bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimal Pricing of Seasonal Products in the Presence of Forward-Looking Consumers
Authors: Aviv Yossi , Pazgal Amit
Published: January 2008

We study the optimal pricing of a finite quantity of a fashion-like seasonal good in the presence of forward-looking (strategic) customers. We distinguish between two classes of pricing strategies: contingent and announced fixed-discount. In both cases, the seller acts as a Stackelberg leader announcing his pricing strategy, while consumers act as followers taking the seller's strategy as given and determining their purchasing behavior. In each case, we identify a subgame-perfect Nash equilibrium and show that given the seller's strategy, the equilibrium in the consumer subgame is unique and consists of symmetric threshold purchasing policies. For both cases, we develop a benchmark model in which customers are nonstrategic (myopic). We conduct a comprehensive numerical study to explore the impact of strategic consumer behavior on pricing policies and expected revenue performance. We show that strategic customer behavior suppresses the benefits of price segmentation, particularly under medium-to-high values of heterogeneity and modest rates of decline in valuations. However, when the level of consumer heterogeneity is small, the rate of decline is medium-to-high, and the seller can optimally choose the time of discount in advance, segmentation can be used quite effectively even with strategic consumers. We find that the seller cannot avoid the adverse impact of strategic consumer behavior even under low levels of initial inventory. We argue that while the seller expects customers to be more concerned about product availability at discount time, he cannot use high-price “betting” strategies as he would in the case of low inventory and myopic customers. Under certain qualifications, announced fixed-discount strategies perform essentially the same as contingent pricing policies in the case of myopic consumers. However, under strategic consumer behavior, announced pricing policies can be advantageous to the seller, compared to contingent pricing schemes. Interestingly, those cases that announced discount strategies offer a significant advantage compared to contingent pricing policies. They appear to offer only a minimal advantage in comparison to fixed-pricing policies. Finally, when the seller incorrectly assumes that strategic customers are myopic in their purchasing decisions, it can be quite costly, reaching potential revenue losses of about 20%.
Competitive Customization
Authors: Mendelson Haim , Parlaktürk Ali K.
Published: January 2008

We consider a duopoly market with heterogeneous customer tastes. The firms play a two-stage game. First, each firm chooses whether to invest in mass customization, which would enable it to offer customized products that increasingly match each customer's ideal product as the chosen customization level increases. A firm that chooses not to invest in mass customization serves a standard product. Second, the firms competitively price their product lines. We characterize each firm's investment in mass customization and study its dependence on competitive position, as determined by its cost efficiency and perceived quality vis-à-vis its competitor. We find that the value of mass customization critically depends on the firm's competitive position. It may not be desirable even at zero cost due to its negative effect on price competition. A firm with an overall cost and quality disadvantage never unilaterally adopts mass customization. We show that allowing firms to set different prices for each product configuration leads to a broader adoption of mass customization compared to when they are restricted to uniform prices. However, a firm's chosen customization level may be higher with uniform prices. Our analysis also helps a customizing firm determine whether to target its process improvement efforts for a lower cost or a higher customization level.
Newsvendors Under Simultaneous Price and Inventory Competition
Authors: Zhao Xuan , Atkins Derek R.
Published: January 2008

This paper extends the theory of N competitive newsvendors to the case where competition occurs simultaneously in price and inventory. The basic research questions are whether the Nash equilibrium exists in this game, whether it is unique, and how the resulting inventories and prices are affected by competition. Using a novel method, we show the quasiconcavity of the competitive newsvendor's problem and establish the existence of the pure-strategy Nash equilibrium. Through a contraction mapping approach, we develop sufficient conditions for the Nash equilibrium to be unique. We then analyze the properties of the equilibrium and compare it with the optimal solution for the (noncompeting) price-sensitive newsvendor. We prove that at a symmetric equilibrium, retail prices and safety stocks strictly increase with the proportion of a newsvendor's unsatisfied customers that switch to a competitor, but strictly decrease with the intensity of price competition. Total inventories, on the other hand, increase with the intensity of price competition. Furthermore, the competitive equilibrium never has lower safety stocks and higher retail prices (a situation that definitely hurts the customers) than the solution for noncompetitive newsvendors.
Pricing Promotional Products Under Upselling
Authors: Aydin Goker , Ziya Serhan
Published: January 2008

Upselling is offering an additional product to a customer who just made a purchase. Most catalogers and online sellers, in addition to some traditional retailers, use upselling often to clear inventories of slow-moving items. We investigate the pricing and discounting questions for such an item, which we call the promotional product. In our model, an arriving customer may purchase this promotional product or one of the other products that the firm sells. If the customer purchases one of the other products, the promotional product is offered to the customer, possibly with a discount. While deciding whether to offer a discount and, if so, how big a discount to offer, the firm uses the information that the customer has just bought a certain product with a certain price. We investigate how discounting decisions depend on the inventory levels, time, type of pricing policy in use, and the relationship between the customers' reservation prices for the promotional product and the other products (negatively or positively correlated). In particular, we find that if the firm sets prices and discounts dynamically and the customers' reservation prices for the promotional product are negatively correlated with their reservation prices for the product they purchased, then customers are always offered a discount regardless of the inventory levels and time. On the other hand, if the customers' reservation prices for the promotional product are positively correlated with their reservation prices for the product they purchased, then the customer may or may not be offered a discount, depending on the inventory levels and time. Our numerical study shows that the benefit to the firm from using customer purchase information is high when the firm uses a static price, but chooses discounts dynamically. We also find that although dynamic discounting decisions bring modest improvements, setting the price dynamically seems to have a more significant effect on the firm's profits.
Inventory Service-Level Agreements as Coordination Mechanisms: The Effect of Review Periods
Authors: Katok Elena , Thomas Douglas , Davis Andrew
Published: January 2008

Asupplier stocking goods for delivery to a retailer may face a (finite-horizon) service-level agreement (SLA). In this context, the SLA is a commitment by a supplier to achieve a minimum fill rate over a specified time horizon. This kind of SLA is an important, but understudied coordination mechanism. We focus on the impact of two contract parameters: the length of the review period and the magnitude of the bonus for meeting or exceeding the service-level target. For a supplier following a base stock (order-up-to) inventory policy, increasing the bonus increases optimal supplier stocking levels, whereas lengthening the review period may increase or decrease optimal stocking levels. We investigate these mechanisms in a controlled laboratory setting and find that longer review periods are generally more effective than shorter review periods in inducing higher stocking levels. As in several earlier laboratory studies, the explanation lies in the improved feedback reliability that longer review periods provide. The primary managerial implication of our findings is that, in practice, longer review periods may be more effective than shorter ones at inducing service improvements.
A Stochastic Inventory Model with Trade Credit
Authors: Gupta Diwakar , Wang Lei
Published: January 2008

Suppliers routinely sell goods to retailers on credit. Common credit terms are tantamount to a schedule of declining discounts (escalating penalties) that depend on how long the retailer takes to pay off the supplier's loan. However, issues such as which stocking policies are optimal in the presence of supplier-provided credit have been investigated only when demand is assumed deterministic. Nearly all stochastic inventory models assume either time-invariant finance charges or charges that may vary with time but not with the age of the credit. In this article we present a discrete time model of the retailer's operations with random demand, which is used to prove that the structure of the optimal policy is not affected by credit terms, although the value of the optimal policy parameter is. This is followed by a continuous time model, which leads to an algorithm for finding the optimal stock level. We also model the supplier's problem and calculate the optimal credit parameters in numerical experiments.
A Pooling Analysis of Two Simultaneous Online Auctions
Authors: Beil Damian R. , Wein Lawrence M.
Published: January 2008

Motivated by the ease with which online customers can bid simultaneously in multiple auctions, we analyze a system with two competing auctioneers and three types of bidders: those dedicated to either of the two auctions and those that participate simultaneously in both auctions. Bidding behavior is specified and proven to induce a Bayesian Nash equilibrium, and a closed-form expression for the expected revenue of each auctioneer is derived. For auctioneers selling a single item, partial pooling—i.e., the presence of some cross-auction bidders—is beneficial to both auctioneers as long as neither one dominates the market (e.g., possesses more than 60%–65% of the market share). For multi-item auctions, pooling is mutually beneficial only if both auctioneers have nearly identical ratios of bidders per items for sale; otherwise, only the auctioneer with the smaller ratio benefits from pooling. Pooling's impact on revenue decreases with the number of bidders, suggesting that popular auction sites need not be overly concerned with mitigating bidding across auctions.
Sensitivity of Optimal Capacity to Customer Impatience in an Unobservable M/M/S Queue (Why You Shouldn't Shout at the DMV)
Authors: Armony Mor , Plambeck Erica , Seshadri Sridhar
Published: January 2008

This paper employs sample path arguments to derive the following convexity properties and comparative statics for an M/M/S queue with impatient customers. If the rate at which customers balk and renege is an increasing, concave function of the number of customers in the system (head count), then the head-count process and the expected rate of lost sales are decreasing and convex in the capacity (service rate or number of servers). This result applies when customers cannot observe the head count, so that the balking probability is zero and the reneging rate increases linearly with the head count. Then the optimal capacity increases with the customer arrival rate but is not monotonic in the reneging rate per customer. When capacity is expensive or the reneging rate is high, the optimal capacity decreases with any further increase in the reneging rate. Therefore, managers must understand customers' impatience to avoid building too much capacity, but customers have an incentive to conceal their impatience, to avoid a degradation in service quality. If the system manager can prevent customers from reneging during service (by requiring advance payment or training employees to establish rapport with customers), the system's convexity properties are qualitatively different, but its comparative statics remain the same. Most important, the prevention of reneging during service can substantially reduce the total expected cost of lost sales and capacity. It increases the optimal capacity (service rate or number of servers) when capacity is expensive and reduces the optimal capacity when capacity is cheap.
Pointwise Stationary Fluid Models for Stochastic Processing Networks
Authors: Bassamboo Achal , Harrison J. Michael , Zeevi Assaf
Published: January 2008

Generalizing earlier work on staffing and routing in telephone call centers, we consider a processing network model with large server pools and doubly stochastic input flows. In this model the processing of a job may involve several distinct operations. Alternative processing modes are also allowed. Given a finite planning horizon, attention is focused on the two-level problem of capacity choice and dynamic system control. A pointwise stationary fluid model (PSFM) is used to approximate system dynamics, which allows development of practical policies with a manageable computational burden. Earlier work in more restrictive settings suggests that our method is asymptotically optimal in a parameter regime of practical interest, but this paper contains no formal limit theory. Rather, it develops a PSFM calculus that is broadly accessible, with an emphasis on modeling and practical computation.
Note—Optimal Component Acquisition for a Single-Product, Single-Demand Assemble-to-Order Problem with Expediting
Authors: Fu Ke , Hsu Vernon N. , Lee Chung-Yee
Published: January 2008

We consider a component acquisition problem for a contract manufacturer who faces a one-time stochastic demand for a single product consisting of a number of components. Components can be ordered early at normal prices before the demand is revealed, or they can be replenished later at higher prices due to expediting. In addition, the customer pays a price for the final product that is nonincreasing in the delivery lead time to discourage late delivery. We propose a cost-minimization model and develop an efficient polynomial time algorithm to solve the problem.
Optimal Policy for a Periodic-Review Inventory System Under a Supply Capacity Contract
Authors: Chao Xiuli , Zipkin Paul H.
Published: January 2008

Transportation and production contracts often specify the frequency and volume reserved by the supplier for a particular customer's deliveries. This practice motivated Henig et al. (Henig, M., Y. Gerchak, R. Ernst, D. Pyke. 1997. An inventory model embedded in designing a supply contract. Management Sci. 43 184–189) to study a periodic-review inventory-control model where ordering cost is zero if the order quantity does not exceed a given contract volume and is linear in the excess quantity otherwise. This paper addresses the same problem but with a fixed cost if the order quantity is above the contract volume. The fixed cost may represent the cost of disruption for the supplier (finding more trucks, arranging extra processing capacity, persuading other customers to wait, etc.) as well as additional administrative costs. Also, suppliers may impose such costs simply to induce desired behavior by buyers. This order-cost function is neither convex nor concave. The classical inventory models with fixed costs are special cases with contract volume zero. We partially characterize the optimal policy for this system and develop a simple, effective heuristic policy. We also apply the model to a production-control problem in which an incentive is provided for not ordering over a certain quota.
Hans Ulrich Gumbrecht, Diesseits der Hermeneutik. Die Produktion von Präsenz. 2004
Authors: Mersch Dieter
Published: January 2008

„Statt einer Hermeneutik brauchen wir eine Erotik der Kunst“, notierte bereits 1964 Susan Sontag in ihrem Essay Against Interpretation. Seit Jahren ist auch Hans Ulrich Gumbrecht an einem Ausbruch aus dem hermeneutischen Gefängnis interessiert, sucht er ein „Anderes“ des hermeneutischen Verfahrens zu denken und ein „Nicht-Hermeneutisches“ einzuüben. „Heute zeichnet sich eine Konvergenz von Reflexionen im Nicht-Hermeneutischen ab“, schrieb Gumbrecht schon vor mehr als zehn Jahren; doch konstatierte er zugleich, daß sich die „Umrisse des Feldes von nicht-hermeneutischen Theorien und Forschungspraktiken“ vorerst nur unbestimmt und unscharf abzeichneten. Mit Diesseits der Hermeneutik legt Gumbrecht nun eine Studie vor, die seit dem zusammen mit K. Ludwig Pfeiffer herausgegebenen Sammelband Materialität der Kommunikation die Ergebnisse eines jahrelangen Forschungsprozesses über das bündelt, was sich dem Sinn entzieht. Die Schlüsselkategorien lauten „Präsenz“ und „Präsentifikation“, „Ereignis“ und „Epiphanie“, „Deixis“ und „Erscheinen“. Es gibt ein „Verlangen“, ein „Begehren nach Präsenz“ (S. 37, 126) heißt es mit Jean-Luc Nancy in der aus unterschiedlichen Beiträgen gebauten Studie, die immer wieder das „Vergessen der Nähe“ (S. 163) und den „Verlust der Präsenzdimensionen in unserer heutigen Kultur“ (S. 165) beklagt, „denn wir leben in einer Umwelt, die es uns gar nicht gestattet, länger als für Momente der Präsenz innezuhalten“ (S. 164). Fehlten unserer „dermaßen mit Sinn gesättigten Welt […] Phänomene und Eindrücke von Präsenz“ (S. 126), so setzt Gumbrecht auf die „Produktion von Präsenz“ – mit dem erklärten Ziel, den Regimen des Sinns und dem „Zeitalter des Zeichens“ ein „Ende zu setzen“ (S. 70f.).
A single injection of double-stranded adeno-associated viral vector expressing GH normalizes growth in GH-deficient mice
Authors: Sagazio Alessia , Xiao Xiao , Wang Zhong , Martari Marco , Salvatori Roberto
Published: January 2008

GH is secreted by the somatotropic cells of the pituitary gland, and its deficiency (GHD) impairs longitudinal growth. Due to its short half-life, GH therapy needs administration of GH injections daily. Adeno-associated viral vectors (AAV) can deliver gene therapy to animals with possible future applications in humans. The new generation of double-stranded AAV vectors (dsAAV) provides widespread, strong, and stable transgene expression without toxicity and immune response. To determine whether such a new system could be used to deliver GH to a mouse model of isolated GHD due to ablation of the GHRH knock-out gene (GHRHKO), we have created AAV viral particles containing mouse GH cDNA driven by a cytomegalovirus promoter (dsAAV8-CMV-GH), and tested them in male GHRHKO mice. GHRHKO animals received either a single (low dose) or two (high dose) i.p. injections of dsAAV8-CMV-GH (1×1011 particles) at the 10th and 11th days of age, or a placebo injection, and were followed up to the 6th or 24th week of life. A single dsAAV8-GH injection caused body length and weight normalization. At week 6, serum GH was higher in mice receiving both virus doses compared with controls, while it was normal at week 24. Serum IGF-1 increased in both virus-treated groups, and it was normal at 24 weeks. GH mRNA expression was detected in liver, skeletal, and heart muscle of virus-injected animals. These data show that normalization of longitudinal growth can be reached in GHD mice using a single injection of a double-stranded adeno-associated virus expressing GH.
Differential long-term dietary regulation of adipokines, ghrelin, or corticosterone: impact on adiposity
Authors: Beck Bernard , Richy Sébastien
Published: January 2008

In the present experiment, we examined in Long–Evans rats the long-term effects of diets that differed in the energy provided by proteins (P) and fats (F) but provided a constant level of energy from carbohydrates (55%) on various hormones regulating feeding and metabolism. Sixty adult rats were fed for 2 months either a high-fat (protein-to-fat, PF 5/40), a control (PF 15/30), low-fat (PF 30/15), or high-protein (PF 40/5) diet ad libitum. Both the PF 30/15 and the PF 40/5 rats ate significantly less than their PF 5/40 and PF 15/30 counterparts throughout the experiment (P<0.001). PF 40/5 rats weighed less than PF 15/30 rats (PL=0.04). PF 40/5 and PF 30/15 rats had smaller epididymal and perirenal adipose tissue depots than PF 5/40 and PF 15/30 rats (P<0.05 or less). Adiponectin (+25–47%) and leptin levels in the PF 5/40 rats were higher than in the three other groups (P<0.0025 or less). Ghrelin concentration in the PF 30/15 group was also higher than in the three other groups (P<0.001 versus PF 5/40; P<0.05 versus PF 15/30 and PF 40/5). Corticosterone level was 2- to 2.5-fold higher in PF 40/5 rats than in the three other groups (P<0.01 or less). Immunoreactive insulin was not different between the four groups. Our current findings thus show that increases in the protein content resulted in a greater degree of leanness, but at sufficiently high levels, also activated the hypothalamo–pituitary axis. Ghrelin appeared to be down-regulated by increases in fat content and no obvious signs of insulin resistance were observed in any of the rats under study.
Developing Risk Models of Cryptosporidium Transport in Soils from Vegetated, Tilted Soilbox Experiments
Authors: Harter Thomas , Atwill Edward R. , Hou Lingling , Karle Betsy M. , Tate Kenneth W.
Published: January 2008

Transport of Cryptosporidium parvum through macroporous soils is poorly understood yet critical for assessing the risk of groundwater contamination. We developed a conceptual model of the physics of flow and transport in packed, tilted, and vegetated soilboxes during and immediately after a simulated rainfall event and applied it to 54 experiments implemented with different soils, slopes, and rainfall rates. Using a parsimonious inverse modeling procedure, we show that a significant amount of subsurface outflow from the soilboxes is due to macropore flow. The effective hydraulic properties of the macropore space were obtained by calibration of a simple two‐domain flow and transport model that accounts for coupled flow in the matrix and in the macropores of the soils. Using linear mixed‐effects analysis, macropore hydraulic properties and oocyst attenuation were shown to be associated with soil bulk density and rainfall rate. Macropore flow was shown to be responsible for bromide and C. parvum transport through the soil into the underlying pore space observed during the 4‐h experiments. We confirmed this finding by conducting a pair of saturated soil column studies under homogeneously repacked conditions with no macropores in which no C. parvum transport was observed in the effluent. The linear mixed‐effects and logistic regression models developed from the soilbox experiments provide a basis for estimating macropore hydraulic properties and the risk of C. parvum transport through shallow soils from bulk density, precipitation, and total shallow subsurface flow rate. The risk assessment is consistent with the reported occurrence of oocysts in springs or groundwater from fractured or karstic rocks protected only by shallow overlying soils.
Runoff and Leachate Losses of Phosphorus in a Sandy Spodosol Amended with Biosolids
Authors: Alleoni Luis R.F. , Brinton Scott R. , O'Connor George A.
Published: January 2008

Florida Spodosols are sandy, inherently low in Fe‐ and Al‐based minerals, and sorb phosphorus (P) poorly. We evaluated runoff and leachate P losses from a typical Florida Spodosol amended with biosolids and triple superphosphate (TSP). Phosphorus losses were evaluated with traditional indoor rainfall simulations but used a double‐deck box arrangement that allowed leaching and runoff to be determined simultaneously. Biosolids (Lakeland, OCUD, Milorganite, and Disney) represented contrasting values of total P, percent water‐extractable P (PWEP), and percentage of solids. All P sources were surface applied at 224 kg P ha−1, representing a soil P rate typical of N‐based biosolids application. All biosolids‐P sources lost less P than TSP, and leachate‐P losses generally dominated. For Lakeland‐amended soil, bioavailable P (BAP) was mainly lost by runoff (81% of total BAP losses). This behavior was due to surface sealing and drying after application of the slurry (31 g kg−1 solids) material. For all other P sources, BAP losses in leachate were much greater than in runoff, representing 94% of total BAP losses for TSP, 80% for Milorganite, 72% for Disney, and 69% for OCUD treatments. Phosphorus leaching can be extreme and represents a great concern in many coarse‐textured Florida Spodosols and other coastal plain soils with low P‐sorption capacities. The PWEP values of P sources were significantly correlated with total P and BAP losses in runoff and leachate. The PWEP of a source can serve as a good indicator of potential P loss when amended to sandy soils with low P‐retention capacities.
Soil Carbon Dioxide Emission and Carbon Content as Affected by Irrigation, Tillage, Cropping System, and Nitrogen Fertilization
Authors: Sainju Upendra M. , Jabro Jalal D. , Stevens William B.
Published: January 2008

Management practices can influence soil CO2 emission and C content in cropland, which can effect global warming. We examined the effects of combinations of irrigation, tillage, cropping systems, and N fertilization on soil CO2 flux, temperature, water, and C content at the 0‐ to 20‐cm depth from May to November 2005 at two sites in the northern Great Plains. Treatments were two irrigation systems (irrigated vs. non‐irrigated) and six management practices that contained tilled and no‐tilled malt barley (Hordeum vulgaris L.) with 0 to 134 kg N ha−1, no‐tilled pea (Pisum sativum L.), and a conservation reserve program (CRP) planting applied in Lihen sandy loam (sandy, mixed, frigid, Entic Haplustolls) in western North Dakota. In eastern Montana, treatments were no‐tilled malt barley with 78 kg N ha−1, no‐tilled rye (Secale cereale L.), no‐tilled Austrian winter pea, no‐tilled fallow, and tilled fallow applied in dryland Williams loam (fine‐loamy, mixed Typic Argiborolls). Irrigation increased CO2 flux by 13% compared with non‐irrigation by increasing soil water content in North Dakota. Tillage increased CO2 flux by 62 to 118% compared with no‐tillage at both places. The flux was 1.5‐ to 2.5‐fold greater with tilled than with non‐tilled treatments following heavy rain or irrigation in North Dakota and 1.5‐ to 2.0‐fold greater with crops than with fallow following substantial rain in Montana. Nitrogen fertilization increased CO2 flux by 14% compared with no N fertilization in North Dakota and cropping increased the flux by 79% compared with fallow in no‐till and 0 kg N ha−1 in Montana. The CO2 flux in undisturbed CRP was similar to that in no‐tilled crops. Although soil C content was not altered, management practices influenced CO2 flux within a short period due to changes in soil temperature, water, and nutrient contents. Regardless of irrigation, CO2 flux can be reduced from croplands to a level similar to that in CRP planting using no‐tilled crops with or without N fertilization compared with other management practices.
Phosphorus Concentrations in Soil and Subsurface Water: A Field Study among Cropland and Riparian Buffers
Authors: Young Eric O. , Briggs Russell D.
Published: January 2008

Riparian buffers can be effective at removing phosphorus (P) in overland flow, but their influence on subsurface P loading is not well known. Phosphorus concentrations in the soil, soil solution, and shallow ground water of 16 paired cropland‐buffer plots were characterized during 2004 and 2005. The sites were located at two private dairy farms in Central New York on silt and gravelly silt loams (Aeric Endoaqualfs, Fluvaquentic Endoaquepts, Fluvaquentic Eutrudepts, Glossaquic Hapludalfs, and Glossic Hapludalfs). It was hypothesized that P availability (sodium acetate extractable‐P) and soil‐landscape variability would affect P release to the soil solution and shallow ground water. Results showed that P availability tended to be greater in crop fields relative to paired buffer plots. Soil P was a good indicator of soil solution dissolved (<0.45 μm) molybdate‐reactive P (DRP) concentrations among plots, but was not independently effective at predicting ground water DRP concentrations. Mean ground water DRP in corn fields ranged from ≤20 to 80 μg L−1, with lower concentrations in hay and buffer plots. More imperfectly drained crop fields and buffers tended to have greater average DRP, particulate (≥0.45 μm) reactive P (PRP), and dissolved unreactive P (DUP) concentrations in ground water. Soil organic matter and 50‐cm depth soil solution DRP in buffers jointly explained 75% of the average buffer ground water DRP variability. Results suggest that buffers were relatively effective at reducing soil solution and shallow ground water DRP concentrations, but their impact on particulate and organic P in ground water was less clear.
A Whole‐Farm Strategy to Reduce Environmental Impacts of Nitrogen
Authors: Sonneveld M. P. W. , Schröder J. J. , de Vos J. A. , Monteny G. J. , Mosquera J. , Hol J. M. G. , Lantinga E. A. , Verhoeven F. P. M. , Bouma J.
Published: January 2008

Dutch regulations for ammonia emission require farmers to inject slurry into the soil (shallow) or to apply it in narrow bands at the surface. For one commercial dairy farm in the Netherlands it was hypothesized that its alternative farming strategy, including low‐protein feeding and surface spreading, could be an equally effective tool for ammonia emission abatement. The overall objective of the research was to investigate how management at this farm is related to nitrogen (N) losses to the environment, including groundwater and surface water. Gaseous emission of ammonia and greenhouse gasses from the naturally ventilated stables were 8.1 and 3.1 kg yr−1 AU−1 on average using the internal tracer (SF6)‐ratio method. Measurements on volatilization of ammonia from slurry application to the field using an integrated horizontal flux method and the micrometeorological mass balance method yielded relatively low values of ammonia emissions per ha (3.5–10.9 kg NH3–N ha−1). The mean nitrate concentration in the upper ground water was 6.7 mg L−1 for 2004 and 3.0 mg L−1 for 2005, and the half‐year summer means of N in surface water were 2.3 mg N L−1 and 3.4 mg N L−1 for 2004 and 2005, respectively. Using a nutrient budget model for this farm, partly based on these findings, it was found that the calculated ammonia loss per ton milk (range 5.3–7.5 kg N Mg−1) is comparable with the estimated ammonia loss of a conventional farm that applies animal slurry using prescribed technologies.
Bioremediation of Atrazine‐Contaminated Soil by Forage Grasses: Transformation, Uptake, and Detoxification
Authors: Lin C.H. , Lerch R.N. , Garrett H.E. , George M.F.
Published: January 2008

A sound multi‐species vegetation buffer design should incorporate the species that facilitate rapid degradation and sequestration of deposited herbicides in the buffer. A field lysimeter study with six different ground covers (bare ground, orchardgrass, tall fescue, timothy, smooth bromegrass, and switchgrass) was established to assess the bioremediation capacity of five forage species to enhance atrazine (ATR) dissipation in the environment via plant uptake and degradation and detoxification in the rhizosphere. Results suggested that the majority of the applied ATR remained in the soil and only a relatively small fraction of herbicide leached to leachates (<15%) or was taken up by plants (<4%). Biological degradation or chemical hydroxylation of soil ATR was enhanced by 20 to 45% in forage treatment compared with the control. Of the ATR residues remaining in soil, switchgrass degraded more than 80% to less toxic metabolites, with 47% of these residues converted to the less mobile hydroxylated metabolites 25 d after application. The strong correlation between the degradation of N‐dealkylated ATR metabolites and the increased microbial biomass carbon in forage treatments suggested that enhanced biological degradation in the rhizosphere was facilitated by the forages. Hydroxylated ATR degradation products were the predominant ATR metabolites in the tissues of switchgrass and tall fescue. In contrast, the N‐dealkylated metabolites were the major degradation products found in the other cool‐season species. The difference in metabolite patterns between the warm‐ and cool‐season species demonstrated their contrasting detoxification mechanisms, which also related to their tolerance to ATR exposure. Based on this study, switchgrass is recommended for use in riparian buffers designed to reduce ATR toxicity and mobility due to its high tolerance and strong degradation capacity.
Equilibrium Sampling Used to Monitor Malodors in a Swine Waste Lagoon
Authors: Loughrin John H. , Lovanh Nanh , Mahmood Rezaul
Published: January 2008

The concentrations of malodorous compounds in a 0.4‐ha anaerobic lagoon that received waste from approximately 2000 sows were monitored during the late summer to late fall of 2006 to gain insight into the factors influencing their concentrations. Selected malodorous compounds were measured by the use of equilibrium samplers consisting of submersible stir plates and stir bar sorbtive sampling with polydimethylsiloxane‐coated magnetic stir bars. During the same period, air and water temperatures, suspended solids, total organic carbon and nitrogen content, and wastewater pH were recorded. Concentrations of malodorous compounds were higher at the surface of the lagoon than at the middle or bottom of the lagoon. Skatole concentration, for instance, averaged 54, 24, and 38 μg L−1near the surface, in the middle, and at the lowest sampling depths, respectively. While the lagoon was being pumped down during field application of wastewater, concentrations of malodorous compounds fluctuated widely, increased 16‐fold as compared with the sampling period before pumping, and continued to increase as fall progressed and temperatures cooled. Suspended solids, volatile suspended solids, and total organic carbon increased near the bottom of the lagoon during this same period. The increases in the concentrations of malodorous compounds in the wastewater during the fall could have been due to a combination of several factors. These factors include reduced degradation by lagoon bacteria, less wind stripping of volatile compounds from the lagoon surface due to lowering of the lagoon surface after crop application, and/or reduced evaporation of malodorous compounds due to falling temperatures.
Water Quality Effects of Clearcut Harvesting and Forest Fertilization with Best Management Practices
Authors: McBroom Matthew W. , Beasley R. Scott , Chang Mingteh , Ice George G.
Published: January 2008

Nine small (2.5 ha) and four large (70–135 ha) watersheds were instrumented in 1999 to evaluate the effects of silvicultural practices with application of best management practices (BMPs) on stream water quality in East Texas, USA. Two management regimes were implemented in 2002: (i) conventional, with clearcutting, herbicide site preparation, and BMPs and (ii) intensive, which added subsoiling, aerial broadcast fertilization, and an additional herbicide application. Watershed effects were compared with results from a study on the same small watersheds in 1981, in which two combinations of harvesting and mechanical site preparation without BMPs or fertilization were evaluated. Clearcutting with conventional site preparation resulted in increased nitrogen losses on the small watersheds by about 1 additional kg ha−1 each of total Kjeldahl nitrogen (TKN) and nitrate‐nitrogen (NO3–N) in 2003. First‐year losses were not significantly increased on the large watershed with a conventional site preparation with BMPs. Fertilization resulted in increased runoff losses in 2003 on the intensive small watersheds by an additional 0.77, 2.33, and 0.36 kg ha−1 for NO3–N, TKN, and total phosphorus, respectively. Total loss rates of ammonia nitrogen (NH4–N) and NO3–N were low overall and accounted for only ∼7% of the applied N. Mean loss rates from treated watersheds were much lower than rainfall inputs of about 5 kg ha−1 TKN and NO3–N in 2003. Aerial fertilization of the 5‐yr‐old stand on another large watershed did not increase nutrient losses. Intensive silvicultural practices with BMPs did not significantly impair surface water quality with N and P.
Bioassays with Unicellular Algae: Deviations from Exponential Growth and Its Implications for Toxicity Test Results
Authors: Altenburger Rolf , Schmitt‐Jansen Mechthild , Riedl Janet
Published: January 2008

Growth assays with unicellular green algae are an established tool in ecotoxicological effect assessment for chemicals and environmental samples. From an ecological perspective it seems appropriate to use the growth rate as a process variable rather than a measure of biomass gain for calculating inhibitory effects of contaminants. The notion of simple exponential growth for the description of the population increase in undisturbed suspension cultures of unicellular green algae, however, seems to be an oversimplification. Experimental findings describe the increase in biomass, cell number, the development of cell volume distributions of populations, and the relationship between cell size and chlorophyll content for individual cells over one generation at a time resolution of 2‐h intervals. It was observed that algal populations of Desmodesmus subspicatus show a time pattern of cell size growth; the average cell volume increases about sixfold, without corresponding increase in population size. This is followed by a distinct cell division phase with little gain in biomass. This synchronous growth behavior despite continuous illumination may be explained by the multiple fission characteristic of unicellular green algae which is an adaptation to cyclic light–dark changes in the environment. It might be controlled by an independent cell cycle clock. For routine regulatory testing fluorescence‐based measurements rather than cell counting minimizes the confounding effect on toxicity determination. For investigations of time‐dependent effects, e.g., by pulsed exposure, an alternative mechanistically based growth function for unicellular algae is proposed that accommodates for the observed growth pattern.
Hydro‐geochemical Aspects of Mediterranean Temporary Ponds in Western Crete
Authors: Stamati Fotini , Nikolaidis Nikolaos , Dimitriou Elias , Koussouris Theodore
Published: January 2008

The hydrologic and geochemical conditions that prevail in Mediterranean temporary ponds (MTPs), create a unique environment for many rare and endangered species. Mediterranean temporary ponds are habitats of high ecological value, which are vulnerable to imminent climatic changes, as well as to human activities. This article examines the hydrology and the nitrogen and phosphorous geochemical cycles of four MTPs in Crete. Field and laboratory studies provided the necessary information for the development of a conceptual understanding of the hydrologic and biogeochemical processes that affect the fate of nitrogen and phosphorous in these MTPs. Their hydrology was driven by deposition, infiltration, and evaporation. The hydroperiod of the ponds varied between 40 and 160 d. Mineralization and nutrient release capacity experiments illustrated the significant role that MTP sediments played in enhancing the geochemistry of the aqueous phase. Such ecosystem functions (i.e., mineralization, nutrient release) exhibited high variability among MTPs necessitating site‐specific studies with immediate implications to management. It is very important to understand the local hydrogeochemical and climatic conditions to ensure appropriate environmental measures for their management and conservation.
Empirical Models Based on the Universal Soil Loss Equation Fail to Predict Sediment Discharges from Chesapeake Bay Catchments
Authors: Boomer Kathleen B. , Weller Donald E. , Jordan Thomas E.
Published: January 2008

The Universal Soil Loss Equation (USLE) and its derivatives are widely used for identifying watersheds with a high potential for degrading stream water quality. We compared sediment yields estimated from regional application of the USLE, the automated revised RUSLE2, and five sediment delivery ratio algorithms to measured annual average sediment delivery in 78 catchments of the Chesapeake Bay watershed. We did the same comparisons for another 23 catchments monitored by the USGS. Predictions exceeded observed sediment yields by more than 100% and were highly correlated with USLE erosion predictions (Pearson r range, 0.73–0.92; p < 0.001). RUSLE2‐erosion estimates were highly correlated with USLE estimates (r = 0.87; p < 001), so the method of implementing the USLE model did not change the results. In ranked comparisons between observed and predicted sediment yields, the models failed to identify catchments with higher yields (r range, –0.28–0.00; p > 0.14). In a multiple regression analysis, soil erodibility, log (stream flow), basin shape (topographic relief ratio), the square‐root transformed proportion of forest, and occurrence in the Appalachian Plateau province explained 55% of the observed variance in measured suspended sediment loads, but the model performed poorly (r2 = 0.06) at predicting loads in the 23 USGS watersheds not used in fitting the model. The use of USLE or multiple regression models to predict sediment yields is not advisable despite their present widespread application. Integrated watershed models based on the USLE may also be unsuitable for making management decisions.
Reduction of Pathogen Indicator Organisms in Dairy Wastewater Using an Ecological Treatment System
Authors: Morgan Jennifer A. , Hoet Armando E. , Wittum Thomas E. , Monahan Clifton M. , Martin Jay F.
Published: January 2008

Ecological treatment systems can provide a sustainable, plant‐based alternative to traditional wastewater treatment. One factor essential to the success of these systems is ensuring their ability to reduce coliform concentrations in wastewater. Wastewater is the primary source of fecal contamination in aquatic ecosystems, containing total and fecal coliforms on the order of 108–1010 and 107–109 CFU L−1, respectively. This study assessed the ability of an ecological treatment system to reduce concentrations of total coliforms and Escherichia coli from dairy wastewater. Low strength wastewater was pumped into the system during July of 2005 and high strength in September 2005. Wastewater passes through a series of anaerobic, aerobic, and clarifier reactors and wetland cells before exiting the system. Regardless of wastewater strength, average total coliform and E. coli concentrations were consistently reduced by at least 99% from influent to effluent, with the majority of the reduction (76%) occurring in the first two reactors. Relationships between internal concentrations of solids and coliforms indicated that increased reduction of solids may further reduce coliform concentrations. Although U.S. Environmental Protection Agency discharge requirements for E. coli were not always met, the substantial reductions achieved indicate that ecological treatment systems have the potential to successfully reduce coliforms in wastewater to meet discharge limits. The results from this study will be used to guide design and management of future ecological treatment systems, so that larger and more consistent coliform reductions can be achieved.
Effect of Liquid Swine Manure Rate, Incorporation, and Timing of Rainfall on Phosphorus Loss with Surface Runoff
Authors: Allen Brett L. , Mallarino Antonio P.
Published: January 2008

Excessive manure phosphorus (P) application increases risk of P loss from fields. This study assessed total runoff P (TPR), bioavailable P (BAP), and dissolved reactive P (DRP) concentrations and loads in surface runoff after liquid swine (Sus scrofa domesticus) manure application with or without incorporation into soil and different timing of rainfall. Four replicated manure P treatments were applied in 2002 and in 2003 to two Iowa soils testing low in P managed with corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotations. Total P applied each time was 0 to 80 kg P ha−1 at one site and 0 to 108 kg P ha−1 at the other. Simulated rainfall was applied within 24 h of P application or after 10 to 16 d and 5 to 6 mo. Nonincorporated manure P increased DRP, BAP, and TPR concentrations and loads linearly or exponentially for 24‐h and 10‐ to 16‐d runoff events. On average for the 24‐h events, DRP, BAP, and TPR concentrations were 5.4, 4.7, and 2.2 times higher, respectively, for nonincorporated manure than for incorporated manure; P loads were 3.8, 7.7, and 3.6 times higher; and DRP and BAP concentrations were 54% of TPR for nonincorporated manure and 22 to 25% for incorporated manure. A 10‐ to 16‐d rainfall delay resulted in DRP, BAP, and TPR concentrations that were 3.1, 2.7, and 1.1 times lower, respectively, than for 24‐h events across all nonincorporated P rates, sites, and years, whereas runoff P loads were 3.8, 3.6, and 1.6 times lower, respectively. A 5‐ to 6‐mo simulated rainfall delay reduced runoff P to levels similar to control plots. Incorporating swine manure when the probability of immediate rainfall is high reduces the risk of P loss in surface runoff; however, this benefit sharply decreases with time.
Environmental Risk Assessment of Genetically Engineered Herbicide‐TolerantZoysia japonica
Authors: Bae T. W. , Vanjildorj E. , Song S. Y. , Nishiguchi S. , Yang S. S. , Song I. J. , Chandrasekhar T. , Kang T. W. , Kim J. I. , Koh Y. J. , Park S. Y. , Lee J. , Lee Y.‐E. , Ryu K. H. , Riu K. Z. , Song P.‐S. , Lee H. Y.
Published: January 2008

Herbicide‐tolerantZoysiagrass (Zoysia japonicaSteud.) has been generated previously throughAgrobacterium tumefaciens‐mediated transformation. The genetically modified (GM)Zoysiagrass survived Basta spraying and grew to maturity normally while the wild‐type (WT) grass stopped growing and died. GMZoysiagrass will permit more efficient weed control for various turf grass plantings such as home lawns, golf courses, and parks. We examined the environmental/biodiversity risks of herbicide‐tolerant GMZoysiabefore applying to regulatory agencies for approval for commercial release. The GM and WTZoysiagrass' substantial trait equivalence, ability to cross‐pollinate, and gene flow in confined and unconfined test fields were selectively analyzed for environmental/biodiversity effects. No difference between GM and WTZoysiagrass in substantial traits was found. To assess the potential for cross‐pollination and gene flow, a non‐selective herbicide, Basta, was used. Results showed that unintended cross‐pollination with and gene flow from GMZoysiagrass were not detected in neighboring weed species examined, but were observed in WTZoysiagrass (on average, 6% at proximity, 1.2% at a distance of 0.5 m and 0.12% at a radius of 3 m, and 0% at distances over 3 m). On the basis of these initial studies, we conclude that the GMZoysiagrass generated in our laboratory and tested in the Nam Jeju County field does not appear to pose a significant risk when cultivated outside of test fields.