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Interactive Effects of Copper on Alfalfa Growth, Soil Copper, and Soil Bacteria
Get PDFCopper sulfate foot baths are a management practice used by dairy farms in an effort to control hoof infections. As an unintended consequence, agricultural soils experience Cu accumulation when spent foot baths are disposed of in wastewater lagoons that are utilized for irrigation purposes. We investigated the effect of Cu applications (up to 1000 mg/kg) to a Xeric Haplocalcid (Declo series) and a Typic Calciaquoll (Logan series) on alfalfa (Medicago sativa) growth and Cu concentration, soil total and diethylenetriaminepentaacetic acid (DTPA)-extractable Cu, and the soil microbial community diversity using ribosomal intergenic spacer analysis (RISA). Copper application up to 250 mg/kg did not affect alfalfa growth; above 500 mg/kg alfalfa did not grow. The 100 and 250 mg/kg Cu application rates increased alfalfa Cu content grown in Declo soil, while the 250 mg/kg Cu application rate increased alfalfa Cu content when grown in the Logan soil. Regardless of initial application rate, 48 to 80% of the added Cu was still plant-available at the end of the study. Comparing DTPA-extractable Cu to alfalfa Cu concentrations, 63 or 95 mg/kg of DTPA-extractable soil Cu for the Declo and Logan soils, respectively, would be detrimental in terms of cattle dietary Cu intake. For Declo soils, microbial diversity remained relatively stable across all Cu application rates; Logan soils saw a peak in microbial diversity at the 50 mg/kg Cu application rate. Cluster analysis revealed differences in the microbial RISA profiles between the lower and higher Cu application rates. To prevent excessive alfalfa Cu accumulation and negative impacts on the soil microbial community, it is recommended available soil Cu not exceed 63 mg/kg in agroecosystems associated with these soil series
Concentrations of Airborne Endotoxin and Microorganisms at a 10,000 Cow Open-Freestall Dairy
Get PDFConfined animal production systems produce elevated bioaerosol concentrations, which are a potential respiratory health risk to individuals on site and downwind. In this study, airborne endotoxin and microorganisms were collected during the spring, summer, and fall at a large open-freestall dairy in southern Idaho. Compared to the background ambient atmosphere, both endotoxin and culturable heterotrophic bacteria concentrations were up to several-hundred fold greater 50 m downwind from the facility, then decreased to near background concentrations at 200 m. However, downwind fungi concentrations were not elevated above background concentrations. At 50 m downwind, the average inhalable endotoxin concentration ranged from 4.6 to 4243 endotoxin units/cubic meter of air, while bacteria concentrations ranged from 102 to 104 colony forming units (CFU)/cubic meter. Although the bioaerosol concentrations did not follow a seasonal trend, they did significantly correlate with meteorological factors. Increasing temperature was found to be positively correlated with increasing endotoxin, bacteria, and fungi concentrations, while an inverse relationship occurred between the concentration and solar radiation. The airborne concentrations at 50 m were also found to be greatest at night, which can likely be attributed to changes in animal activity and wind speed and reduced exposure of the airborne microorganisms to ultraviolet radiation
Influence of Rhizoctonia-bacterial Root Rot Complex on Storability of Sugarbeet
Get PDFThe Rhizoctonia-bacterial root rot complex can lead to yield loss in the field but may also lead to problems with sucrose loss in storage. Thus, studies were conducted to investigate if placing sugarbeet roots suffering from root rot together with healthy roots could compromise the ability of the healthy roots to retain sucrose. Over a three year period, root samples from three commercial cultivars were compared in storage as a healthy (eight healthy roots) or rotted (eight healthy roots + one rotted root) treatment inside an outdoor storage pile. The experiment was arranged as a split block (healthy in one half of block and rotted in the other) with the whole blocks arranged in a randomized complete block design with four replications. Samples were retrieved from storage in December, January, and February and evaluated for discolored and frozen root area, weight loss, and sucrose reduction and recovery. When comparing the healthy to the rotted treatment over the nine year x sampling date combinations, the Wilcoxon signed-rank test indicated the median change for discoloration (7% increase), frozen area (14% increase), sucrose loss (5% loss), and recoverable sucrose (689 kg/ha less or 8% reduction) were significantly different from zero (P = 0.008, 0.031, 0.007, and 0.008, respectively). These data indicate that the Rhizoctonia-bacterial root rot complex not only leads to yield loss in the field but can also negatively affect neighboring healthy roots in storage leading to additional sucrose losses
High yield corn production can result in high nitrogen use efficiency
Get PDFAlarm is expressed about the environmental impact of the increasing amount of reactive N in the atmosphere and in terrestrial and marine ecosystems around the globe. Much of this increase is attributed to production and use of N fertilizer. Use of fertilizer N is essential to meet growing global demand for agricultural commodities. Management is key to increasing productivity while also increasing N use efficiency and reducing N losses. A team of University of Nebraska-Lincoln scientists, with partial funding from the Nebraska State Legislature, addressed this challenge. They conducted 32 irrigated trials across diverse production conditions of Nebraska from 2002 to 2004 to evaluate corn response to rates of split-applied N. The results were reported in two papers published in the January-February 2011 issue of Agronomy Journal. The results demonstrate the potential to achieve high N use efficiency by corn in high yield situations, compared with typical efficiencies, provided N was applied near the economical optimum N rate. Several factors contributed to high fertilizer N recovery: no fall N application; split application of N; avoiding sites prone to water-logging and leaching to minimize nitrate-N losses; crop management to have a healthy crop with a vigorous root system efficient in both nutrient uptake and conversion of nutrients and carbohydrates to grain; and irrigation management to avoid leaching and denitrification losses and to avoid crop stress
Drinking Water Treatment Residuals: A Reveiw of Recent Uses
Get PDFCoagulants such as alum, [Al2(SO4)3X14H2O], ferric chloride [FeCl3], or ferric sulfate [Fe2(SO4)3] are commonly used to remove particulate and dissolved constituents from water supplies in the production of drinking water. The resulting waste product, called water-treatment residuals (WTR), contains precipitated Al and Fe oxyhydroxides resulting in a strong affinity for anionic species. Recent research has focused on using WTR as cost-effective materials to reduce soluble phosphorus (P) in soils, runoff, and land-applied organic wastes (manures and biosolids). Studies show P adsorption by WTR to be fast and nearly irreversible, suggesting long-term stable immobilization of WTR-bound P. Because excessive WTR application can induce P deficiency in crops, effective application rates and methods remain an area of intense research. Removal of other potential environmental contaminants [ClO4, Se(+IV and +VI), As(+III and +V), Hg] by WTR has been documented, suggesting potential use of WTRs in environmental remediation. While creation of Al plant toxicity and enhanced Al leaching are concerns expressed by researchers, at circumneutral soil pH conditions these effects are minimal. Radioactivity, trace element levels, and enhanced Mn leaching have also been cited as potential problems in WTR usage as a soil supplement. However, these issues can be managed so as not to limit the beneficial use of WTRs in controlling off-site P losses to sensitive water bodies or reducing soil-extractable P concentrations
Infiltration Model for Center Pivot Sprinkler Irrigation
Get PDFThe marked reduction in infiltration rate caused by formation of a soil surface seal due to water droplet impact on bare soil is a well known phenomenon but is rarely considered in infiltration models, especially under center pivot irrigation. The objective of this study was to develop a soil infiltration model for center pivot sprinkler irrigation that incorporates the transient reduction in soil surface seal hydraulic conductivity as affected by soil and sprinkler characteristics. A sealing soil infiltration model was developed using an explicit finite difference solution scheme with a transient soil seal formation model, which is unique from other studies in that it explicitly uses droplet specific power as the driving factor for formation of a soil surface seal. The model was calibrated to a specific soil using published runoff data from a rainfall simulation study with varying droplet kinetic energies and application rates. The model was then applied to center pivot irrigation for five common sprinklers to evaluate the effect sprinkler selection has on infiltration. Due to the high susceptibility of the soil to surface sealing from water drop impact and low satiated hydraulic conductivity, the sprinkler with the largest wetted diameter was predicted to maximize infiltration. The infiltration model predicted an average difference of 3.2 mm between protected and bare soil infiltration for a 25.4 mm application depth. Sprinkler kinetic energy had minimal impact on infiltrated depth because all the sprinklers used in this study caused a surface seal
Effect of Sprinkler Pressure and Spray Plate on Culturable Microorganism Concentrations During Simulated Irrigation of Dairy Wastewater
Get PDFIn this study we conducted simulated spray irrigation events of dairy wastewater to assess the impact of pressure and sprinkler type upon post-sprinkler culturable microorganism concentrations. Dairy wastewater was sampled before and after it was pumped through sprinklers typically used on center pivot irrigation systems. Three different sprinklers types were used at three different operating pressures to give a range of water drop sizes. The microorganisms quantified in this study were total coliforms, Escherichia coli, Clostridium perfringens, heterotrophic bacteria, and coliphage. In most cases the pre- and post-sprinkler concentrations were determined to be statistically similar, suggesting that culturable viability was not affected when wastewater flowed through these sprinklers. When an impact was found to occur, there was usually an increase in the post-sprinkler microorganism concentration. While this increase can be attributed to the disruption of microbial aggregates during the spraying process, there was no apparent relationship with pressure setting or spray plate. Understanding impacts at the sprinkler-level should be considered an integral part of the dispersion modeling process, as it may influence the number of viable microorganisms that become aerosolized during pressurized irrigation events
Airborne Endotoxin from Indoor and Outdoor Environments: Effects of Sample Dilution on the Kinetic Limulus Amebocyte Lysate (LAL) Assay.
Get PDFAirborne endotoxin in occupational environments are a potential respiratory hazard to individuals. In this study, total and inhalable airborne endotoxin samples were collected via filtration from inside animal housing units and downwind from agricultural production sites and a wastewater treatment plant. Filter extracts were then diluted to examine the effect of interfering substances on the kinetic Limulus amebocyte lysate (LAL) assay. In most cases, the overall endotoxin concentration was shown to decrease with increasing dilution up to 1,000-fold, suggesting the presence of enhancing substances in the filter extracts. This dilution dependent effect was most prominent in the inhalable endotoxin samples, while total endotoxin samples displayed little effect. Using a joinpoint regression model, it was determined that a dilution factor of 50 to 100 was generally sufficient to eliminate the presence of enhancing substances. After screening the data for dilution dependent effects, the airborne endotoxin concentrations were determined. The highest endotoxin concentrations, ranging from 2,841 to 49,066 endotoxin units (EU) m-3 of air, were found inside swine farrowing and finishing barns. Airborne endotoxin concentrations were 10- to 1,000-fold lower inside a dairy barn and downwind of other agricultural production sites and a wastewater treatment plant. Examination of dilution dependent effects should be considered essential when utilizing the LAL assay, especially if values are to be used for regulatory purposes
Zeolite Soil Application Method Affects Inorganic Nitrogen, Moisture, and Corn Growth
Get PDFAdoption of new management techniques which improve soil water storage and soil nitrogen plant availability yet limit nitrogen leaching may help improve environmental quality. A benchtop study was conducted to determine the influence of a single urea fertilizer rate (224 kilograms of Nitrogen per hectare) applied with band or fully-mixed zeolite (Clinoptilolite) application rates (up to 90 megagrams per hectare) on ammonium-nitrogen and nitrate-nitrogen concentrations in a Portneuf silt loam. Two additional greenhouse experiments were carried out to test the soil moisture status and corn growth in a Wolverine sand. Mixing urea fertilizer into silt loam soil resulted in greater urea mineralization, but the mixed zeolite was more effective at adsorbing and protecting ammonium-nitrogen against nitrification as compared to band application of fertilizer + zeolite. Increasing the rate of mixed zeolite into sandy soil increased the soil moisture content, and mixed zeolite soils contained 1.3% more soil moisture as compared to band zeolite applications. Following six weeks of corn growth in amended sandy soil, zeolite application at 22 megagrams per hectare appeared to increase corn weight compared to controls. However, increasing zeolite rate up to 90 megagrams per hectare caused a decrease in corn weight, likely due to the elevated zeolite Na content (3%). Fully mixing zeolite into soil reduces the rate of nitrification likely due to ammonium adsorption in the zeolite mineral lattice. Thus, mixing zeolite into soil may reduce the leaching of inorganic N. Mixing may also improve the soil water status, although initial leaching of zeolite-borne Na may be necessary before growing crops
Beet curly top resistance of USDA-ARS National Plant Germplasm System Plant Introductions, 2009.
Get PDFThirty wild beet (Beta vulgaris subsp. maritima (L.) Arcang) accessions from the Beta Collection of the USDA-ARS National Plant Germplasm System were screened for resistance to Beet severe curly top virus (BSCTV) in 2009. The curly top evaluation was conducted at the USDA-ARS North Farm in Kimberly, ID which had been in beans in 2008. The field was plowed in the fall, fertilized (75 lb N/A and 75 lb P2O5/A) on 22 Apr 09, sprayed with Ethotron (2 pt/A), and roller harrowed. The germplasm was planted (density of about 143,000 seeds/A) on 18 May. The plots were two rows 10 ft long with 22-in row spacing and arranged in a randomized complete block design with three replications. A resistant breeding line from Betaseed, Inc., G6040, was included as a resistant check. The fields were sprinkler irrigated and hand weeded as necessary. Plant populations were thinned to about 47,500 plants/A on 19 Jun. Plants were inoculated at the four to six leaf growth stage on 23 Jun with six viruliferous beet leafhoppers per plant. The beet leafhoppers were moved twice a day (right after sunrise and just before sunset) for one week by dragging a tarp through the field. The plants were sprayed with Lorsban 4E (1.5 pints/A) on 7 Jul to kill the beet leafhoppers. The plots were rated for foliar symptom development using a scale of 0-9 where 0 = healthy and 9 = dead (Mumford, D.L. 1974. Procedure for inducing curly top epidemics in field plots. J. Am. Soc. Sugar Beet Technol. 18:20-23), with disease index (DI) treated as a continuous variable. Data were analyzed using the general linear models procedure (Proc GLM-SAS), and least significant difference was used for mean comparisons.
Disease development was uniform and severe. Other disease problems were not evident in the plot area. The PIs were a combination of annual and biennial plant types. The resistant check was significantly more resistant than any of the tested germplasms. None of the lines tested appeared to be resistant to BSCTV. The two best germplasm were Beta vulgaris subspecies maritima lines, both of which contained biennial plants. However their scores were much higher than the resistant check and do not seem to contain resistance to BSCTV