hepatocytes

The metabolism of cysteine and cysteinesulfinate was studied in freshly isolated hepatocytes from fed rats and cats. In incubations of rat hepatocytes with cysteinesulfinate, the rate of hypotaurine plus taurine production was approximately the same as the rate of conversion of the 1-carbon of cysteinesulfinate to CO2. In contrast, no significant production of hypotaurine plus taurine occurred in incubations of cat hepatocytes with cysteinesulfinate. These data are consistent with the species difference in the activity of hepatic cysteinesulfinate decarboxylase, which converts cysteinesulfinate to hypotaurine. In incubations of either rat or cat hepatocytes with cysteine, no hypotaurine plus taurine production was detected. However, the 1-carbon of cysteine was converted to CO2 and the production of urea plus ammonia nitrogen was significantly increased over the rates observed in incubations of cells without substrate. Our results suggest that most cysteine oxidation by hepatocytes occurs by pathways that do not involve formation of cysteinesulfinate.

Effects of Microbial Inoculant on Fermentation of Alfalfa and Corn

Second cutting alfalfa (Medicago sativa L.), wilted to 45% dry matter, and whole plant corn (Zea mays L.; 40% dry matter) were mixed with a microbial inoculant, the inoculant carrier, or no additive and ensiled into 200-L steel drums. Addition of microbial inoculant at rate of 1kg additive/2,000kg wet forage resulted in approximately 7,000 to 10,000 viable anaerobes applied to each gram of wet forage. Microbial inoculation did not affect the following fermentation parameters: lactic and acetic acid production, pH decline, ammonia and nonprotein nitrogen production, or total and acid-tolerant anaerobe count in either forage. Forage pH declined faster and to a lower level in corn than in alfalfa, even though nearly twice as much acid was produced in alfalfa as in corn. Protein degradation, measured by ammonia and nonprotein nitrogen concentrations, was more extensive in alfalfa than corn. There was no difference in the total number of anaerobes between forage species; however, acid-tolerant anaerobes tended to increase with days ensiled for alfalfa but not for corn. It is possible that there are differences in the metabolic characteristics of microorganisms that develop in different forage species.

Ammonia-nitrogen production by the bivalve molluscTapes japonica and its recovery by the red seaweedHypnea musciformis in a tropical mariculture system

Production and recovery of ammonia-N was studied in the second and third trophic levels of a mariculture system on St. Croix, US Virgin Islands. The diatomChaetoceros curvisetus, grown on nutrients in artificially upwelled deep water from 870 m depth, was the food source forTapes japonica. Consumption of the phytoplankton byT. japonica increased throughout the day and decreased at night, and was related to corresponding changes in algal culture density. Feeding efficiency was highest at night. Ammonia-N production by the clams fluctuated over a typical 24 h period; dropping during the day and increasing at night. The ammonia-N concentration in the shellfish tank effluent was inversely related to the quantity of phytoplankton consumed by the clams. At all ration levels the small clams produced ammonia-N at a greater rate than large clams.H. musciformis fragmented and washed out of some tanks; the fragmentation was related to high ammonia-N concentrations in the inflowing water. High light intensity and temperature alone do not appear to cause fragmentation, but may have induced a trace nutrient deficiency inH. musciformis grown in the ammonia-rich seawater. Where fragmentation was not obvious, ammonia-N uptake per gH. musciformis was highly correlated with the average ammonia-N concentration of the inflowing seawater both day and night. Percent uptake of ammonia-N increased with increasing concentration of the nutrient in the inflowing seawater, reaching a plateau of about 70% uptake of the available ammonia-N at concentrations above 4 μg-at/l.

A Comparison of the All-Glass, Semipermeable Membrane, and Continuous Flow Types of Apparatus for In Vitro Rumen Fermentations1,2

Summary A comparison was made of three different types of apparatus commonly used for in vitro rumen fermentation studies. The types compared were the all-glass, the semipermeable membrane, and the continuous flow. Purified wood cellulose and several different types of hay were used as substrates, with cellulose digestion, total volatile fatty acid production, and ammonia nitrogen production (for the hay samples only) being used as criteria of microbial activity. No major differences were found between the different types of apparatus; however, the all-glass apparatus appears to be advantageous because of its simplicity.

Decomposition of forest litters

Studies have been made on the production of ammonia and nitrate nitrogen, rate of decomposition along with comparative changes in microbial population during decomposition of deciduous and coniferous litters. At the same time the effect of addition of antibiotics on the microbial population and rate of decomposition of coniferous litter was investigated. Liberation of nitrogen in the form of ammonia occurred somewhat more rapidly in decomposing deciduous litter than in that of the coniferous litter. Towards the end of the experiment the nitrification process commenced in the deciduous litter but was absent in the coniferous litter. The deciduous litter decomposed more rapidly than the coniferous litter. The bacteria and actinomycetes were consistently more numerous in the deciduous litter than in the coniferous litter; in the case of fungi the reverse occured. An antifungal antibiotic (cycloheximide) had little or no effect on numbers of fungi in the decomposing coniferous litter while antibacterial antibiotics (streptomycin and chloramphenicol) reduced slightly the numbers of bacteria and actinomycetes. Numbers of bacteria and actinomycetes were increased greatly in cultures receiving the antifungal antibiotic and fungal growth was apparently stimulated where antibacterial antibiotics were added. In spite of the observed shift in the microbial population brought about by the addition of antibiotics the rate of decomposition of the coniferous litter appeared to be unaffected. This would suggest that the type of microbia l population is not as important as the type of litter or some other factor in regard to decomposition rate.