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Arkansas Agricultural Experiment Station

facilityArkansas City, Arkansas, United States

Research output, citation impact, and the most-cited recent papers from Arkansas Agricultural Experiment Station (United States). Aggregated across the NobleBlocks index of 300M+ scholarly works.

Total works
13.3K
Citations
436.2K
h-index
194
i10-index
9.5K
Also known as
Arkansas Agricultural Experiment Station

Top-cited papers from Arkansas Agricultural Experiment Station

DETERMINATION OF TOTAL, ORGANIC, AND AVAILABLE FORMS OF PHOSPHORUS IN SOILS
R. H. Bray, L. T. Kurtz
1945· Soil Science7.6Kdoi:10.1097/00010694-194501000-00006

Illinois Agricultural Experiment Station 2 Chief and associate, soil fertility, department of agronomy, respectively.

Stage of Development Descriptions for Soybeans, <i>Glycine Max</i> (L.) Merrill<sup>1</sup>
W. R. Fehr, C. E. Caviness, Dwayne Thomas Burmood, J. S. Pennington
1971· Crop Science2.9Kdoi:10.2135/cropsci1971.0011183x001100060051x

We developed stage of development descriptions which we believe apply to all soybean ( Glycine max (L.) Merr.) genotypes grown in any environment. The descriptions apply to single plants or a community of plants and are precise and objective. Vegetative and reproductive development are described separately. Vegetative stages are determined by counting the number of nodes on the main stem, beginning with the unifoliolate node, that have or have had a completely unrolled leaf. Reproductive stages Rl and R2 are based on flowering, R3 and R4 on pod development, R5 and R6 on seed development, and R7 and R8 on maturation. The stage descriptions should enhance soybean research by standardizing descriptions of soybean plant development. The system also will be used by the soybean hail insurance industry for stage determination in adjustment of losses.

AUTOMATED METHODS FOR ESTIMATING BASEFLOW AND GROUND WATER RECHARGE FROM STREAMFLOW RECORDS<sup>1</sup>
Jeffrey G. Arnold, Peter M. Allen
1999· JAWRA Journal of the American Water Resources Association810doi:10.1111/j.1752-1688.1999.tb03599.x

ABSTRACT: To quantify and model the natural ground water recharge process, six sites located in the midwest and eastern United States where previous water balance observations had been made were compared to computerized techniques to estimate: (1) base flow and (2) ground water recharge. Results from an existing automated digital filter technique for separating baseflow from daily streamflow records were compared to baseflow estimates made in the six water balance studies. Previous validation of automated baseflow separation techniques consisted only of comparisons with manual techniques. In this study, the automated digital filter technique was found to compare well with measured field estimates yielding a monthly coefficient of determination of 0.86. The recharge algorithm developed in this study is an automated derivation of the Rorabaugh hydrograph recession curve displacement method that utilizes daily streamflow. Comparison of annual recharge from field water balance measurements to those computed with the automated recession curve displacement method had coefficients of determination of 0.76 and predictive efficiencies of 71 percent. Monthly estimates showed more variation and are not advocated for use with this method. These techniques appear to be fast, reproducible methods for estimating baseflow and annual recharge and should be useful in regional modeling efforts and as a quick check on mass balance techniques for shallow water table aquifers.

THE ORIGIN OF TRITICUM SPELTA AND ITS FREE-THRESHING HEXAPLOID RELATIVES*
E. S. McFadden, E. R. Sears
1946· Journal of Heredity808doi:10.1093/oxfordjournals.jhered.a105590

Journal Article THE ORIGIN OF TRITICUM SPELTA AND ITS FREE-THRESHING HEXAPLOID RELATIVES Get access E. S. MCFADDEN, E. S. MCFADDEN †Associate Agronomist, U. S. Department of Agriculture, Texas Agricultural Experiment Station. College StationTexas Search for other works by this author on: Oxford Academic PubMed Google Scholar E. R. SEARS E. R. SEARS ‡Senior Geneticist. U. S. Department of Agriculture, Genetics Building, University of MissouriColumbia, Missouri Search for other works by this author on: Oxford Academic PubMed Google Scholar Journal of Heredity, Volume 37, Issue 3, March 1946, Pages 81–89, https://doi.org/10.1093/oxfordjournals.jhered.a105590 Published: 01 March 1946

DETERMINATION OF EXCHANGE CAPACITY AND EXCHANGEABLE BASES IN SOIL—AMMONIUM ACETATE METHOD
C. J. Schollenberger, R. H. Simon
1945· Soil Science807doi:10.1097/00010694-194501000-00004

DETERMINATION OF EXCHANGE CAPACITY AND EXCHANGEABLE BASES IN SOIL—AMMONIUM ACETATE METHOD C. SCHOLLENBERGER;R. SIMON; Soil Science

Urea and Guanidine Hydrochloride Denaturation of Ribonuclease, Lysozyme, α-Chymotrypsin, and b-Lactoglobulin
Raymond F. Greene, C. Nick Pace
1974· Journal of Biological Chemistry805doi:10.1016/s0021-9258(20)79739-5

Goat P-lactoglobulin was prepared from the milk of two Saanen goats by the procedure of Kalan and Basch (12).

Designing sorghum as a dedicated bioenergy feedstock
William L. Rooney, Jürg M. Blumenthal, Brent Bean, John E. Mullet
2007· Biofuels Bioproducts and Biorefining716doi:10.1002/bbb.15

Abstract The increasing cost of energy and finite oil and gas reserves has created a need to develop alternative fuels from renewable sources. Currently, the development of a renewable transportation fuel is ethanol based. Ethanol production is now sugar/starch based, but use of these carbohydrates is limited; they are also required as a food and feed source. The need to generate a large and sustainable supply of biomass to make biofuels generation from lignocellulose profitable will require the development of crops grown specifically for bioenergy production. There will be several different species used as dedicated bioenergy crops, and for several reasons; it is expected that sorghum ( Sorghum bicolor L. Moench) will be one of these species. Sorghum is a highly productive, drought‐tolerant species with a history of improvement and production of lignocellulose, sugar and starch. Given this history and the existing genetic improvement infrastructure available for the species, it is logical to expect that sorghum hybrids for dedicated bioenergy production can be developed in the near‐term future and will be grown and used for bioenergy production. © 2007 Society of Chemical Industry and John Wiley &amp; Sons, Ltd

Changes in Phytochemical and Antioxidant Activity of Selected Pepper Cultivars (<i>Capsicum </i>Species) As Influenced by Maturity
Luke R. Howard, Stephen T. Talcott, C. H. Brenes, B. Villalón
2000· Journal of Agricultural and Food Chemistry664doi:10.1021/jf990916t

The effect of fruit maturation on changes in carotenoids, flavonoids, total soluble reducing equivalents, phenolic acids, ascorbic acid, and antioxidant activity (AOX) in different pepper types (Capsicum annuum, Capsicum frutescens, and Capsicum chinese) was determined. Generally, the concentration of these chemical constituents increased as the peppers reached maturity. Peppers contained high levels of L-ascorbic acid and carotenoids at maturity, contributing 124-338% of the RDA for vitamin C and 0.33-336 RE/100 g of provitamin A activity, respectively. Levels of phenolic acids, capxanthin, and zeaxanthin generally increased during maturation, whereas the level of lutein declined. Flavonoid concentrations varied greatly among the pepper types analyzed and were negatively correlated to AOX under the conditions of the beta-carotene-linoleic assay. Model systems were used to aid in understanding the relationship between flavonoids and AOX. Significant increases in AOX were observed in pepper juice models in response to increasing dilution factors and the presence of EDTA, indicating a pro-oxidant effect due to metal ions in the system. In vitro models demonstrated that increasing levels of flavonoids in combination with constant levels of caffeic and ascorbic acid gave a resultant AOX that was either additive of the two compounds or competitive in their ability to scavenge peroxyl radicals. The model systems were in good agreement with the chemical composition of the pepper cultivars and reflected the interactions affecting AOX. More research is needed to understand the complex interactions that occur among various antioxidants present in pepper extracts.

The Nomenclature and Classification of the Actinomycetes
Selman A. Waksman, Arthur T. Henrici
1943· Journal of Bacteriology628doi:10.1128/jb.46.4.337-341.1943

The exact position of the actinomycetes or ray-fungi in the kingdom of lower forms of life has attracted considerable atten-tion and has been a subject of much speculation. These organ-isms have been classified as bacteria, as fungi, and as a special group, either derived from one of the above or giving rise to both. With the accumulated knowledge concerning the morphology of the actinomycetes, it is being recognized more and more that they are an independent group of organisms, which is closely related to the bacteria through some of the constituent forms, but which has adopted a fungus-like form of growth. A brief description of the mode of growth and spore formation of these organisms will suffice to indicate their exact taxonomic position. Actinomycetes are characterized by the formation of normally branching threads or rods, frequently giving rise to a typical mycelium which is unicellular, especially during the early stages of growth. The hyphae are generally non-septate; under certain special conditions, septa may be observed in some forms. The mycelium is either vegetative and growing in the substrate, or aerial, where a special mycelium is produced above the vegetative growth. Actinomycetes reproduce through special sporulating bodies or from parts of the vegetative mycelium. The spore-bearing hyphae are produced on the mycelium either singly and monopodially, or in broom-like or cluster-like formations, or in verticilliate-like tufts or whorls upon the mycelium. The sporo-phores vary from long to very short forms. The spores may also

Polymicrobial Nature of Chronic Diabetic Foot Ulcer Biofilm Infections Determined Using Bacterial Tag Encoded FLX Amplicon Pyrosequencing (bTEFAP)
Scot E. Dowd, Randall D. Wolcott, Yan Sun, Trevor McKeehan +2 more
2008· PLoS ONE556doi:10.1371/journal.pone.0003326

BACKGROUND: Diabetic extremity ulcers are associated with chronic infections. Such ulcer infections are too often followed by amputation because there is little or no understanding of the ecology of such infections or how to control or eliminate this type of chronic infection. A primary impediment to the healing of chronic wounds is biofilm phenotype infections. Diabetic foot ulcers are the most common, disabling, and costly complications of diabetes. Here we seek to derive a better understanding of the polymicrobial nature of chronic diabetic extremity ulcer infections. METHODS AND FINDINGS: Using a new bacterial tag encoded FLX amplicon pyrosequencing (bTEFAP) approach we have evaluated the bacterial diversity of 40 chronic diabetic foot ulcers from different patients. The most prevalent bacterial genus associated with diabetic chronic wounds was Corynebacterium spp. Findings also show that obligate anaerobes including Bacteroides, Peptoniphilus, Fingoldia, Anaerococcus, and Peptostreptococcus spp. are ubiquitous in diabetic ulcers, comprising a significant portion of the wound biofilm communities. Other major components of the bacterial communities included commonly cultured genera such as Streptococcus, Serratia, Staphylococcus and Enterococcus spp. CONCLUSIONS: In this article, we highlight the patterns of population diversity observed in the samples and introduce preliminary evidence to support the concept of functional equivalent pathogroups (FEP). Here we introduce FEP as consortia of genotypically distinct bacteria that symbiotically produce a pathogenic community. According to this hypothesis, individual members of these communities when they occur alone may not cause disease but when they coaggregate or consort together into a FEP the synergistic effect provides the functional equivalence of well-known pathogens, such as Staphylococcus aureus, giving the biofilm community the factors necessary to maintain chronic biofilm infections. Further work is definitely warranted and needed in order to prove whether the FEPs concept is a viable hypothesis. The findings here also suggest that traditional culturing methods may be extremely biased as a diagnostic tool as they select for easily cultured organisms such as Staphylococcus aureus and against difficult to culture bacteria such as anaerobes. While PCR methods also have bias, further work is now needed in comparing traditional culture results to high-resolution molecular diagnostic methods such as bTEFAP.

Genetic Management of Fragmented Animal and Plant Populations
Richard Frankham, Jonathan D. Ballou, Katherine Ralls, Mark D. B. Eldridge +4 more
2017519doi:10.1093/oso/9780198783398.001.0001

Abstract The biological diversity of the planet is being rapidly depleted due to the direct and indirect consequences of human activity. As the size of animal and plant populations decrease and fragmentation increases, loss of genetic diversity reduces their ability to adapt to changes in the environment, with inbreeding and reduced fitness inevitable consequences for many species. Many small isolated populations are going extinct unnecessarily. In many cases, such populations can be genetically rescued by gene flow into them from another population within the species, but this is very rarely done. This novel and authoritative book addresses the issues involved in genetic management of fragmented animal and plant populations, including inbreeding depression, loss of genetic diversity and elevated extinction risk in small isolated populations, augmentation of gene flow, genetic rescue, causes of outbreeding depression and predicting its occurrence, desirability and implementation of genetic translocations to cope with climate change, and defining and diagnosing species for conservation purposes.

Review of some aspects of growth and development of feedlot cattle.
F. N. Owens, D. R. Gill, D S Secrist, S. W. Coleman
1995· Journal of Animal Science492doi:10.2527/1995.73103152x

Growth in animals is defined as accretion of protein, fat and bone. Although growth typically is measured as the change in live weight, nutrient retention is estimated more precisely by measuring empty body weight and composition, whereas production economics are measured ideally through carcass weights and quality. As a percentage of live weight gain, carcass weight gain usually is a much higher percentage during the feedlot phase than during the growing phase of production because dressing percentage (ratio of carcass:live weight) increases with maturation and is greater with concentrate than with roughage diets. At a given fraction of mature body size (maximum body protein mass), body fat percentage seems to be a constant. Mature size may be altered genetically and nutritionally. Protein accretion declines to zero when cattle reach their mature body size (approximately 36% fat in empty body weight in modern cattle) even though mature animals can continue to accrete fat. Although fat accretion can be reduced by limiting the supply of net energy, rate of fat accretion by finishing steers given ad libitum access to high-concentrate diets seems to reach a plateau at approximately 550 g daily. Protein mass, in contrast, increases in proportion to empty body weight. The protein:fat ratio of the carcass can be increased through increasing mature size, by administering hormones or hormonal modifiers, by limiting energy intake during the growing period or finishing period, or by slaughtering cattle at an earlier stage of maturity. Energetically, efficiency of accretion of fat is approximately 1.7 times that of protein. But because more water is stored with deposited protein than with deposited fat, lean tissue gain is four times as efficient as accretion of fat tissue. Conversion of protein to fat is very inefficient, suggesting that excess protein is utilized inefficiently.

A Compositional Look at the Human Gastrointestinal Microbiome and Immune Activation Parameters in HIV Infected Subjects
Ece Mutlu, Ali Keshavarzian, John Losurdo, Garth Swanson +4 more
2014· PLoS Pathogens474doi:10.1371/journal.ppat.1003829

HIV progression is characterized by immune activation and microbial translocation. One factor that may be contributing to HIV progression could be a dysbiotic microbiome. We therefore hypothesized that the GI mucosal microbiome is altered in HIV patients and this alteration correlates with immune activation in HIV. 121 specimens were collected from 21 HIV positive and 22 control human subjects during colonoscopy. The composition of the lower gastrointestinal tract mucosal and luminal bacterial microbiome was characterized using 16S rDNA pyrosequencing and was correlated to clinical parameters as well as immune activation and circulating bacterial products in HIV patients on ART. The composition of the HIV microbiome was significantly different than that of controls; it was less diverse in the right colon and terminal ileum, and was characterized by loss of bacterial taxa that are typically considered commensals. In HIV samples, there was a gain of some pathogenic bacterial taxa. This is the first report characterizing the terminal ileal and colonic mucosal microbiome in HIV patients with next generation sequencing. Limitations include use of HIV-infected subjects on HAART therapy.

Triazoles as Plant Growth Regulators and Stress Protectants
R. A. Fletcher, Angela Gilley, N. Sankhla, Tim D. Davis
1999· Horticultural reviews447doi:10.1002/9780470650776.ch3

This chapter contains sections titled: Introduction Translocation and Efficacy of Application Methods General Plant Responses to Triazoles Mode of Action Stress Protection Potential and Current Applications A Novel Seed Treatment Technology Summary Literature Cited

LARGE AREA HYDROLOGIC MODELING AND ASSESSMENT PART II: MODEL APPLICATION<sup>1</sup>
Raghavan Srinivasan, Tharacad Ramanarayanan, Jeffrey G. Arnold, Steven T. Bednarz
1998· JAWRA Journal of the American Water Resources Association446doi:10.1111/j.1752-1688.1998.tb05962.x

ABSTRACT: This paper describes the application of a river basin scale hydrologic model (described in Part I) to Richland and Chambers Creeks watershed (RC watershed) in upper Trinity River basin in Texas. The inputs to the model were accumulated from hydro‐graphic and geographic databases and maps using a raster‐based GIS. Available weather data from 12 weather stations in and around the watershed and stream flow data from two USGS stream gauge station for the period 1965 to 1984 were used in the flow calibration and validation. Sediment calibration was carried out for the period 1988 through 1994 using the 1994 sediment survey data from the Richland‐Chambers lake. Sediment validation was conducted on a subwatershed (Mill Creek watershed) situated on Chambers Creek of the RC watershed. The model was evaluated by well established statistical and visual methods and was found to explain at least 84 percent and 65 percent of the variability in the observed stream flow data for the calibration and validation periods, respectively. In addition, the model predicted the accumulated sediment load within 2 percent and 9 percent from the observed data for the RC watershed and Mill Creek watershed, respectively.

Massive parallel 16S rRNA gene pyrosequencing reveals highly diverse fecal bacterial and fungal communities in healthy dogs and cats
Stefanie Handl, Scot E. Dowd, José F. García-Mazcorro, Jörg M. Steiner +1 more
2011· FEMS Microbiology Ecology440doi:10.1111/j.1574-6941.2011.01058.x

This study evaluated the fecal microbiota of 12 healthy pet dogs and 12 pet cats using bacterial and fungal tag-encoded FLX-Titanium amplicon pyrosequencing. A total of 120,406 pyrosequencing reads for bacteria (mean 5017) and 5359 sequences (one pool each for dogs and cats) for fungi were analyzed. Additionally, group-specific 16S rRNA gene clone libraries for Bifidobacterium spp. and lactic acid-producing bacteria (LAB) were constructed. The most abundant bacterial phylum was Firmicutes, followed by Bacteroidetes in dogs and Actinobacteria in cats. The most prevalent bacterial class in dogs and cats was Clostridia, dominated by the genera Clostridium (clusters XIVa and XI) and Ruminococcus. At the genus level, 85 operational taxonomic units (OTUs) were identified in dogs and 113 OTUs in cats. Seventeen LAB and eight Bifidobacterium spp. were detected in canine feces. Ascomycota was the only fungal phylum detected in cats, while Ascomycota, Basidiomycota, Glomeromycota, and Zygomycota were identified in dogs. Nacaseomyces was the most abundant fungal genus in dogs; Saccharomyces and Aspergillus were predominant in cats. At the genus level, 33 different fungal OTUs were observed in dogs and 17 OTUs in cats. In conclusion, this study revealed a highly diverse bacterial and fungal microbiota in canine and feline feces.

The effect of grain source and grain processing on performance of feedlot cattle: a review.
F. N. Owens, D S Secrist, W. J. Hill, D. R. Gill
1997· Journal of Animal Science436doi:10.2527/1997.753868x

Effects of grain species and grain processing method on DMI, rate and efficiency of gain, and feeding value for cattle fed high concentrate diets were appraised by statistically compiling results from 605 comparisons from feeding trials published in North American journals and experiment station bulletins since 1974. Metabolizable energy (ME) values for each grain and processing method were calculated by quadratic procedures from DMI and animal performance. Averaged across processing methods, ME values for corn, milo, and wheat grain (3.40, 3.22, and 3.46 Mcal/kg DM) fell within 9% of ME estimates from NRC (1996) for beef cattle. In contrast, ME values for barley and oats grain (3.55 and 3.46 Mcal/kg DM) were 24% and 17% greater than NRC (1996) estimates. Compared with the dry rolled forms, high moisture corn and milo resulted in lower ADG and DMI. Compared with dry rolling, either steam rolling or flaking of corn, milo, and wheat decreased DMI without decreasing ADG and improved feed efficiency by 10, 15, and 10%, respectively. Compared with dry rolled grain, steam flaking increased (P < .05) body weight-adjusted ME of corn and milo grain by 15 and 21%, respectively; body weight-adjusted ME for whole corn was 9% greater (P < .05) than for rolled corn grain. Steam flaking was surprisingly effective (13%) at increasing (P < .05) the body weight-adjusted ME of wheat, but steam flaking failed to increase the ME of barley and oats. Higher moisture content of high-moisture corn decreased dry matter intake without depressing ADG and improved efficiency and increased ME of the grain. Compared with steam flakes of moderate thinness, processing milo or barley to a very thin flake tended to reduce ADG and failed to improve feed efficiency. The ideal roughage source and roughage moisture content for maximum ME and ADG varied with grain processing method. Feeding corn silage rather than alfalfa and wet rather than dry roughage depressed (P < .01) ADG of cattle and reduced (P < .01) body weight-adjusted ME of cattle fed high-moisture corn grain but tended to increase both with steam-flaked corn or wheat.

Analysis of the chronic wound microbiota of 2,963 patients by 16S rDNA pyrosequencing
Randall D. Wolcott, Randall D. Wolcott, John D. Hanson, Eric J. Rees +4 more
2015· Wound Repair and Regeneration413doi:10.1111/wrr.12370

The extent to which microorganisms impair wound healing is an ongoing controversy in the management of chronic wounds. Because the high diversity and extreme variability of the microbiota between individual chronic wounds lead to inconsistent findings in small cohort studies, evaluation of a large number of chronic wounds using identical sequencing and bioinformatics methods is necessary for clinicians to be able to select appropriate empiric therapies. In this study, we utilized 16S rDNA pyrosequencing to analyze the composition of the bacterial communities present in samples obtained from patients with chronic diabetic foot ulcers (N = 910), venous leg ulcers (N = 916), decubitus ulcers (N = 767), and nonhealing surgical wounds (N = 370). The wound samples contained a high proportion of Staphylococcus and Pseudomonas species in 63 and 25% of all wounds, respectively; however, a high prevalence of anaerobic bacteria and bacteria traditionally considered commensalistic was also observed. Our results suggest that neither patient demographics nor wound type influenced the bacterial composition of the chronic wound microbiome. Collectively, these findings indicate that empiric antibiotic selection need not be based on nor altered for wound type. Furthermore, the results provide a much clearer understanding of chronic wound microbiota in general; clinical application of this new knowledge over time may help in its translation to improved wound healing outcomes.

An In Vivo Polymicrobial Biofilm Wound Infection Model to Study Interspecies Interactions
Trevor Dalton, Scot E. Dowd, Randall D. Wolcott, Yan Sun +3 more
2011· PLoS ONE377doi:10.1371/journal.pone.0027317

Chronic wound infections are typically polymicrobial; however, most in vivo studies have focused on monospecies infections. This project was designed to develop an in vivo, polymicrobial, biofilm-related, infected wound model in order to study multispecies biofilm dynamics and in relation to wound chronicity. Multispecies biofilms consisting of both Gram negative and Gram positive strains, as well as aerobes and anaerobes, were grown in vitro and then transplanted onto the wounds of mice. These in vitro-to-in vivo multi-species biofilm transplants generated polymicrobial wound infections, which remained heterogeneous with four bacterial species throughout the experiment. We observed that wounded mice given multispecies biofilm infections displayed a wound healing impairment over mice infected with a single-species of bacteria. In addition, the bacteria in the polymicrobial wound infections displayed increased antimicrobial tolerance in comparison to those in single species infections. These data suggest that synergistic interactions between different bacterial species in wounds may contribute to healing delays and/or antibiotic tolerance.

Soil Moisture and Temperature Effects on Nitrogen Release from Organic Nitrogen Sources
Shinsuke Agehara, D. D. Warncke
2005· Soil Science Society of America Journal373doi:10.2136/sssaj2004.0361

Nitrogen release from organic N sources is controlled by the soil environment. Soil incubation was conducted to evaluate the effects of soil moisture (50, 70, and 90% of water holding capacity) and temperature (15/10, 20/15, and 25/20°C [14/10 h]) on N release from four organic N sources. Differential N release kinetics of the N sources were determined by measuring ammonium‐ and nitrate‐N contents periodically over 12 wk. Net N released, as a percentage of organic N, was greatest in the order: urea (91–96%) &gt; blood meal (BM) (56–61%) &gt; alfalfa pellets (AP) (41–52%) &gt; partially composted chicken manure (CM) (37–45%). Increasing soil moisture increased net N released from AP and CM by 12 and 21%, respectively, but did not significantly affect net N released from urea and BM. Increasing temperature increased net N released from AP, BM, and CM by 25, 10, and 13%, respectively, but did not significantly affect net N released from urea. The results indicate that soil moisture and temperature influence N availability from organic N materials differently depending on source of N. In greenhouse production systems, where irrigation and temperature can be controlled, fertilizer management that considers both source of N and soil environment may improve the effectiveness of organic N materials.