@article{pradhan_hoover_clark_gumpertz_wollum_cobb_strock_2008, title={Septic tank additive impacts on microbial populations}, volume={70}, number={6}, journal={Journal of Environmental Health}, author={Pradhan, S. and Hoover, M. T. and Clark, G. H. and Gumpertz, M. and Wollum, A. G. and Cobb, C. and Strock, J.}, year={2008}, pages={22–27} }
 @article{li_allen_wollum_2004, title={Microbial biomass and bacterial functional diversity in forest soils: effects of organic matter removal, compaction, and vegetation control}, volume={36}, DOI={10.1016/j.soilbio.12.001}, number={4}, journal={Soil Biology & Biochemistry}, author={Li, Q. C. and Allen, Howard and Wollum, A. G.}, year={2004}, pages={571–579} }
 @article{bigelow_bowman_wollum_2002, title={Characterization of Soil Microbial Population Dynamics in Newly Constructed Sand‐Based Rootzones}, DOI={10.2135/cropsci2002.1611}, abstractNote={Modern sand‐based golf course putting greens are constructed for optimum soil physical properties. However, since they are sand based and synthetically prepared, it is often perceived that they support a less numerous and diverse microbial population than comparable native soils. This field study was conducted to monitor the microbial properties of five newly constructed sand‐based rootzone mixtures planted to creeping bentgrass ( Agrostis stolonifera var. palustris Huds. Farw.) during the first 2 yr of turfgrass establishment. Bacteria, fungi, actinomycetes, and aerobic spore forming ( Bacillus spp.) populations were determined on selective media. Nitrifiers and denitrifiers were estimated by a most probable number (MPN) technique. Within the first 6 mo after seeding, bacteria exceeded 10 8 cfu g −1 dry soil, similar to levels recorded in a mature sand‐based putting green. Bacteria were most numerous followed by actinomycetes, fungi, and Bacillus spp., respectively. Temporal changes in microbial populations were observed only in year one. The nitrogen transforming populations were numerically smaller (<10 4 cfu g −1 dry soil) than total bacteria but followed a similar temporal trend. Rootzone amendments had minimal effects on microbial properties but environmental factors and an actively growing turfgrass root system may have a greater influence on microbial activity.}, number={5}, journal={Crop Science}, author={Bigelow, Cale A. and Bowman, Daniel C. and Wollum, Arthur G.}, year={2002}, month={Sep} }
 @article{crouse_sierzputowska-gracz_mikkelsen_wollum_2002, title={Monitoring phosphorus mineralization from poultry manure using phosphatase assays and phosphorus-31 nuclear magnetic resonance spectroscopy}, volume={33}, DOI={10.1081/CSS-120003882}, abstractNote={Phosphatase enzymes are responsible for mineralization of organic-phosphorus (P) compounds in soil where they hydrolyze the organic phosphate esters to inorganic phosphate. One way to monitor the mineralization process in soils receiving poultry manure is by assessing the activity of phosphatase in a soil amended with poultry manure relative to a soil that is not amended. In a laboratory incubation, soil phosphomonoesterase activity and soil phosphodiesterase activity were measured 0, 1, 2, 4, 8, 12, 16, and 20 weeks after soil incorporation of poultry litter. Two soils, both Fine-loamy siliceous, thermic Typic Kandiudults, were used in the study. Both soils differed in their previous management. The first soil was from a conventionally tilled field that received annual poultry litter applications for 18 consecutive years. The second soil was from an adjacent recently cleared woodland that had no history of manure application. In the previously non-manured soil, soil phosphodiesterase activity following poultry litter addition increased from 4 to 66 μg p-nitrophenol g soil−1 hour−1 by the second week. However, in the same soil, after 8 weeks, phosphodiesterase activity resulting from poultry litter applications was not evident. There was a net increase in phosphomonoesterase activity from week 0 to 20 in the previously manured and previously non-manured soils that were amended with poultry litter. A simultaneous study was conducted to measure the relative concentration of organic P forms during the mineralization process using 31P nuclear magnetic resonance. Subsamples from the poultry manure-amended soil were extracted with 0.25 M NaOH+0.05 M EDTA following 0, 1, 2, 4, 8, 12, 16, and 20 weeks after manure addition and incorporation. The concentration of organic P compounds decreased from the time of poultry litter incorporation until week 20 whereas orthophosphate concentration increased during this period.}, number={7-8}, journal={Communications in Soil Science and Plant Analysis}, author={Crouse, D. A. and Sierzputowska-Gracz, H. and Mikkelsen, R. L. and Wollum, A. G.}, year={2002}, month={May}, pages={1205–1217} }
 @article{lee_wollum_bowman_peacock_rufty_2001, title={Temperature effects on nitrogen mineralization in bermudagrass turf}, volume={9}, journal={International Turfgrass Society Research Journal}, author={Lee, D. J. and Wollum, A. G. and Bowman, D. C. and Peacock, C. H. and Rufty, T. W., Jr.}, year={2001}, pages={394} }
 @article{vaughan_hoyt_wollum_2000, title={Cover crop nitrogen availability to conventional and no‐till corn: Soil mineral nitrogen, corn nitrogen status, and corn yield}, DOI={10.1080/00103620009370495}, abstractNote={Abstract Understanding seasonal soil nitrogen (N) availability patterns is necessary to assess corn (Zea mays L.) N needs following winter cover cropping. Therefore, a field study was initiated to track N availability for corn in conventional and no‐till systems and to determine the accuracy of several methods for assessing and predicting N availability for corn grown in cover crop systems. The experimental design was a systematic split‐split plot with fallow, hairy vetch (Vicia villosa Roth), rye (Secale cereale L.), wheat (Triticum aestivum L.), rye+hairy vetch, and wheat+hairy vetch established as main plots and managed for conventional till and no‐till corn (split plots) to provide a range of soil N availability. The split‐split plot treatment was sidedressed with fertilizer N to give five N rates ranging from 0–300 kg N ha‐1 in 75 kg N ha‐1 increments. Soil and corn were sampled throughout the growing season in the 0 kg N ha‐1 check plots and corn grain yields were determined in all plots. Plant‐available N was greater following cover crops that contained hairy vetch, but tillage had no consistent affect on N availability. Corn grain yields were higher following hairy vetch with or without supplemental fertilizer N and averaged 11.6 Mg ha‐1 and 9.9 Mg ha‐1 following cover crops with and without hairy vetch, respectively. All cover crop by tillage treatment combinations responded to fertilizer N rate both years, but the presence of hairy vetch seldom reduced predicted fertilizer N need. Instead, hairy vetch in monoculture or biculture seemed to add to corn yield potential by an average of about 1.7 Mg ha‐1 (averaged over fertilizer N rates). Cover crop N contributions to corn varied considerably, likely due to cover crop N content and C:N ratio, residue management, climate, soil type, and the method used to assess and assign an N credit. The pre‐sidedress soil nitrate test (PSNT) accurately predicted fertilizer N responsive and N nonresponsive cover crop‐corn systems, but inorganic soil N concentrations within the PSNT critical inorganic soil N concentration range were not detected in this study.}, number={7-8}, journal={Communications in Soil Science and Plant Analysis}, author={Vaughan, Jeffrey D. and Hoyt, Greg D. and Wollum, Arthur G.}, year={2000}, month={Apr} }
 @article{hilger_wollum_barlaz_2000, title={Landfill Methane Oxidation Response to Vegetation, Fertilization, and Liming}, volume={29}, DOI={10.2134/jeq2000.00472425002900010041x}, abstractNote={Abstract This study was conducted to evaluate the effects of vegetation, N fertilizers, and lime addition on landfill CH 4 oxidation. Columns filled with compacted sandy loam and sparged with synthetic landfill gas were used to simulate a landfill cover. Grass‐topped and bare‐soil columns reduced inlet CH 4 by 47 and 37%, respectively, at peak uptake; but the rate for both treatments was about 18% at steady slate. Nitrate and NH 4 amendments induced a more rapid onset of CH 4 oxidation relative to KCl controls. However, at steady state, NH 4 inhibited CH 4 oxidation in bare columns but not in grassed columns. Nitrate addition produced no inhibitory effects. Lime addition to the soil consistently enhanced CH 4 oxidation. In all treatments, CH 4 consumption increased to a peak value, then declined to a lower steady‐state value; and all gassed columns developed a pH gradient. Neither nutrient depletion nor protozoan grazing could explain the decline from peak oxidation levels. Ammonium applied to grassed cover soil can cause transient reductions in CH 4 uptake, but there is no evidence that the inhibition persists. The ability of vegetation to mitigate NH 4 inhibition indicates that results from bare‐soil tests may not always generalize to vegetated landfill caps.}, number={1}, journal={Journal of Environmental Quality}, author={Hilger, Helene A. and Wollum, Arthur G. and Barlaz, Morton A.}, year={2000}, month={Jan}, pages={324–334} }
 @article{wollum_a. g._1998, title={Constraints and opportunities for biological nitrogen fixation in a changing world}, ISBN={0908307586}, journal={Harnessing biological nitrogen fixation in African agriculture : challenges and opportunities : Sixth International Conference of the African Association for Biological Nitrogen Fixation, 12-17 September, 1994, Harare, Zimbabwe : selected papers}, publisher={Mount Pleasant, Harare, Zimbabwe : University of Zimbabwe Publications}, author={Wollum and A. G.}, editor={S. M. Mpepereki and Makonese, F. T.Editors}, year={1998}, pages={11} }
 @article{keller_weber_cassel_wollum_miller_1998, title={TEMPORAL DISTRIBUTION OF 14C IN SOIL WATER FROM FIELD LYSIMETERS TREATED WITH 14C-METOLACHLOR}, DOI={10.1097/00010694-199811000-00004}, abstractNote={In a previous study utilizing fallow field lysimeters of an undisturbed, loamy sand soil treated with 14C-metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide], 2 to 5% of the applied 14C was mobile to soil depths of 56 to 96 cm. The objective of this 120-day study was to determine the temporal distribution of 14C-metolachlor and/or metabolite(s) in soil water from similar field lysimeters and their possible contribution to groundwater contamination. Undisturbed soil column field lysimeters (20.3-cm i.d. × 101-cm long; 16 gauge steel) were driven into a conventionally tilled Dothan loamy sand (fine-loamy, siliceous, thermic Plinthic Kandiudult) and treated with 14C-metolachlor and tritiated water (3H2O) and subjected to natural rainfall or irrigation. Percent recovery of metolachlor and/or metabolite(s) in the soil, as based on 14C measurement, was 62% at 30 days, 63% at 60 days, 51% at 90 days, and 49% at 120 days. Recovery of 3H2O was 36, 24, 6 and 0.25% of the applied for the same time periods. By 30 and 60 days after application (DAA), 3H2O had distributed symmetrically in the soil profile, whereas, a large percentage of the 14C was retained in the upper 24 cm. No 14C and <1% of the applied 3H2O was recovered in leachate the first 30 days. Cumulative recovery of 14C in leachate was <1% of that applied at 60 days, 3% at 90 days, and 7% at 120 days. Cumulative recovery of 3H2O in leachate for the same time periods was 22, 39, and 39% of that applied. The symmetrical breakthrough curve for 3H2O indicated no preferential flow or immobile water, whereas the breakthrough curve for 14C was asymmetrical as a result of the sorption-desorption processes. Peak concentrations of 14C and 3H2O in the leachate occurred at 94 and 63 DAA, respectively. The sorptive tendencies of both radiolabeled species distinguished the magnitude of movement, with 3H2O much more mobile than 14C-metolachlor and/or metabolite(s). Assuming that all 14C in leachate was parent, average metolachlor concentrations in leachate were less than the National Health Advisory level, which may indicate that metolachlor should be considered a low risk chemical because of its potential to contaminate groundwater in soils with low organic matter and high clay content in the subsoil.}, number={11}, journal={Soil Science}, author={Keller, K. E. and Weber, J. B. and Cassel, D. K. and Wollum, A. G. and Miller, C. T.}, year={1998}, month={Nov} }
 @article{ramirez_israel_wollum_1998, title={Using spontaneous antibiotic-resistant mutants to assess competitiveness of bradyrhizobial inoculants for nodulation of soybean}, DOI={10.1139/cjm-44-8-753}, abstractNote={Spontaneous mutants (3/parental strain) of soybean bradyrhizobia resistant to streptomycin and erythromycin were selected from strains isolated from bradyrhizobial populations indigenous to Cape Fear and Dothan soils. These were used to evaluate (i) the validity of using antibiotic-resistant mutants to make inferences about the competitiveness of parental strains in soil environments and (ii) the recovery of strains in nodules after inoculation of soybeans grown in soils with indigenous bradyrhizobial populations. Streptomycin and erythromycin resistances of all mutants were stable after approximately 27 generations of growth in yeast extract - mannitol medium, but 33% of the mutants lost resistance to erythromycin upon passage through nodules. Only 17% of the mutants were as competitive as their parental strain when inoculated in a ratio near 1:1 in vermiculite. Four of 10 mutants, which differed in competitiveness from their parental strain in vermiculite, had competitiveness against the soil populations equal to that of their parental strain. Therefore, assessment of competitiveness of mutants and parental strains in non-soil media may not accurately reflect their competitiveness in soil systems. For both the Cape Fear and Dothan soils, recovery of a given mutant from nodules of field-grown plants was always lower than from nodules of plants grown in the greenhouse. Inoculation of the entire rooting zone in the greenhouse experiment and of only a portion of the rooting zone in the field experiments may account for this difference in recovery. Techniques that increase the volume of soil inoculated may enhance nodulation by inoculant strains.Key words: Bradyrizobium, antibiotic resistance, competition.}, number={8}, journal={Canadian Journal of Microbiology}, author={Ramirez, Martha E. and Israel, Daniel W. and Wollum, Arthur G., II}, year={1998}, month={Jan} }
 @article{surange_wollum_kumar_nautiyal_1997, title={Characterization of <i>Rhizobium</i> from root nodules of leguminous trees growing in alkaline soils}, DOI={10.1139/m97-130}, abstractNote={High temperature, pH, and salt stresses in tropical alkaline soils limit nodulation and dinitrogen fixation by strains of Rhizobium from the root nodules of nitrogen fixing trees (NFTs). This study was conducted to determine the variability among Rhizobium strains isolated from different NFTs in growth response to high temperature, pH, and salt concentrations. Variable response to increases in temperature, pH, and salt concentrations was observed. Rhizobium strain isolated from Albizia lebbek survived at 50 °C, while Rhizobium strains isolated from Sesbania formosa, Acacia farnesiana, and Dalbergia sissoo were well adapted to grow on pH 12.0. All the Rhizobium strains tolerated salt concentrations up to 5.0%. Strains were further characterized with respect to utilization of 27 carbon sources and for their effectiveness in substrate utilization at pH 7.0 and 9.0. Generally higher rates of O 2 consumption were observed at pH 7.0 compared with pH 9.0.Key words: Rhizobium, leguminous trees, root nodules, stress tolerance.}, number={9}, journal={Canadian Journal of Microbiology}, author={Surange, S. and Wollum, A. G., II and Kumar, N. and Nautiyal, C. Shekhar}, year={1997}, month={Sep} }
 @article{miller_wollum_weber_1997, title={Degradation of Carbon‐14‐Atrazine and Carbon‐14‐Metolachlor in Soil from Four Depths}, DOI={10.2134/jeq1997.00472425002600030007x}, abstractNote={Abstract Degradation of 14 C‐atrazine [2‐chloro‐4‐ethylamino‐6‐isopropylamino‐ s ‐triazine] and 14 C‐metolachlor [2‐chloro‐ N ‐(2‐ethyl‐6‐methylphenyl)‐ N ‐(2‐methoxy‐1‐methylethyl) acetamide] was monitored for 6 and 2 mo, respectively, using sterile and nonsterile soil microcosms. Both chemical and biological degradation were observed for atrazine, metolachlor degraded only biologically. The calculated halflife of atrazine was 3.6 wk in nonsterile surface samples (0–5 cm). At the surface, after 22 wk, bound residues accounted for almost 60% of the recovered radioactivity while 36% was recovered as 14 CO 2 , indicating significant cleavage of the triazine ring. For sterilized surface samples, atrazine degraded chemically with bound residues accounting for 63% of the recovered label and had a calculated halflife of 6.2 wk. Degradation and binding were somewhat lower in soil samples from 20 to 25 cm and deeper subsurface samples (45 and 75 cm) showed almost no degradation and very little binding. Metolachlor degraded only in the surface nonsterile samples; no degradation was observed in subsurface samples or in sterile samples from any depth. Bound residues occurred in high amounts in the surface soil (31%) but declined rapidly with depth, indicating that organic matter is the primary binding site for metolachlor. Very little 14 CO 2 (<1.6%) was produced from metolachlor in any sample. This study showed that both herbicides degraded slower and sorbed less to the soil with increasing soil depth, especially below 25 cm. Quantifying degradation rates of agricultural chemicals in the vadose zone is important for predicting and preventing groundwater contamination as well as for successful implementation of in‐situ bioremediation of contaminated subsoils.}, number={3}, journal={Journal of Environmental Quality}, author={Miller, J. L. and Wollum, A. G. and Weber, J. B.}, year={1997}, month={May} }
 @article{ramirez_israel_wollum_1997, title={Phenotypic and genotypic diversity of similar serotypes of soybean bradyrhizobia from two soil populations}, DOI={10.1016/S0038-0717(97)00009-6}, abstractNote={The physiological and genetic diversity within two major serotypic groups of bradyrhizobial isolates obtained from soybean (Glycine max L. Merr.) plants grown on a Dothan and a Cape Fear soil was examined. All isolates serotyped as 3194 had large colonies with smooth borders and high resistances to erythromycin, streptomycin and spectinomycin with minimal inhibitory concentration values (MIC) ranging from 200 to 400 μg ml−1. Pulsed-field gel-electrophoresis (PFGE) separation of DNA fragments generated with the rarely cutting restriction endonuclease, Xba I, revealed six genotypes among 28 different 3194 isolates. Four of these genotypes were common to both soils and only 21% of the isolates were classified as having high N2-fixation capacity. Leaf chlorosis was induced by 46% of the 3194 isolates. Among the 122124 isolates, MIC values were lower than for 3194 isolates ranging from < 13 to 200 μg ml−1. These 122124 isolates produced small colonies (50%) and large colonies with rough borders (50%) when plated on YEM. The genetic diversity of serotype 122124 isolates differed with soil type as PFGE patterns revealed nine genotypes among the 16 isolates from the mineral organic (Cape Fear) soil and only three genotypes among the 14 isolates from the sandy mineral (Dothan) soil. Only two of the 12 genotypes were common to both soils. Sixty percent of the 122124 isolates were classified as having high N2-fixation capacity and none induced foliar chlorosis. Pulsed-field gel-electrophoresis pattern was the only trait that generated groups of isolates that were similar with respect to other measured traits.}, number={9-10}, journal={Soil Biology and Biochemistry}, author={Ramirez, Martha E. and Israel, Daniel W. and Wollum, A.G.}, year={1997}, month={Sep} }
 @article{ramirez_israel_wollum_1997, title={Phenotypic characterization of soybean bradyrhizobia in two soils of North Carolina}, DOI={10.1016/S0038-0717(97)00008-4}, abstractNote={Serotypic composition of nodules (480 per soil type) from five soybean cultivars grown on two (Dothan and Cape Fear) soils of the Atlantic Coastal Plain of North Carolina was characterized. Symbiotic N2-fixation efficiency, capacity for induction of foliar chlorosis symptomatic of rhizobitoxine production and antibiotic resistances of isolates purified from these nodules were also determined. While host plant cultivar had no significant effect on the serotype distribution, soil type had a large effect on the distribution and diversity of serotypes. Forty-six serotypes were identified among nodules from the Cape Fear soil, but only serotype 4676 (8%), 76 (11%), 94 (9%) and 122124 (12%) occurred in more than 5% of the nodules. Thirty percent of nodule occupants were not identified with the eleven antisera used. Twenty-four serotypes were identified among nodules from the Dothan soil. Of these serotypes 3194 (32%), 4676 (16%), and 76 (23%) occurred in more than 15% of the nodules. Five percent of the nodule occupants were not identified. Major serotypes did not change, but their frequency changed when fields were sampled at different growth stages in the same season and at the same growth stage in different seasons. Isolates serotyped as 3194, 4676, and most of the isolates serotyped as 76 generally exhibited higher levels of resistance to streptomycin and erythromycin than isolates serotyped as 24, 94 and 122124. Five percent of the isolates from the Cape Fear soil (all serotyped as 3194) and 18% of the isolates from the Dothan soil (serotyped as 3194 or 76) induced foliar chlorosis when cultivar Brim was the host. Only 12–14% of the isolates from the two populations had N2-fixation capacity equal to or greater than that of the efficient reference strain MN110. However, four improved soybean cultivars grown in the same fields and year that isolates were obtained did not exhibit a significant seed yield response to application of 150 kg N ha−1 when yields in the minus N treatment ranged from 3.2 to 3.7 Mg ha−1. A significant seed yield response by a non-nodulated cultivar indicated that these soils were N limited. Therefore, the symbiotic N2-fixation capacity of these bradyrhizobial populations did not limit soybean seed yields despite the low percentage of isolates with high N2-fixation efficiency and the presence of isolates with the capacity to induce leaf chlorosis symptomatic of rhizobitoxine production.}, number={9-10}, journal={Soil Biology and Biochemistry}, author={Ramirez, Martha E. and Israel, Daniel W. and Wollum, A.G.}, year={1997}, month={Sep} }
 @article{mpepereki_makonese_wollum_1997, title={Physiological characterization of indigenous rhizobia nodulating Vigna unguiculata in Zimbabwean soils}, volume={22}, number={3}, journal={Symbiosis}, author={Mpepereki, S. and Makonese, F. and Wollum, A. G.}, year={1997}, pages={275–292} }
 @article{miller_wollum_weber_1997, title={Sterile and Nonsterile Degradation of Carbon‐14‐Primisulfuron in Soil from Four Depths}, DOI={10.2134/jeq1997.00472425002600020015x}, abstractNote={Abstract The degradation of 14 C‐primisulfuron (2‐[[[[[4,6‐bis(difluoromethoxy)‐2‐pyrimidinyl]amino]carbonyl]amino]sulfonyl] benzoic acid) was monitored for 2 mo using soil microcosms under sterile and nonsterile conditions. Both chemical and biological degradation was detected. The half‐life was 2.1 wk for nonsterile samples from 0 to 5 cm, and 3.4 wk for nonsterile samples from 20 to 25 cm. After 7 wk, bound residues accounted for 48 and 27% of the recovered radioactivity in these samples, respectively. For sterile samples from the same depths, the half‐life was >7 wk and bound residues accounted for 7% of the recovered radiolabel. Disappearance and bound residue formation of primisulfuron were similar for both sterile and nonsterile samples from deeper in the profile (45–75 cm) indicating little biological degradation occurred in these subsurface samples. Chemical and microbial degradation of primisulfuron appeared to differ; the same metabolites were produced but at different times and in different amounts. Very little 14 CO 2 (<3%) was produced from any sample. These results indicate that initial hydrolyzation of the sulfonylurea bridge occurs both chemically and biologically, but does not occur readily in the subsoil. This may have implications for the prevention of groundwater contamination and for the bioremediation of contaminated soils.}, number={2}, journal={Journal of Environmental Quality}, author={Miller, J. L. and Wollum, A. G. and Weber, J. B.}, year={1997}, month={Mar} }
 @inbook{wollum_a. g._1982, title={Cultural methods for soil microorganisms}, ISBN={089118810X}, booktitle={Methods of soil analysis. Part 2, Microbiological and biochemical properties}, publisher={American Society of Agronomy, Soil Science Society of America}, author={Wollum and A. G.}, year={1982}, pages={781} }