bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of BIOLOG for the Analysis of Microbial Communities from Zinc‐Contaminated Soils
Authors: Kelly John J. , Tate Robert L.
Published: July 2010

The BIOLOG procedure, a useful method for assessing differences in community structure between soil microbial communities, could be used to determine the impact of metal contamination of soils and reclamation of these soils; however, high metal levels may affect the results of the BIOLOG assay. This project determined that Zn in soils interfered with extraction of soils with phosphate buffer by forming an insoluble precipitate. High Zn levels were also shown to prevent color formation and to cause false positive readings in the BIOLOG assay. The objectives of this project were developing and validating a modified BIOLOG method for use in the presence of high Zn concentrations. Substitution of 0.1 M Tris buffer for phosphate buffer prevented precipitate formation during the extraction step; however, extraction with Tris buffer could result in high Zn concentrations in the BIOLOG inoculant. Zinc concentrations of >50 mg L−1 in the inoculant were shown to result in false positive readings due to production of a precipitate in the wells. Raising the pH of the extractant to above 7.0 or removal of the Zn with cation exchange resin relieved this problem. Analyses of BIOLOG data showed that neither raising the extractant pH nor using cation exhange resin resulted in observable changes in BIOLOG metabolic profiles. However, use of Tris buffer in place of phosphate buffer did result in a slight change in BIOLOG metabolic profiles. Thus, the nature of the extracting buffer must be considered when analyzing experimental results. The methods developed herein allow use of the BIOLOG procedure for soils with high metal concentrations.
Fluxes of Nitrous Oxide and Molecular Nitrogen from Irrigated Soils of Catalonia (Spain)
Authors: Teira‐Esmatges M. R. , Van Cleemput O. , Porta‐Casanellas J.
Published: July 2010

Nitrous oxide (N2O) is a gas of environmental concern that can be emitted during nitrification and denitrification. Molecular nitrogen (N2) is the ultimate product of denitrification. The emission of both gases represents an economic loss. This study quantified daily and seasonal N2O and N2 emissions from three benchmark arable soils sown with maize (Zea mays L.) in Catalonia (northeast Spain) during the irrigation season, and identified the major factors and processes determining these emissions. The N2O was sampled using the closed chamber method, and N2 from N2O that accumulated with the acetylene inhibition method, simultaneously in the field. At water‐filled pore space (WFPS) >70%, losses amounted to 389 g of N2O‐N ha−1 d−1 from the El Pinell site, 144 g of N2O‐N ha−1 d−1 from the Barbens site, and 125 g of N2O‐N ha−1 d−1 from the Bellpuig site. Most of the N was lost through complete denitrification. Up to 640 g of N2‐N ha−1 d−1 were lost from the El Pinell site, 1438 g of N2‐N ha−1 d−1 from the Barbens site, and 233 g of N2‐N ha−1 d−1 from the Bellpuig site. Negative N2O and N2 fluxes were found. Total (N2O + N2)‐N losses represent 13.6% of the N applied at the El Pinell site, 8.6% at the Barbens site, and 1.7% at the Bellpuig site. Denitrification was the main source of emission. Significant N2O‐N losses due to nitrification were also measured. The potential for gaseous N losses from these soils at <40% WFPS is low (it averaged 0.01 g of N ha−1 d−1 from the three sites).
Phytoaccumulation of Trace Elements by Wetland Plants: I. Duckweed
Authors: Zayed Adel , Gowthaman Suvarnalatha , Terry Norman
Published: July 2010

There has been much interest recently in the use of constructed wetlands for the removal of toxic trace elements from wastewaters. Wetland plants play an important role in the trace elements removal process. It is not known, however, which wetland plant species absorb specific trace elements at the fastest rates. Such knowledge is essential to maximize the efficiency of trace element removal by wetlands. In this study, we investigated the potential of duckweed (Lemna minor L.) to accumulate Cd, Cr, Cu, Ni, Pb, and Se when supplied individually in a nutrient solution at a series of concentrations ranged from 0.1 to 10 mg L−1. The results show that under experimental conditions, duckweed proved to be a good accumulator of Cd, Se, and Cu, a moderate accumulator of Cr, and a poor accumulator of Ni and Pb. The highest concentrations of each trace element accumulated in duckweed tissues were 13.3 g Cd kg−1, 4.27 g Se kg−1, 3.36 g Cu kg−1, 2.87 g Cr kg−1, 1.79 g Ni kg−1, and 0.63 g Pb kg−1. Duckweed exhibited some symptoms of toxicity (e.g., reduced growth, chlorosis) at higher levels of element supply (except for Cr). The toxicity effect of each trace element on plant growth was, in descending order of damage, Cu > Se > Pb > Cd > Ni > Cr. We conclude that duckweed shows promise for the removal of Cd, Se, and Cu from contaminated wastewater since it accumulates high concentrations of these elements. Further, the growth rates and harvest potential make duckweed a good species for phytoremediation activities.
Realizing Basic Research in Applied Environmental Research Projects
Authors: Bouma J.
Published: July 2010

Political pressure is exerted in many countries to focus agricultural and environmental research on market‐driven applications, rather than on basic research. This can become a real problem because our expertise needs to be continuously fed with new ideas originating from basic research. Rather than rigidly oppose the trend, we advocate research procedures where applied and basic research logically fit together in so‐called research chains. More time should be spent in any project on defining the most efficient research chain in close interaction with stakeholders, comparing relatively simple (and inexpensive) procedures using expert knowledge with more complicated (and expensive) ones that may include basic research using sophisticated methodology. Research chains are illustrated for case studies on soil acidification and precision agriculture, while chains are described for organic farming. Basic research is defined differently and more effectively when it is part of a research chain, as compared with independent formulation. Information technology plays an increasingly important role in the evolving interactive research paradigm where the former linear research model is replaced by the hourglass model, which requires an interdisciplinary research approach and defines basic research on issues where existing knowledge is clearly inadequate. Application of simulation modeling and geostatistics allows expression in terms of risks that threshold values of sustainability indicators are exceeded. Regulators have the prime responsibility to decide which risks are acceptable. Researchers offer options rather than judgements. In addition to realizing research chains including basic research, independent funding for basic research in promising future areas of work is necessary as well.
Alachlor Dissipation in Shallow Cropland Soil
Authors: Weed D. A. J. , Kanwar R. S. , Cambardella C. , Moorman T. B.
Published: July 2010

A soil‐column laboratory experiment and a 2‐yr field‐sampling study evaluated the overall dissipation of alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl) acetamide]. Theses studies also measured the effect of no‐till and chisel‐plow tillages on alachlor leaching and dissipation. In the top 30 cm layer of soil, the overall half‐life was 3 d or less, and the time to 90% dissipation ranged from 17 to 30 d. In no‐fill soil, alachlor dissipated slightly faster, and more was transported into the 10 to 30 cm soil layer. Weather conditions promoting the movement of alachlor into the soil, however, weakened the effect of tillage on the dissipation rate. Most of the alachlor present in the soil, regardless of tillage, was found in the top 10 cm at all times. Of the alachlor applied to 30‐cm tall soil columns, only 0.4% was removed by water flowing from chisel‐plow columns and 1.6% from no‐till columns. The results show that tillage was not a key factor in alachlor dissipation and leaching. Alachlor leaching was also a minor component in overall dissipation.
Groundwater Quality under Conventional and No Tillage: II. Atrazine, Deethylatrazine, and Metolachlor
Authors: Masse L. , Patni N. K. , Jui P. Y. , Clegg B. S.
Published: July 2010

The effect of no tillage (NT) and conventional tillage (CT) on the contamination of shallow groundwater by atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine), deethylatrazine (2‐chloro‐4‐amino‐6‐isopropylamino‐s‐triazine), and metolachlor (2‐chloro‐N‐(ethyl‐6‐methylphenyl)‐N‐(2‐metoxy‐1‐methylethyl) acetamide) at nominal depths of 1.2, 1.8, 3.0, and 4.6 m was studied during four successive crop‐years in four corn (Zea mays L.) fields with loam soil. Atrazine and deethylatrazine were almost always present in the shallow groundwater. Atrazine concentrations were below the U.S. Environmental Protection Agency (USEPA) lifetime health advisory (LHA) of 3 µg/L in more than 99% of the 920 groundwater samples from the two tillage treatments. Atrazine concentrations, although low, were significantly higher under NT than CT (P < 0.05) at the 1.8 and 3.0 m depths. Deethylatrazine concentrations were also low but were generally higher than those of the parent compound. They were significantly higher under NT than CT at the 1.2 and 1.8 m depths (P < 0.1), as well as at 3.0 m (P < 0.01). Metolachlor was detected in only 25% of the samples and concentrations were well below the USEPA LHA of 100 µg/L. There was no tillage treatment effect on metolachlor concentration. Results from this study suggest a low potential for serious pollution of shallow groundwater from application of atrazine and metolachlor at agronomically recommended rates in tile‐drained corn fields in cold humid regions under both CT and NT practices. However, atrazine leaching appears to be greater under NT than under CT.
Evaluation of Localized Compaction and Doming to Reduce Anion Leaching Losses Using Lysimeters
Authors: Ressler D. E. , Horton R. , Baker J. L. , Kaspar T. C.
Published: July 2010

Fertilizer N that leaches from the root zone is not available for uptake by plants and can be transported to surface waters by subsurface drains, where it is considered a contaminant. Localized soil compaction and doming (LCD) to divert precipitation or irrigation water around the zone of fertilizer injection may be one way to reduce nitrate (NO−3) leaching from agricultural fields. This study was designed to determine whether anion tracer transport through soil profiles to subsurface drains could be delayed by modified application methods, specifically (i) injection using a conventional knife shank; (ii) broadcast application; and (iii) injection and covering using an LCD injector. Three fluorobenzoate tracers, which move similarly to NO−3 through soil, were applied to eight lysimeters at 63 kg ha−1 using the three application treatments. Each treatment contained an individual tracer. Two rainfall intensity treatments were imposed, four lysimeters per rainfall intensity treatment. All lysimeters received 50 mm of simulated rain 3 d after chemical application. A storm of this magnitude occurs once in 5 yr in Iowa. There were no differences in cumulative tracer leaching between the different rainfall intensity treatments. At the end of 6 mo, 5% of the tracer applied by a conventional knife shank leached to the subsurface drains, 4% applied as broadcast leached, and 1% applied by the LCD leached. At 18 mo, corresponding values were 25, 17, and 13%. These results suggested that soil modification in the fertilizer injection zone was a simple and effective way to reduce anion leaching.
Wind Barriers Suppress Fugitive Dust and Soil‐Derived Airborne Particles in Arid Regions
Authors: Grantz David A. , Vaughn David L. , Farber Robert J. , Kim Bong , Ashbaugh Lowell , VanCuren Tony , Campbell Rich
Published: July 2010

Areas of abandoned agricultural land in the Antelope Valley, western Mojave (high) desert of California have proven in our previous studies to be recalcitrant to conventional tillage and revegetation strategies designed to suppress wind erosion of soil and transport of sediment and fugitive dust. These areas represented a continuing source of drifting sand and of coarse and respirable suspended particulate matter. The traditional techniques failed because furrows collapsed and the water holding capacity of the overburden was too low to support seed germination and transplant survival. In this study a variety of wind barriers were evaluated for suppression of sediment transport. Airborne particles were measured with an array of coarse particle samplers at heights of 0.2, 1.0, and 2.0 m above the soil surface. Discrete artificial wind barriers, consisting of widely spaced roughness elements, were effective in suppressing fugitive emissions (>75% at 0.2 m). Wind fences established along the leeward edge of an area of blowing sand, perpendicular to the prevailing wind, significantly decreased fugitive emissions (>90% at 0.2 m). Control was greatest and precision of the measurements was highest under high wind conditions. These techniques provide rapid and effective suppression of fugitive emissions of soil‐derived particles under conditions that resist conventional tillage and revegetation techniques. A simple, indirect procedure for determining local wind velocity erosion thresholds requiring only sampling of wind run and suspended particulate mass compared favorably with direct measurement of saltation as a function of wind velocity.
Ammonia Volatilization from Surface or Incorporated Biosolids by the Addition of Dicyandiamide
Authors: Quemada M. , Lasa B. , Lamsfus C. , Aparicio‐Tejo P. M.
Published: July 2010

Biosolids management can affect N gaseous losses, and may be an important tool for sludge N management. The objectives of our experiment were to determine the effect of dicyandiamide (DCD) addition and biosolids placement on (i) ammonia volatilization, and (ii) C mineralization and inorganic N accumulation. Biosolids, treated or untreated with DCD, were either surface‐applied or soil‐incorporated at a rate of 31.7 g of dry solids kg−1 soil, and incubated in flasks at 21°C for 62 d. Free air was renewed at 0.15 L min−1 and NH3 and CO2 in the air flowing out of each flask were collected in traps for each treatment. Inorganic N in soil plus biosolids mixtures was determined at the end of the study. Surface‐applied biosolids treated with DCD lost 71% while nontreated biosolids lost 20% of the applied NH+4‐N. Soil‐incorporated biosolids lost <5% of the applied NH+4‐N. Surface placement of the biosolids enhanced C mineralization, while it did not affect inorganic N accumulation. Addition of DCD to the biosolids did not affect C mineralization, but increased the accumulation of inorganic N. These results suggest that addition of DCD and biosolids placement can be used for managing sludge N.
Assessment of Phytoavailability of Nickel in Soils
Authors: Echevarria G. , Morel J. L. , Fardeau J. C. , Leclerc‐Cessac E.
Published: July 2010

Methods are needed for the rapid characterization of the phytoavailable fraction of trace elements in soils to assess the risk of contamination of the food chain and evaluate the impact of waste management practices. This investigation was undertaken to study the phytotavailability of Ni in soils using the isotopic exchange method. Isotopic exchange of 63Ni2+ ions was studied in two soils, a silt loam and a clayey muck, and the isotopic composition of Ni in the soil solution was determined. Plant tests were conducted on the same soils amended with 63Ni2+, and the isotopic composition of Ni in the plant tissues was also measured. The isotopic composition of Ni in soil extracted by DTPA at the end of the culture was also determined. Results showed that the isotopic composition of Ni in the soil solution was identical to the isotopic composition of Ni taken up by plants during the same time. The Ni in the plant came exclusively from the pool of the isotopically exchangeable Ni of the soil. Also, under these experimental conditions, DTPA extracted mainly isotopically exchangeable Ni, reinforcing the validity of this chemical to assess the phytoavailability of Ni. Besides, the phytoavailable soil Ni could be characterized with the intensity, quantity, and capacity factors deduced from isotopic exchange kinetics. The kinetics for which parameters were obtained from short‐term experiments were successfully extrapolated to longer times of exchange corresponding to plant growth which demonstrated that isotopic exchange kinetics is an appropriate tool to assess the truly phytoavailable Ni in soils. This technique requires more data from many different soils before it can be used for routine measurements.
Behavior of the Soil Fumigant Methyl Isothiocyanate in Repacked Soil Columns
Authors: Frick A. , Zebarth B. J. , Szeto S. Y.
Published: July 2010

The environmental fate of the soil fumigant methyl isothiocyanate (MITC) is of concern in areas with groundwater aquifers sensitive to contamination. The objective of this study was to examine the partitioning of soil‐applied MITC among the processes of degradation, adsorption, volatilization to the atmosphere, and leaching from the root zone. Methyl isothiocyanate was injected into repacked soil columns in which leaching loss, volatilization loss, and soil‐extractable MITC were measured, and degradation was calculated by mass balance. The effects of three soil water regimes and four soils with differing clay and organic C contents on MITC behavior were examined. Methyl isothiocyanate degradation was rapid; >90% of applied MITC was degraded in 83 d. Methyl isothiocyanate volatilization loss was positively correlated to soil air‐filled porosity and was suppressed by water application, indicating volatilization was strongly influenced by gas‐phase MITC transport. Under conditions favorable for volatilization, up to 30% of applied MITC volatilized over 35 d. Methyl isothiocyanate retention compared with bromide was relatively small. Methyl isothiocyanate leaching increased with increasing frequency of water application or decreasing delay of water application after MITC injection, and with decreasing degradation and volatilization losses. Under most field conditions, MITC should be removed from the soil root zone by degradation and volatilization before significant leaching occurs. However, because volatilization and degradation losses were very sensitive to soil properties and water regime, site specific soil and climatic conditions immediately after application will have a large influence on MITC leaching potential.
Facilitated Transport of Napropamide by Dissolved Organic Matter in Sewage Sludge‐Amended Soil
Authors: Nelson S. D. , Letey J. , Farmer W. J. , Williams C. F. , Ben‐Hur M.
Published: July 2010

The application of sewage sludge to agricultural soils is practiced to minimize landfill disposal. Organic matter amendments to soil are generally thought to improve soil quality, but pesticide application to these soils may lead to groundwater contamination problems. The complexation of pesticides with a water‐soluble carrier such as dissolved organic matter (DOM) may facilitate chemical movement through soil. Sewage sludge amendments may lead to greater downward movement of organic chemicals if associated with DOM. Napropamide [2‐α‐napthoxy)‐N,N‐diethylpropionamide] was applied to a silt loam soil with (SS) and without (NoSS) sewage sludge application. Laboratory batch equilibrium and soil column studies were performed to determine the potential for herbicide complexation with DOM. Over 98% of the herbicide in soil columns followed typical adsorption and transport behavior as the center of mass of the lower organic matter soil (NoSS) moved twice the depth as that of SS. However, napropamide was detected in the initial leachate eluted from repacked soil columns with steps taken to prevent preferential flow. Napropamide concentrations in the initial leachate of SS were twice that from NoSS with <1.5% of the total applied chemical mass eluting from the bottom of each column. A strong positive relationship was found between napropamide concentration and DOM content in soil leachates. Equilibrium dialysis methods were used to determine that napropamide moving through the soil columns was complexed with DOM. The results show that DOM can facilitate herbicide movement through soil and that sewage sludge‐derived DOM may lead to enhanced chemical transport in sludge‐amended soils.
Assessment of Plant Available Nutrients in Organic Products using an Airlift Bioreactor
Authors: Velthof G. L. , Van Beusichem M. L. , Raijmakers W. M. F. , Janssen B. H.
Published: July 2010

Waste products can be diverted from landfill and used as fertilizer when the nutrient availability in these products can be reliably determined. The aim of this study was to determine whether aerobic incubation in an internal‐loop airlift bioreactor is a reliable method for assessing plant‐available N and P in organic waste products. Published results of pot experiments with ryegrass were used as a reference for available N and P. The incubation in the airlift reactor was also compared with conventional incubation in polyethylene bags. Samples of eight different organic products were incubated for 20 d in airlift reactors maintained at pH 5. The plant‐available N fraction was determined by measuring inorganic concentrations in the reactor solution, and the plant‐available P fraction was determined by extraction of P from the solution using iron oxide‐coated filter paper. The available N fraction in the organic products as determined in the airlift reactor was closely related (R2 = 0.73) with the N uptake by ryegrass (Lolium perenne L.). For P, there was no relationship between the P extracted in the airlift reactor and the P uptake by ryegrass. The incubation in the airlift reactors to assess plant‐available N in organic waste products was more rapid than the pot experiment with ryegrass and was more reliable than the conventional incubation in polyethylene bags. We recommend that plant‐available N and P be determined in different airlift reactors, because of possible pH‐related P dissolution and because the iron oxide‐coated filters contain NH4+ which may hamper determination of N.
Regulation of Organic Matter Decomposition and Nutrient Release in a Wetland Soil
Authors: McLatchey G. P. , Reddy K. R.
Published: July 2010

In wetland soils, the supply of O2 to soil is greatly reduced; thus, alternate electron acceptors must be utilized by the microbial populations during decomposition of organic matter. These changes in the supply of electron acceptors affect the size of microbial populations, enzyme production, and decomposition of organic matter. A laboratory study was conducted to determine the role of redox potential (Eh) and availability of electron acceptors on selected microbial processes regulating organic matter decomposition and nutrient release. Soil Eh was maintained approximately at 620, 310, −100, and −220 mV, with the addition of O2, NO−3, SO2−4, and HCO−3, respectively. The soil microbial biomass, as determined by fumigation‐extraction methods, gradually decreased as soils became more reduced. Microbial biomass C ranged from 354 to 10 100 mg C kg−1 soil (dw), while microbial biomass N and P ranged from 140 to 439 mg N kg−1 soil (dw), and 64 to 180 mg P kg−1 soil (dw), respectively. Organic C, N, and P mineralization rates decreased as soils became more reduced. Organic C mineralization rates measured by CO2 production ranged from 51 to 400 mg C kg−1 (dw) d−1. Corresponding values of organic N and P mineralization rates ranged from 21 to 150 mg N kg−1 (dw) d−1, and 6 to 107 mg P kg−1 (dw) d−1, respectively. Significant relationships (P < 0.01) were observed among the soil enzyme activities, microbial biomass, and the mineralization rates of C, N, and P.
Recovery of Biosolids‐Applied Heavy Metals Sixteen Years after Application
Authors: Sloan J. J. , Dowdy R. H. , Dolan M. S.
Published: July 2010

Little is known of the long‐term fate of biosolids‐applied heavy metals in soil. The objective of this study was to quantify percent recovery of biosolids‐applied heavy metals in a well‐drained soil. Three annual applications of biosolids resulted in cumulative biosolids loadings of 0, 60, 120, and 180 Mg ha−1. Cumulative metal loadings for the 180 Mg ha−1 biosolids rate were 25, 141, 127, 43, 173, and 348 kg ha−1 for Cd, Cr, Cu, Ni, Pb, and Zn, respectively. Soils were sampled to a depth of 0.9 m. Soil organic carbon (OC) was measured. Soil was extracted with 1 M HNO3 and metals were determined in the supernatants. Soil OC concentrations were linearly correlated to biosolids loadings and did not change significantly during the 16 yr after biosolids applications. Concentrations of extractable Cd, Cr, Cu, Ni, Pb, and Zn in biosolids‐treated soils were much greater than the control to a depth of 0.30 m (P < 0.01), slightly greater at 0.30 to 0.45 m (P < 0.05) and same as the control below 0.45 m. For the 180 Mg ha−1 biosolids loading, percent recoveries for Cd, Cr, Cu, Ni, Pb, and Zn were 112, 59, 119, 114, 102, and 97%, respectively. Low recovery of Cr was probably due to incomplete extraction from the soil. These results show that complete recovery of biosolids‐applied heavy metals is possible when plot size is large enough to prevent cross‐mixing of treated soils during tillage operations and when sediment losses are minimal.
Sorption and Desorption of Atrazine by Sludge‐Amended Soil: Dissolved Organic Matter Effects
Authors: Celis R. , Barriuso E. , Houot S.
Published: July 2010

Addition of insoluble and soluble organic C to soil through management practices, such as sewage sludge (SS) application, may greatly alter pesticide sorption‐desorption in soil. Batch equilibrium techniques were used to determine the effects of four sewage sludges (liquid‐SS, solid‐SS, limed‐SS, and composted‐SS) and their water dissolved organic matter (DOM), on the sorption‐desorption of atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine) by a silt loam soil. Atrazine sorption on the sludges increased in the order: iimed‐SS < liquid‐SS < solid‐SS < composted‐SS. Sludge addition to soil increased atrazine sorption in the same order, although the effectiveness of the mixtures to sorb atrazine was lower than expected from the sorption capacity of the isolated soil and sludges. The effects of the DOM extracted from the different sludges on atrazine sorption varied with sewage sludge. For liquid‐, solid‐, and limed‐SS, DOM reduced atrazine sorption on soil. A low association between these DOMs and atrazine was measured in solution by dialysis technique, and indicated that processes at the soil/solution interface may have contributed to reduce atrazine sorption. In contrast, enhanced atrazine sorption in the presence of DOM extracted from composted‐SS indicated atrazine was bound by DOM associated with the soil. Atrazine desorption from soil increased in the presence of DOM from all four sludges; however, DOMs had little effect on atrazine desorption from sludge and from sludge‐amended soil. Interactions of soil surfaces with organic amendments and their DOM are shown in this work as a major process determining atrazine sorption‐desorption in amended soil.
Evaluation and Comparison of Five Simulation Models for Estimating Water Drainage Fluxes under Corn
Authors: Jabro J. D. , Toth J. D. , Fox R. H.
Published: July 2010

The simulation accuracies of five water quality models, LEACHW, MACRO, NCSWAP, SLIM, and SOIL to predict the amount of drainage water were evaluated and compared to field data from a 5‐yr leaching experiment. The study was conducted on Hagerstown silt loam soil (fine, mixed, mesic Typic Hapludalf). Drainage fluxes below the rooting zone of corn were measured with pan lysimeters in 1988–1989, 1989–1990, 1990–1991, 1991–1992, and 1992–1993. A series of 18 zero‐tension pan lysimeters (0.465 m2 area) were installed at a depth of 1.2 m to collect drainage water at approximately the rooting depth of corn. All five models were calibrated to the site conditions using data from 1989 to 1990. The calibrated inputs were then used to evaluate the models' simulating accuracy using 1988–1989, 1990–1991, 1991–1992, and 1992–1993 drainage data. The cumulative annual simulations of drainage water from each model were compared to the mean of pan efficiency corrected measured data for these five sampling years. Simulated results for all five models fell within 95% confidence intervals of the measured data. Validation simulations of drainage fluxes were about as accurate as calibration simulations. The statistical analyses indicated that all five models performed well and have the potential to accurately predict the amount of drainage fluxes below the 1.2 m depth under corn cropping system without the need to calibrate the model for each year. There were small differences among the overall performances of the models for simulating drainage losses, but these differences were not significant using one‐way analysis of variance.
Harvest Impacts on Forest Outflow in Coastal North Carolina
Authors: Lebo Martin E. , Herrmann Robert B.
Published: July 2010

Ditch networks are common in coastal North Carolina to improve drainage necessary for crop and timber production. Forest outflow at three locations in a managed loblolly pine (Pinus taeda L.) forest with artificial drainage was monitored during 1986 to 1994 to evaluate how harvest and other normal silvicultural operations affect annual and seasonal outflow characteristics. Increased outflow and small increases in nutrient concentrations occurred following tree harvest; N concentrations for inorganic and organic fractions increased by 0.09 to 0.14 and 0.24 to 0.26 mg L−1, respectively, while total P increased by 0 to 0.07 mg L−1. For a 3‐yr period beginning at harvest, increases in annual outflow, N export, and P export were 111 to 164 mm, 2.1 to 2.2 kg N ha−1 yr−1, and 0.12 to 0.36 kg P ha−1 yr−1, respectively, compared with baseline levels. Outflow and nutrient concentrations returned to baseline levels within 2 to 3 yr. Negligible change in the total suspended solids (TSS) concentration occurred following harvest and site preparation. On a landscape scale, these relatively small increases in annual nutrient exports associated with harvest and site preparation are further reduced to 4 to 7% above baseline levels when placed in the context of a 30‐ to 35‐yr growth cycle for loblolly pine in coastal North Carolina.
Interaction between Manure and Tillage System on Phosphorus Uptake and Runoff Losses
Authors: Ginting D. , Moncrief J. F. , Gupta S. C. , Evans S. D.
Published: July 2010

Application of manure on soils having high P test has raised concerns over the eutrophication of lakes and rivers. The objective of this study was to evaluate the effects of one time application of 164 kg P ha−1 from solid beef (Bos taurus L.) manure on soil Olsen P dynamics, P uptake by corn (Zea mays L.) grain, and P losses as total P (TP), particulate P (PP), and dissolved molybdate reactive P (DMRP) in both snowmelt and rainfall runoff under ridge tillage (RT) and moldboard plow (MP) systems from 1992 to 1994. Soil P was consistently higher in the manure than no manure treated plots (17.9 vs. 12.3 mg kg−1 in 1993 and 23.7 vs. 13.8 mg kg−1 in 1994). Phosphorus uptake was greater from the manure than no manure treated plots (24.5 vs. 19.8 kg ha−1 and 23.5 vs. 18.8 kg ha−1). Annual PP and TP losses were either similar or lower from manure than no manure treated plots. Particulate P losses by rainfall runoff were lower from the RT vs. MP systems (0.25 vs. 1.95 kg ha−1 in 1993 and 0.06 vs. 0.65 kg ha−1 and 1994). The opposite was apparent for DMRP losses in snowmelt, which were higher from the RT than MP system (0.11 vs. 0.01 kg ha−1 and 0.14 vs. 0.03 kg ha−1). The RT system is an environmentally better system than the MP system due to its substantial reduction in annual PP and TP losses.
Biogeochemical Characteristics of the Everglades Sloughs
Authors: Vaithiyanathan Panchabi , Richardson Curtis J.
Published: July 2010

Everglades sloughs are alkaline hardwater systems. Mean water column dissolved phosphate (5 µg/L) and TP (9 µg/L) concentrations in the sloughs are typical of oligotrophic waters. Molar ratios of dissolved inorganic N and P (DIN:DIP = 28:1) in the surface waters suggest that P may be limiting the aquatic primary productivity in the Everglades sloughs. Variations in water column TP and TN in the sloughs were inversely related to the water depth fluctuations (P <0.0001) suggesting a strong link with hydrology. Periphyton and macrophytes in the sloughs exhibited N/P ratios indicative of depletion in P relative to N. The N/P ratios in the Everglades slough communities were in the upper range of values reported for aquatic plants from other ecosystems. The N/P ratios in periphyton were higher than macrophytes suggesting that P depletion was even greater for periphyton. As a result any introduced inorganic phosphate was taken up rapidly by the periphyton reducing the water column PO4‐P to near background levels. Our results suggest that C/N/P ratios of the periphyton provide a reliable measure of the P‐status of the Everglades sloughs whereas the water column P concentration may not truly reflect the P‐status of the system. Periphyton mat also plays an important role in oxygenating the water column of the sloughs. Experimental results show that a decline in periphyton mat cover will result in a decrease in the water column dissolved oxygen concentration and may also lead to other ecosystem changes by enhancing the PAR availability to the slough bottom.
Biodegradation of 2,4‐D in a Noncontaminated Grassland Soil Profile
Authors: Shaw Liz J. , Burns Richard G.
Published: July 2010

Prediction of groundwater contamination and the development of rational bioremediation strategies require a greater understanding of xenobiotic biodegradation at the soil profile scale. We studied 2,4‐dichlorophenoxyacetic acid (2,4‐D) biodegradation for up to 83 d in soil samples collected in 10‐cm depth increments from a noncontaminated soil profile (0–50 cm), and examined factors that influenced biodegradation in the subsoil (40–50 cm). For the four samples collected from 0 to 40 cm, total evolution of 14CO2 from 14C‐ring‐UL‐2,4‐D (20 mg kg−1, 0.25 MBq kg−1) was 50.02 to 60.46% (maximum rate = 4.84% d−1 at 10–20 cm) at the end of the mineralization phase. Subsoil (40–50 cm) mineralization was either 5.47% (maximum rate = 0.113% d−1) or 56.1% (maximum rate = 2.67% d−1) after 83 d. Enhanced mineralization of successive 2,4‐D applications was recorded in all topsoil (0–10 cm) samples and in the subsoil replicates that initially mineralized > 50%. Measurements of 2,4‐D disappearance and most probable number analysis corresponded well with the biodegradation data. Inoculation of subsoil with topsoil (10%) increased 2,4‐D mineralization in the 5% soil to > 50%, whereas amendment with N, P, K, and/or organic C sources (acetate, catechol, vanillin, 3,5‐dihydroxybenzoic acid) did not. We conclude that the subsoil contained a low number of unevenly distributed microorganisms capable of using 2,4‐D as a source of C and energy such that not all the subsamples had competent microorganisms present.
Biodegradation‐Transport Interactions of Pulse Applied 2,4‐D in Repacked Soil Column Microcosms
Authors: Shaw Liz J. , Burns Richard G.
Published: July 2010

To predict leaching to groundwater, reliable data are needed regarding the in situ biodegradation of pesticides. Repacked soil column microcosms were used to examine the transport and biodegradation of 2,4‐dichlorophenoxyacetic acid (2,4‐D) in a noncontaminated soil profile. For columns spiked with 2,4‐D (2.4 mg) and leached with 1.81 cm d−1, maximum leachate concentrations were 4.65 mg L−1. After 30 d, 41.0% was recovered in the leachate and <0.04% by soil extraction. 2,4‐D biodegradation and the distribution and abundance of degrading microorganisms was determined by the leaching rate and the number of herbicide applications. For example, biodegradation of repeat 2,4‐D applications was enhanced: the first and second applications were degraded by 44.5 and 72.6%, respectively. This corresponded to a >103‐fold increase in numbers of 2,4‐D‐degraders at all depths following the first application. A twofold reduction in the irrigation rate also increased biodegradation from 44.5 to 77.2%. Columns of different lengths were used to quantify in situ biodegradation for discrete soil profile sections (10 cm). Subsoil biodegrdadation was higher (43.0%) in columns than it was in batch ex situ experiments (22.3%) after 30 d. The detection of 2,4‐D‐degraders in column subsoil and leachate suggests that downward transport of degrading microorganisms through the soil profile occurs, and could account for discrepancy between batch and column data.
Fecal Bacteria Survival and Infiltration through a Shallow Agricultural Soil: Timing and Tillage Effects
Authors: Stoddard C. S. , Coyne M. S. , Grove J. H.
Published: July 2010

Human and livestock exposure to fecal pathogens via contaminated surface or groundwater is an important water quality concern for soils receiving animal wastes. The effects of manure application timing (spring or fall application) and soil management (no‐tillage or conservation tillage) on fecal bacteria infiltration through shallow karst soils in central Kentucky (the Bluegrass region) have not been evaluated. We performed a field experiment to measure fecal coliforms and fecal streptococci in leachate from dairy manure‐amended no‐tillage and conservation tillage soils. Manure significantly increased fecal bacteria in leachate compared with unmanured treatments. After manure application, the leachate that collected in zero‐tension lysimeters 90 cm below the soil surface contained up to 6 × 104 fecal coliforms/100 mL and generally exceeded 3 × 103 fecal coliforms/100 mL. Neither the timing nor the tillage method significantly affected fecal coliform concentrations in leachate. Fecal bacteria in leachate declined to nondetectable levels within 60 d of manure application. In the well structured soil used in this experiment, fecal bacteria moved below the crop root zone whenever there was rainfall of sufficient duration or intensity to cause flow after manure application. Manure application to no‐tillage soil in spring did not accelerate water contamination by fecal coliforms relative to fall manure applications. No‐tillage did not accelerate water contamination by fecal coliforms relative to tilled soils. The potential for groundwater contamination depended on soil structure and water flow more than on fecal bacteria survival at the soil surface.
Simulating Climate Change Effects in a Minnesota Agricultural Watershed
Authors: Hanratty Michael P. , Stefan Heinz G.
Published: July 2010

The effect of climate change on quality and quantity of runoff from a northern, agricultural watershed was simulated using the Soil and Water Assessment Tool, 1996 Version (SWAT96). SWAT's snow evaporation submodel was modified. SWAT was calibrated using water quality and quantity data measured in the Cottonwood River near New Ulm, MN (drainage area: 3400 km2). The standard errors after calibration were 3.31 mm, 157 kg/d, 752 kg/d, 3744 kg/d, and 85 t/d for mean monthly streamfiow, P yield, ammonia (NH3)/organic N yield, nitrate (NO3) yield, and sediment yield, respectively. The standard error for monthly streamflow was 9.62 mm. SWAT96 was then used to simulate the effect on the Cottonwood River watershed of a 2xCO2 climate scenario, obtained from the Canadian Climate Center's global circulation model. Assuming land cover and land management remained constant, SWAT96 projected a decrease in mean annual streamflow, P yield, NH3/organic N yield, NO3/nitrite (NO2) yield, and sediment yield. Mean monthly values changed significantly for many months of the year under the 2xCO2 climate scenario. The standard errors in SWAT's baseline simulations, however, were too high for the simulated climate change effects to be measurable for NO3/NO2 and sediment yields. The model assumptions and calibration methods used to obtain the accuracy required for simulating the effects of climate change lead to the conclusions that land use/land cover and land management practices are likely to have a greater impact on water quality than climate change and that SWAT must be calibrated to be used for climate change analysis.
Natural Environment and Human Culture: Defining Terms and Understanding Worldviews
Authors: McIsaac G. F. , Brün M.
Published: July 2010

The terms nature and natural each have several different meanings, which can lead to confusion in communications about environmental issues. One approach to clarifying discussion, frequently used in the sciences, is to develop precise, operational definitions of terminology. We argue that this approach can be ineffective when applied to multi‐faceted conceptual terms such as nature, natural, and culture. We think the range of legitimate meanings for these terms may be better communicated by historical accounts of use that describe the assumptions, contexts, and woridviews associated with different interpretations. These accounts do not resolve disagreement but can help clarify the basis for it, and open up new avenues of inquiry. In this paper, we examine the terms nature, natural environment, environmental change, and environmental degradation. A recent article in this journal offered precise definitions of the last three of these terms that were based on the idea that natural is that which is relatively uninfluenced by human culture. Although this is a commonly accepted meaning of natural, we contend that this meaning needs to be carefully scrutinized. We identify specific problems with this usage and offer an account of use of the term nature, which we think provides a more thorough understanding of how nature and natural have been used and understood in different contexts. Since the term natural can be understood several different ways, communication of any particular meaning requires careful articulation of the intended meaning in light of several alternative interpretations.
Water Quality in Walnut Creek Watershed: Nitrate‐Nitrogen in Soils, Subsurface Drainage Water, and Shallow Groundwater
Authors: Cambardella C. A. , Moorman T. B. , Jaynes D. B. , Hatfield J. L. , Parkin T. B. , Simpkins W. W. , Karlen D. L.
Published: July 2010

Nonpoint source contamination of surface and groundwater resources with nitrate‐N (NO3‐N) has been linked to agriculture across the midwestern USA. A 4‐yr study was conducted to assess the extent of NO3‐N leaching in a central Iowa field. Water flow rate was monitored continuously and data were stored on an internal datalogger. Water samples for chemical analysis were collected weekly provided there was sufficient flow. Twelve soil cores were collected in spring, early summer, mid‐summer, and after harvest for each of the 4 yr. Nitrate‐N concentrations in shallow groundwater exhibited temporal trends and were higher under Clarion soil than under Okoboji or Canisteo soil. Denitrification rates were two times higher in Okoboji surface soil than in Clarion surface soil and the highest denitrificafion potential among subsurface sediments was observed for deep unoxidized loess. Soil profile NO3‐N concentrations decreased with depth and were the same below 30 cm for fertilized corn (Zea mays L.) and soybean (Glycine max L. Merr.). Nitrate‐N concentrations in subsurface drainage water exceeded 10 mg L−1 for 12 mo and were between 6 and 9 mg L−1 for 32 mo during the 4‐yr study. The temporal pattern of NO3‐N concentrations in subsurface drainage water was not related to the timing of fertilizer N application or the amount of fertilizer N applied. Total NO3‐N losses to subsurface drains were greatest in 1993 (51.3 kg ha−1) and least in 1994 (4.9 kg ha−1). Most of the subsurface drainage water NO3‐N was lost when crop plants were not present (November‐May), except in 1993. Our results indicate that NO3‐N losses to subsurface drainage water occur primarily as a result of asynchronous production and uptake of NO3‐N in the soil and the presence of large quantifies of potentially mineralizable N in the soil organic matter.
Transport of Nicosulfuron in Soil Columns
Authors: Gonzalez Javier , Ukrainczyk Ljerka
Published: July 2010

Nicosulfuron (2‐[[[[(4,6‐dimethoxy‐2‐pyrimidinyl)amino]carbonyl]amino]sulfonyl]‐N,N‐dimethyl‐3‐pyridinecarboxamide) is a relatively new sulfonylurea promoted for weed control in corn (Zea mays L.). However, there are no published studies on its transport and mobility in soils. In this study, breakthrough curves (BTCs) were measured using soil columns for eight Iowa soils and four Oxisols from Brazil. Chloride (Cl−) and pentafluorobenzoic acid (PFBA) were used as nonreactive tracers. For the sandy Iowa soils and the Brazilian soils BTCs were symmetrical, while for the nonsandy Iowa soils BTCs were asymmetrical. Breakthrough curves were interpreted using convection‐dispersion equation and equilibrium and nonequilibrium transport models. In Brazilian soils and sandy Iowa soils equilibrium models described the BTCs well. In nonsandy Iowa soils, where tailing was observed, the data were better described by a two‐site/two‐region model, indicative of nonequilibrium processes. A comparison with the Cl− and PFBA BTCs suggests that the nonequilibrium is not transport‐related. This is also supported by the low correlation between the mass transfer parameters and the partition coefficients. It is proposed that the observed nonequilibrium in nonsandy Iowa soils is most likely due to nicosulfuron chemisorption on smectites. The results of this study indicate that due to rapid sorption of nicosulfuron on smectites its potential to leach to the groundwater should be relatively low in the loamy and clayey soils that contain expandable 2:1 layer silicates.
Leaching of Broadcast and Banded Atrazine from Maize Plots
Authors: Guillard Karl , Warner Glenn S. , Kopp Kelly L. , Stake Jonathan D.
Published: July 2010

There are few reports that compare losses of atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methyethyl)‐1,3,5‐triazine‐2,4‐diamine] from band and broadcast applications. A field study was conducted in Connecticut to determine the leaching losses of atrazine when applied to maize (Zea mays L.) in 15‐cm bands over the rows or broadcast onto the entire plot. Estimates of leaching losses were made with zero‐tension pan lysimeters. The experiment was set out as a randomized complete block design with four replicates and treatments were method of application (broadcast vs. band) and location of lysimeters (row vs. interrow). Water samples were analyzed for atrazine and related s‐triazines using enzyme‐linked immunosorbent assay (ELISA). There was a greater (P < 0.01) frequency of water samples with atrazine detections from the broadcast application (>99%) than from the band application (82%). Atrazine concentrations also were more likely (P < 0.01) to be above the maximum contaminant level (MCL) of 3 µg L−1 from broadcast treatments (7.1%) than from band treatments (0.7%). Concentrations and mass loss of atrazine were three to four times greater (P < 0.05) in the broadcast treatment than in the band treatment. There were significant (P < 0.05) differences in concentrations and mass losses of atrazine between row and interrow locations of lysimeters for band application but not for broadcast application. Maize yield was not reduced by band atrazine application with interrow cultivation. There is less potential of groundwater contamination from atrazine when applied in a band than when applied broadcast.