James L. Walworth

Bioremediation of a Petroleum-Contaminated Cryic Soil: Effects of Phosphorus, Nitrogen, and Temperature

Abstract Bioremediation has been shown to be an effective means of treating petroleum‐contaminated soils in cold areas, although the conditions required to maximize bioremediation in cold region (cryic) soils are not well documented. A laboratory study was conducted to investigate the effects of nitrogen and phosphorus levels and temperature on petroleum bioremediation. A cryic entisol contaminated with diesel fuel was treated with nitrogen (0, 400, 800, or 1200 mg/kg of soil) and phosphorus (0, 60, 120, or 180 mg/kg of soil) and incubated at two temperatures (10 and 20°C). At 10°C, bioremediation rates were not affected by fertility treatments. At 20°C, reaction rates were increased by the addition of P, but unaffected by N. Regardless of fertility regime, the rate of diesel loss was much greater in soil incubated at 20°C than in soil incubated at 10°C.

Enhancement and inhibition of soil petroleum biodegradation through the use of fertilizer nitrogen: An approach to determining optimum levels

Laboratory studies were conducted to evaluate the relationship between soil water content and microbial response to soil nitrogen (N) in petroleum‐contaminated soils. Various levels of N were added to a sand, a sandy loam, and a silt loam. Measurements of the extent of biodegradation in each soil (petroleum loss or CO2 production) indicated that biodegradation was related to soil N expressed as a function of soil water (mg N/kg soil H2O or mg N/I) better than N expressed as a function of soil dry matter (mg N/kg soil). A loamy sand was treated with four levels of N (0, 250, 500, 750 mg N/kg soil) and incubated at three water contents (5.0, 7.5, and 10.0% on a dry soil weight basis). Soil water potential and O2 consumption were best related to N expressed on the basis of soil water. It is concluded that expressing N in units of mg N/kg soil H2O (easily obtained by dividing [mg N/kg dry soil] by [soil moisture content]) can be used to determine fertilization rates for bioremediation processes. On this basis...

Nutrient and temperature interactions in bioremediation of cryic soils

Low temperatures and lack of available nutrients often limit the rate of microbial petroleum hydrocarbon degradation in contaminated cryic soils. Proper management of both these parameters may increase microbial respiration in such soils. Interactions between nutrient level and temperature could impact management decisions for both factors, but these interactions have not previously been adequately described. Petroleum-contaminated soils from two Alaskan sites were studied in separate laboratory experiments. Nutrients and incubation temperatures were independently varied so interactions between the two could be studied. Soil from a gravel pad near Barrow, AK responded positively to temperatures increasing from 5°C to 20°C, and to addition of 50 or 100 mg/kg of supplemental nitrogen. Soil from Ft. Wainwright, AK responded positively as temperatures were increased from 1°C to 21°C, but microbial respiration decreased when temperatures were raised to 41°C. Microbial activity increased when 100 or 200 mg/kg of supplemental nitrogen was applied. In both soils, there were positive interactions between soil temperature response and addition of nitrogen fertilizer. Microbial response to soil warming was accentuated by proper nitrogen management, and response to fertilizer application was greatest when soil was warmed.

A compendium of tissue nutrient concentrations for field-grown potatoes

Current literature was reviewed to evaluate relationships between potato tissue nutrient concentrations and yield. Primary sources (those based on original research) were emphasized to prevent duplicate information. Data were rejected if stage of growth and plant part were not specifically defined. Data that met these criteria were separated by plant part, stage of growth, and nutrient form (soluble versus total nutrient). The information was then compiled to illustrate the range of reported values for each nutrient, stage of growth, and plant part. Values are presented for deficient, low, sufficient, high, and toxic levels of nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, boron, chlorine, copper, iron, manganese, and zinc.CompendioSe revisó la literatura existente para evaluar la relatión entre las concentraciones de nutrientes en los tejidos de papa y el rendimiento. Se enfatizó en las fuentes basicas (aquellas basadas en la investigatión original) para evitar duplicar la informatión. Los datos fueron rechazados si el estado de crecimiento de las partes de la planta no era específicamente definido. Los datos que cumplían con estos criterios fueron separados de acuerdo con la parte de la planta, estado de crecimiento y la forma de nutriente (soluble vs. nutriente total). La información fue luego consolidada para mostrar el rango de los valores reportados para cada nutriente, estado de crecimiento y parte de la planta. Los valores se presentan para niveles deficientes, bajos, suficientes, altos y tóxicos de nitrógeno, fosforo, potasio, calcio, magnesio, azufre, boro, cloro, cobre, hierro, manganeso y zinc.

Tuber initiation and development in irrigated and non-irrigated potatoes

Tuber initiation and development are processes basic to potato production and are particularly critical in areas with short growing seasons. It is important to know how and to what extent management decisions affect these processes in order to maximize the yield of marketable tubers. A two-year field study, conducted in southcentral Alaska, examined top growth, tuber initiation, and tuber development in eight potato cultivars grown with and without irrigation. Plants of the cultivars Allagash Russet, Bake-King, Green Mountain, Kennebec, Lemhi Russet, Russet Burbank, Shepody, and Superior were harvested weekly throughout the growing season, and top dry weight, numbers of tubers, and individual tuber fresh weights were recorded. Top dry weight was reduced by moisture stress shortly after emergence in 1993, and about one month following emergence in 1994, when early-season soil moisture was greater. The weight of tubers was similarly affected within approximately 5 wk of emergence in 1993 and 6 weeks in 1994. Tuber weight at harvest was increased two-to three-fold by irrigation in all cultivars. The number of tubers each plant set was affected by irrigation in most, but not all, cultivars. Some varieties (Lemhi Russet in 1994, Allagash Russet both years) set more tubers than were maintained through the growing season. Tuber remnants found during sample collection indicated that tuber reabsorption had occurred. Irrigated Green Mountain had more than one tuber initiation period during the season, whereas other varieties such as Shepody maintained a relatively constant number of tubers following initial tuber set. Tuber size distribution at the end of the growing season showed that larger tubers were favored by irrigation.ResumenEl inicio y desarrollo de la tuberización son procesos básicos para la producción de papa, y son particularmente críticos en áreas con una corta temporada de crecimiento. Es importante conocer cómo y qué decisiones de manejo afectan dicho proceso con el fin de maximizar el rendimiento de los tubérculos con valor comercial. Un estudio de campo de dos anos, realizado en el centra y sur de Alaska, examinó el crecimiento de los brotes, el inicio de la tuberización y su desarrollo en ocho cultivares con y sin irrigación. Plantas de las variedades Allagash Russet, Bake-King, Green Mountain, Kennebec, Lemhi Russet, Russet Burbank, Shepody y Superior fueron cosechadas semanalmente durante la temporada de crecimiento, registrándose el peso seco de los brotes, el numero de tubérculos y el peso individual de los tubérculos frescos. El peso seco de los brotes se redujo por estrés de humedad poco después de la emergencia en 1993, y cerca de un mes después de la emergencia en 1994, cuando la humedad del suelo al principio de la temporada fue mayor. El peso de los cultivares fue afectado en forma similar durante las cinco semanas de emergencia en 1993 y seis semanas en 1994. El peso de los tubérculos a la cosecha se incrementó dos a tres veces por irrigación en todos los cultivares. El numéro de tubérculos de cada planta fue afectado por la irrigación en la mayor parte, pero no en todos los cultivares. Algunas variedades (Lemhi Russet en 1994, Allagash Russet en ambos años) fijaron más tubérculos que fueron mantenidos durante la estación de crecimiento. Los tubérculos remanentes encontrados durante la recolección de la muestra indicaron que habia ocurrido una reabsorción de tubérculos. La variedad irrigada Green Mountain ténia más de un tubérculo en el periodo de inicio de tuberización durante la temporada, mientras que otras variedades, como Shepody, mantuvieron un numéro de tubérculos relativamente constante después de la fijación de la tuberización inicial. La distribución del tamaño de los tubérculos hacia el fin de la estación de crecimiento demostro que los tubérculos más grandes fueron favorecidos por la irrigación.

Nutrient amendments for contaminated peri-glacial soils: use of cod bone meal as a controlled release nutrient source

The lack of available nutrients, particularly nitrogen, often limits the rate of microbial petroleum hydrocarbon degradation in contaminated cold region soils. Microbial activity in many peri-glacial soils responds to addition of nitrogen, although excess levels can inhibit biodegradation by decreasing soil water potentials. Aqueous soluble inorganic fertilizer quickly partitions into soil water, increasing the salt concentration, and imposing an osmotic potential. Strategies that can be used to avoid microbial inhibition include the use of controlled release fertilizers. We studied the use of an organic fertilizer, cod bone meal, as a nutrient source for bioremediation. Nitrogen mineralization from cod bone meal was greater at 20 °C (first-order reaction rate constant k=0.0206 d -1 ) than at 10 °C (k=0.0154 d -1 ) and greater at pH 6.5 and 7.5 (k=0.0208 and 0.0189 d -1 , respectively) than at pH 5.5 (k=0.0143 d -1 ). Net O 2 consumption from diesel fuel degradation in a contaminated soil was greatly increased by addition of nitrogen and phosphorus in the form of diammonium phosphate (DAP) or cod bone meal relative to unfertilized soil. Cod bone meal fertilized soils had greater net O 2 consumption than DAP fertilized soils. However, residual soil hydrocarbon analyses indicated no difference in petroleum loss between the two nutrient sources.

Biodegradation of Aliphatic vs. Aromatic Hydrocarbons in Fertilized Arctic Soils

The objectives of this study were to (1) test a simple bioremediation treatment strategy in the Arctic and (2) examine the effect of fertilization on the degradation of aliphatic and aromatic hydrocarbons. The site is a coarse sand pad that once supported fuel storage tanks. Concentrations of diesel-range organics at the beginning of the study (July 1996) ranged from 250 to 860 mg/kg soil. Replicate field plots treated with fertilizer yielded final concentrations of 0, 50, 100, or 200 mg N/kg soil. Soil samples were collected three times during the thaw season and analyzed for physical and chemical properties, microbial populations and activities, and concentrations of semivolatile hydrocarbons. Soil pH and soil-water potentials declined as a result of fertilizer application. Addition of fertilizer significantly increased soil respiration potentials, but not the populations of microorganisms measured. Fertilizer addition also resulted in ∼50% loss of measured aliphatic and aromatic hydrocarbons in surface...

Fertigation Frequency for Subsurface Drip-Irrigated Broccoli

Yosef and Sagiv, 1982; Stark et al., 1983; Burt et al., 1995). However, very few studies have shown a benefit Subsurface-drip irrigation and fertigation with fluid N fertilizer of frequent or continuous fertigation compared with sources offers substantial flexibility for N fertilizer management. Fertiless frequent fertigation. Bar-Yosef and Sagiv (1982) gation events can be scheduled as often as irrigation, up to several times per day. However, because of system or management constraints practiced continuous fertigation of surface drip-irrivery frequent fertigation may not be possible or desirable for some gated tomato (Lycopersicum esculentum L.) with congrowers. Optimum fertigation interval for subsurface drip-irrigated centrations of 100 to 200 mg N L 1 in the irrigation crops has not been well researched. A 3-yr field experiment was water. However, this resulted in N applications 1000 conducted on a sandy loam soil in southern Arizona with subsurface kg N ha 1, far greater than N uptake by the plants; drip-irrigated broccoli (Brassica olearacea L. Italica) to i) determine consequently N use efficiency (NUE) was as low as the effects of N rate and fertigation frequency on crop yield, quality, 30%. Stark et al. (1983) determined that 75 mg N L 1 and crop N status, and ii) estimate a N balance. Broccoli was planted was the optimum concentration for continuous fertigain two rows per raised bed 1.02 m apart, with one drip line buried tion of tomato with surface-drip irrigation. Bhella and 0.15 to 0.20 m deep within each bed. The experiment included factorial Wilcox (1985) advocated continuous fertigation of surcombinations of two N rates and four fertigation frequencies (intervals of 1, 7, 14, and 28 d). Broccoli marketable yield and quality were face drip-irrigated cantaloupe (Cucumis melo L.) with responsive to N rate, but not to increased fertigation frequency. Dur150 and 50 mg N L 1 during vegetative and reproductive ing one of three seasons, fertigation frequency significantly (P 0.05) stages, respectively. affected crop N uptake, but there was no trend of increasing N uptake Few studies are reported in which the effects of differwith increasing fertigation frequency. Unaccounted fertilizer N and ent drip-fertigation frequencies on yield and quality of apparent N use efficiency (ANUE) were calculated for two seasons. annual crops are compared. Several researchers have Unaccounted fertilizer N averaged 20 and 75 kg ha 1 and ANUE 90 compared applications of all N soil-applied preplant and 81% with 250 and 350 kg N ha 1 applied, respectively. Neither with a combination of preplant soil-applied and in-seawas significantly affected by fertigation frequency. We conclude, son fertigated N on tomato. Locascio et al. (1985, 1989) therefore, that for broccoli production with subsurface-drip irrigation found that surface drip-irrigated tomato yields were on sandy loam or finer soils, fertigation can be applied as infrequently as monthly, without compromising crop yield or quality, or causing higher with 40% of the N applied preplant and 60% excessive N losses. applied by fertigation, compared with all N applied preplant on sandy soils in Florida. Dangler and Locascio (1990) found that yield of surface drip-irrigated tomato was higher on a fine sand when 50% of fertilizer N M studies have demonstrated drip-irrigated crop response to N (e.g., Bar-Yosef and Sagiv, was soil-applied before planting, than when all N was applied via fertigation. Cook and Sanders (1991) ex1982; Thompson et al., 2002a). Optimum N rates for many drip-irrigated crops have been published (Hochamined the effect of fertigation frequency (daily to monthly) on subsurface drip-irrigated tomato yields in muth, 1992; Hartz, 1994). Drip irrigation and fertigation with fluid N fertilizer sources offer what is probably two South Carolina soils. Daily or weekly fertigation significantly increased yield compared with monthly ferthe ultimate in flexibility for N fertilizer management. Fertigation events can be scheduled as often as irritigation, but there was no advantage of daily over weekly fertigation on a loamy sand. The same fertigagation, up to several times per day. However, because of system or management constraints very frequent tion frequencies resulted in no differences in yield and quality on a loamy fine sand soil. Locascio and Smajstrla fertigation may not be possible or desirable for some growers. Optimum fertigation interval for drip-irrigated (1995) found that surface drip-irrigated tomato yields with daily fertigation were not increased compared with crops, although important, has not been thoroughly researched (Hartz, 1994). yields with weekly fertigation on a fine sand. Locascio et al. (1997) found that there were no differences in Various authors have recommended very frequent or continuous fertigation for drip-irrigated crops (i.e., Baryield or quality of surface drip-irrigated tomato fertigated either six or 12 times per season. Similarly, yields of surface drip-irrigated pepper (Capsicum annum L.) T.L. Thompson, S.A. White, J. Walworth, and G.S. Sower, 429 Shantz, were not affected by fertigation interval (11 or 22 d) on Dep. of Soil, Water and Environmental Science, University of Aria loamy sand soil (Neary et al., 1995). zona, Tucson, AZ 85721. Received 27 June 2002. *Corresponding author (thompson@ag.arizona.edu). Abbreviations: ANUE, apparent N use efficiency; NUE, N use efficiency. Published in Soil Sci. Soc. Am. J. 67:910–918 (2003).

Assessment of C:N Ratios and Water Potential for Nitrogen Optimization in Diesel Bioremediation

ABSTRACT Sandy clay loam soil contaminated with 5000, 10,000 or 20,000 mg/kg of diesel fuel no. 2 was amended with 0 (ambient nitrogen only), 250, 500, or 1000 mg/kg nitrogen (NH4Cl) to evaluate the role of C:N ratios and soil water potential on diesel biodegradation efficacy. The soil was incubated at 25°C for 41 days and microbial O2 consumption measured respirometrically. Highest microbial respiration was observed in the 250 mg N/kg soil treatments regardless of diesel concentration. Higher levels of nitrogen fertilization decreased soil water potential and resulted in an extended lag phase and reduced respiration. Application of 1000 mg/kg nitrogen reduced maximum respiration by 20% to 52% depending on contaminant levels. Optimal C:N ratios among those tested were 17:1, 34:1, and 68:1 for the three diesel concentrations, respectively, and were dependent on contaminant concentration. Nitrogen fertilization on the basis of soil pore water nitrogen (mg N/kg soil H2O) is independent of hydrocarbon concentration but takes into account soil moisture content. This method accounts for both the nutritional and osmotic aspects of nitrogen fertilization. In the soil studied the best nitrogen augmentation corresponded to a soil pore water nitrogen level of 1950 mg N/kg H2O at all diesel concentrations.

Irrigation water quality effects on soil carbon fractionation and organic carbon dissolution and leaching in a semiarid calcareous soil

Irrigation water quality and soil organic matter content influence crop yields and soil properties such as salinity and soil particle aggregation. We used laboratory column and batch studies and soil carbon fractionation to study potential organic carbon (OC) losses from a Typic Torrifluvent with 0.79% total OC and 4.7% inorganic carbon ([IC] as carbonates). About 4% of the total OC fraction was determined to be water-soluble OC (SOC). Under saturated flow, a significant amount of SOC (20%-35%) was lost from this soil (Pima clay loam) with just two pore volumes of irrigation water. Sodium- and sulfate-rich waters and rainwater were up to twice as effective at releasing SOC as waters dominated by calcium and chloride ions. Not all OC losses can be attributed to well-known soil particle dispersive effects of sodium and rainwater. Soluble OC losses were also highly correlated to the progressive dissolution of the soil IC fraction. Water quality has a measurable impact on OC and IC losses from OC-poor carbonate-rich soils. Changes in irrigation water quality may increase OC leaching from the plow layer and favor increased denitrification and potentially carbon sequestration in and below the root zone of irrigated semiarid soils.