RESUMO
Many pharmaceuticals are present in reclaimed wastewater and effluent-dominated water bodies used to irrigate edible crops. Previous research has shown that plants irrigated with reclaimed wastewater can accumulate pharmaceuticals. However, plant-driven processes that contribute to differences in accumulation among compounds are not well understood. Here, we tested the effects of exposure to mixtures on spinach accumulation and metabolism of four psychoactive pharmaceuticals found in reclaimed wastewater: carbamazepine, fluoxetine, amitriptyline, and lamotrigine. Coexposure of plants to carbamazepine and fluoxetine or amitriptyline decreased accumulation of the toxic carbamazepine metabolite 10,11-epoxycarbamazepine. Furthermore, we tested a simple transpiration-based accumulation model and found that transpiration is a strong predictor for accumulation of the studied compounds. Amitriptyline accumulated to a larger extent than predicted from transpiration alone, and we suggest the possibility that a transporter protein may be involved in its uptake. Our findings highlight the need to consider plant physiology and mixture effects in studying accumulation of polar and ionizable organic contaminants and their metabolites.
Assuntos
Poluentes do Solo , Poluentes Químicos da Água , Carbamazepina , Produtos Agrícolas , Spinacia oleracea , Águas ResiduáriasRESUMO
Agricultural nutrient management is an issue due to N and P losses from fields and water quality degradation. Better information is needed on the risk of nutrient loss in runoff from dairy manure applied in winter. We investigated the effect of temperature on nutrient release from liquid and semisolid manure to water, and of manure quantity and placement within a snowpack on nutrient release to melting snow. Temperature did not affect manure P and NH-N release during water extraction. Manure P release, but not NH-N release, was significantly influenced by the water/manure solids extraction ratio. During snowmelt, manure P release was not significantly affected by manure placement in the snowpack, and the rate of P release decreased as application rate increased. Water extraction data can reliably estimate P release from manure during snowmelt; however, snowmelt water interaction with manure of greater solids content and subsequent P release appears incomplete compared with liquid manures. Manure NH-N released during snowmelt was statistically the same regardless of application rate. For the semisolid manure, NH-N released during snowmelt increased with the depth of snow covering it, most likely due to reduced NH volatilization. For the liquid manure, there was no effect of manure placement within the snowpack on NH-N released during snowmelt. Water extraction data can also reliably estimate manure NH-N release during snowmelt as long as NH volatilization is accounted for with liquid manures for all placements in a snowpack and semisolid manures applied on top of snow.
Assuntos
Esterco , Nitrogênio/análise , Fósforo/análise , Agricultura , Indústria de Laticínios , Estações do Ano , Neve , TemperaturaRESUMO
Agricultural phosphorus (P) management is a research and policy issue due to P loss from fields and water quality degradation. Better information is needed on the risk of P loss from dairy manure applied in winter or when runoff is imminent. We used the SurPhos computer model and 108 site-years of weather and runoff data to assess the impact of these two practices on dissolved P loss. Model results showed that winter manure application can increase P loss by 2.5 to 3.6 times compared with non-winter applications, with the amount increasing as the average runoff from a field increases. Increased P loss is true for manure applied any time from late November through early March, with a maximum P loss from application in late January and early February. Shifting manure application to fields with less runoff can reduce P loss by 3.4 to 7.5 times. Delaying manure application when runoff is imminent can reduce P loss any time of the year, and sometimes quite significantly, but the number of times that application delays will reduce P loss is limited to only 3 to 9% of possible spreading days, and average P loss may be reduced by only 15% for winter-applied manure and 6% for non-winter-applied manure. Overall, long-term strategies of shifting manure applications to low runoff seasons and fields can potentially reduce dissolved P loss in runoff much more compared with near-term, tactical application decisions of avoiding manure application when runoff is imminent.
Assuntos
Agricultura , Esterco , Fósforo/análise , Qualidade da Água , Estações do Ano , Movimentos da ÁguaRESUMO
Crops irrigated with reclaimed wastewater or grown in biosolids-amended soils may take up pharmaceuticals and personal care product ingredients (PPCPs) through their roots. The uptake pathways followed by PPCPs and the propensity for these compounds to bioaccumulate in food crops are still not well understood. In this critical review, we discuss processes expected to influence root uptake of PPCPs, evaluate current literature on uptake of PPCPs, assess models for predicting plant uptake of these compounds, and provide recommendations for future research, highlighting processes warranting study that hold promise for improving mechanistic understanding of plant uptake of PPCPs. We find that many processes that are expected to influence PPCP uptake and accumulation have received little study, particularly rhizosphere interactions, in planta transformations, and physicochemical properties beyond lipophilicity (as measured by Kow). Data gaps and discrepancies in methodology and reporting have so far hindered development of models that accurately predict plant uptake of PPCPs. Topics warranting investigation in future research include the influence of rhizosphere processes on uptake, determining mechanisms of uptake and accumulation, in planta transformations, the effects of PPCPs on plants, and the development of predictive models.
Assuntos
Cosméticos/metabolismo , Produtos Agrícolas/metabolismo , Raízes de Plantas/metabolismo , Poluentes Químicos da Água/metabolismo , Modelos Biológicos , Preparações Farmacêuticas/metabolismoRESUMO
is a waterborne pathogen known to have a significant reservoir in bovine manure. Land-dependent manure disposal may not result in significant or reliable pathogen attenuation and, therefore, presents a risk for transport of pathogenic spp. to groundwater. One factor missing in the existing literature is the role soil characteristics play in affecting oocyst transport. Of specific concern in regions with carbonate geology are macropores and other soil structures that contribute to preferential flow. Therefore, research is needed to understand soil type effects and important transport pathways for pathogens such as oocysts to drinking water wells. This study investigated transport potential in several soils overlying Wisconsin's vulnerable carbonate aquifer and related the soil transport to soil series and textural class. Experimental work involved monitoring the transport of oocysts through intact soil columns of different soil series under simulated rain conditions. Results demonstrate that a significant portion of oocysts will sorb or be physically entrapped in the soil, especially in soil with high clay content. However, silt loam soils with comparatively lower clay content demonstrated an ability to transport oocysts through the soil profile primarily via the first flush of water infiltrating through soil macropores. The rate of oocyst migration in silt loam soils paralleled the bromide tracer front, thus bypassing the soils' ability to strain or adsorb oocysts out of infiltrating water. Nevertheless, proper manure treatment and management are necessary to minimize public health risks.
Assuntos
Água Subterrânea , Esterco , Oocistos , Microbiologia do Solo , Animais , Carbonatos , Bovinos , Solo , Movimentos da Água , WisconsinRESUMO
Both the high phosphorus (P) content and P bioavailability of the animal feed coproducts of the corn-ethanol industry could potentially contribute to increased manure and soil P levels and associated environmental issues (e.g., eutrophication). Therefore, a detailed modeling of total P mass flow to the coproducts (i.e., dry distillers grains with solubles, DDGS) was performed. Distribution of P between inorganic P and phytase-hydrolyzable P forms was quantified for selected coproducts (thin stillage, DDGS, modified DDGS [mDDGS]). The P mass balance indicated that although corn is the major P contributor to the coproducts (80.2%), a substantial portion (19.4%) comes from yeast addition. Of the two components constituting DDGS, wet distillers grains and condensed solubles, the latter contributes to only one-third of the mass but, importantly, yields 70.9% of P. The phytase enzyme used, , was very effective in hydrolyzing the nonorthophosphate P components of thin stillage, DDGS and mDDGS. Our results would help track P movement during various dry-grind processing steps and formulate strategies for phytase enzyme supplementation to various postfermentation coproducts from corn-ethanol plants.
Assuntos
Fósforo/química , Zea mays/química , Animais , Bovinos , Etanol/síntese química , Feminino , Masculino , Compostos de Fósforo/análise , Ácido Fítico/análiseRESUMO
Dairy manure subjected to four pretreatments (acid, alkaline, sulfite (SPORL), alkaline hydrogen peroxide (AHP)) at high chemical dosages (termed severe conditions) were evaluated for enhancements in biogas production and inhibitory effects due to concomitant generation of furan byproducts. All four pretreatments enhanced solubilization of carbohydrates, but only alkaline and AHP resulted in higher methane yield (356 and 333 mL/g-VS, respectively) relative to moderate pretreatment conditions (311 and 261 mL/g-VS, respectively). Methane yield of severe-SPORL pretreatment (233 mL/g-VS) was greater than that of untreated manure (116 mL/g-VS), but lower than that of moderate-SPORL (353 mL/g-VS). Severe-acid pretreatment showed early termination in biogas production likely due to inhibitory effects of furfural and 5-hydroxymethyl furfural. Both experimental data and kinetic modeling indicated that severe-acid pretreatment led to degradation of carbohydrates to furfural, which reduced biogas production due to direct toxicity rather than competitive inhibitory effects. Pretreatment conditions (severity and byproduct levels) for dairy manure biomass may be optimized based on the current findings.
Assuntos
Lignina , Esterco , Anaerobiose , Biocombustíveis , Lignina/metabolismo , MetanoRESUMO
Developing low-cost and high-performance biosorbent for water purification continues drawing more and more attention. In this study, cellulose-chitosan composite hydrogels were fabricated via a co-dissolution and regeneration process using a molten salt hydrate (a 60 wt% aqueous solution of LiBr) as a solvent. The addition of chitosan not only introduced functionality for metal adsorption but also increased the specific surface area and improved the mechanical strength of the composite hydrogel, compared to pure cellulose hydrogel. Batch adsorption experiments indicated that the composite hydrogel with 37% cellulose and 63% chitosan exhibited an adsorption capacity of 94.3 mg/g (1.49 mmol/g) toward Cu2+ at 23 °C, pH 5, and initial metal concentration of 1500 mg/L, which was 10 times greater than the adsorption capacity of pure cellulose hydrogel. Competitive adsorption from a mixed metals solution revealed that the cellulose-chitosan composite hydrogel exhibited selective adsorption of the metals in the order of Cu2+ > Zn2+ > Co2+. This study successfully demonstrated an innovative method to fabricate biosorbents from abundant and renewable natural polymers (cellulose and chitosan) for removing metal ions from water.
Assuntos
Quitosana , Metais Pesados , Poluentes Químicos da Água , Purificação da Água , Adsorção , Celulose , Hidrogéis , Concentração de Íons de Hidrogênio , Cinética , Solubilidade , Poluentes Químicos da Água/análiseRESUMO
Monodispersed colloidal gold nanoparticles (AuNPs) were synthesized by an easy, cost-effective, and eco-friendly method. The AuNPs were mostly quasi-hexagonal in shape with sizes ranging from 15 to 18 nm. A screen-printed electrode modified with AuNPs (AuNPs/SPE) was used as an electrochemical sensor for the detection of As(iii) in water samples. The mechanistic details for the detection of As(iii) were investigated and an electrochemical reaction mechanism was proposed. Under the optimal experimental conditions, the sensor was highly sensitive to As(iii), with a limit of detection of 0.11 µg L-1 (1.51 nM), which is well below the regulatory limit of 10 µg L-1 established by the United States Environmental Protection Agency and the World Health Organization. The sensor responses were highly stable, reproducible, and linear over the As(iii) concentration range of 0.075 to 30 µg L-1. The presence of co-existing heavy metal cations such as lead, copper, and mercury did not interfere with the sensor response to As(iii). Furthermore, the voltammogram peaks for As(iii), lead, copper, and mercury were sufficiently separate for their potential simultaneous measurement, and at very harsh acidic pH it may be possible to detect As(v). The AuNPs/SPE could detect As(iii) in tap water samples at near-neutral pH, presenting potential possibilities for real-time, practical applications.
RESUMO
Reducing agricultural runoff is important year round, particularly on landscapes that receive wintertime applications of manure. No-tillage systems are typically associated with reduced runoff loads during the growing season, but surface roughness from fall tillage may aid infiltration on frozen soils by providing surface depressional storage. The timing of winter manure applications may also affect runoff, depending on snow and soil frost conditions. Therefore, the objective of this study was to evaluate runoff and nutrient loads during the freezing season from combinations of tillage and manure application timings. Six management treatments were tested in south-central Wisconsin during the winters of 2015-2016 and 2016-2017 with a complete factorial design: two tillage treatments (fall chisel plow vs. no-tillage) and three manure application timings (early December, late January, and unmanured). Nutrient loads from winter manure application were lower on chisel-plowed versus untilled soils during both monitoring years. Loads were also lower from manure applied to soils with less frost development. Wintertime manure applications pose a risk of surface nutrient losses, but fall tillage and timing applications to thawed soils can help reduce loads.
Assuntos
Esterco , Nutrientes , Agricultura , Congelamento , Fósforo , Estações do Ano , Solo , WisconsinRESUMO
Agricultural P loss from fields is an issue due to water quality degradation. Better information is needed on the P loss in runoff from dairy manure applied in winter and the ability to reliably simulate P loss by computer models. We monitored P in runoff during two winters from chisel-tilled and no-till field plots that had liquid dairy manure applied in December or January. Runoff total P was dominated by nondissolved forms when soils were bare and unfrozen. Runoff from snow-covered, frozen soils had much less sediment and sediment-related P, and much more dissolved P. Transport of manure solids was greatest when manure was applied on top of snow and runoff shortly after application was caused by snowmelt. Dissolved P concentrations in runoff were greater when manure was applied on top of snow because manure liquid remained in the snowpack and allowed more P to be available for loss. Dissolved runoff P also increased as the amount of rain or snowmelt that became runoff (runoff ratio) increased. The SurPhos manure P runoff model reliably simulated these processes to provide realistic predictions of dissolved P in runoff from surface manure. Overall, for liquid dairy manure applied in winter, dissolved P concentrations in runoff can be decreased if manure is applied onto bare, unfrozen soil, or if runoff ratio can be reduced, perhaps through greater soil surface roughness from fall tillage. Both management approaches will allow more manure P to infiltrate into soil and less move in runoff. SurPhos is a tool that can reliably evaluate P loss for different management and policy scenarios for winter manure application.
Assuntos
Esterco , Fósforo , Agricultura , Chuva , Solo , Movimentos da ÁguaRESUMO
The effect of anaerobic digestion on phosphorus (P) forms and water P extractability was investigated using dairy manure samples from six full-scale on-farm anaerobic digesters in Wisconsin, USA. On an average, total dissolved P (TDP) constituted 12 +/- 4% of total P (TP) in the influent to the anaerobic digesters. Only 7 +/- 2% of the effluent was in a dissolved form. Dissolved unreactive P (DUP), comprising polyphosphates and organic P, dominated the dissolved P component in both the influent and effluent. In most cases, it appeared that the fraction of DUP mineralized during anaerobic digestion became subsequently associated with particulate-bound solids. Geochemical equilibrium modeling with Mineql+ indicated that dicalcium phosphate dihydrate, dicalcium phosphate anhydrous, octacalcium phosphate, newberyite, and struvite were the probable solid phases in both the digester influent and effluent samples. The water-extractable P (WEP) fraction in undigested manure ranged from 45% to 70% of TP, which reduced substantially after anaerobic digestion to 25% to 45% of TP. Anaerobic digestion of dairy manure appears capable of reducing the fraction of P that is immediately available by increasing the stability of the solid phases controlling P solubility.
Assuntos
Esterco/análise , Fósforo/isolamento & purificação , Fósforo/metabolismo , Anaerobiose , Ração Animal , Animais , Bovinos , Indústria de Laticínios , Termodinâmica , WisconsinRESUMO
Humic substances, by altering the surface properties and/or competing for available reaction sites, can either suppress or promote sorption of organic compounds to mineral surfaces. Limited literature evidence points to the reduction in sorption of the antibiotic tetracycline to clay minerals in the presence of humic substances. We investigated the surface interaction of Elliott soil humic acid (ESHA) with hydrous Al oxide (HAO) and the effect of this association on tetracycline sorption. Strong interaction between ESHA and HAO led to ESHA-promoted dissolution of HAO and surface charge reversal. The ESHA-HAO sorption-desorption isotherms were successfully described using a modified Langmuir model that accounted for the heterogeneity of HAO surface and ESHA. Ligand exchange was proposed as the major interaction mechanism, and the edge Al atoms on HAO surface were considered as the sorption sites for ESHA macromolecules. ESHA was coated onto HAO to achieve two different organic content (foc) levels of 0.81 and 1.52%. Sorption results were compared for the binary ESHA-tetracycline and HAO-tetracycline systems, and the ternary ESHA-HAO-tetracycline system. The coating of ESHA on HAO significantly suppressed tetracycline sorption levels, attributable to altered HAO surface charge characteristics and/or direct competition between ESHA and tetracycline for potential sorption sites. Higher foc level, besides increasing the extent of sorption suppression, also resulted in greater ionic strength dependence and increased nonlinearity of sorption behavior. It, therefore, appears that the presence of humic substances, in both dissolved and mineral-bound forms, is likely to increase the environmental mobility of tetracycline compounds.
Assuntos
Óxido de Alumínio/química , Antibacterianos/química , Substâncias Húmicas , Poluentes do Solo/química , Tetraciclina/química , Adsorção , Concentração de Íons de HidrogênioRESUMO
Meeting stringent phosphorus (P) discharge standards remains one of the major challenges for wastewater utilities due to increased economic burdens associated with advanced (i.e., secondary, tertiary) treatment processes. In a trade-off between higher treatment cost and enhanced P removal, it is critical for the treatment plants to be able to select the most appropriate technology. To this end, established/emerging high performing P removal/recovery technologies (e.g., Modified University of Cape Towne process, Bardenpho process, membrane bioreactors, IFAS-EBPR, struvite recovery, tertiary reactive media filtration) were identified and full-scale treatment plant designs were developed. Using advanced mathematical modeling techniques, six different treatment configurations were evaluated in terms of performance and cost effectiveness ($/lb of P removed). Results show that the unit cost for P removal in different treatment alternatives range from $42.22 to $60.88 per lb of P removed. The MUCT BNR + tertiary reactive media filtration proved to be one of the most cost effective configurations ($44.04/lb P removed) delivering an effluent with total P (TP) concentration of only 0.05 mg/L. Although struvite recovery resulted in significant reduction in biosolids P, the decrease in effluent TP was not sufficient to meet very stringent discharge standards.
Assuntos
Reatores Biológicos/economia , Análise Custo-Benefício/estatística & dados numéricos , Filtração/economia , Fósforo/química , Águas Residuárias/química , Purificação da Água/economia , Filtração/métodos , Modelos Teóricos , Nitrogênio , Estruvita/química , Eliminação de Resíduos Líquidos/métodos , Purificação da Água/métodosRESUMO
In this study the capacity of sorbents prepared from juniper wood (JW) and bark (JB) to adsorb cadmium (Cd) from aqueous solutions at different pH values was compared. Adsorption behavior was characterized through adsorption kinetics, adsorption isotherms, and adsorption edge experiments. Results from kinetics and isotherm experiments showed that JB (76.3-91.6 micromol Cdg(-1) substrate) had 3-4 times higher adsorption capacity for Cd than JW (24.8-28.3 micromol Cdg(-1)). In addition to higher capacity, JB exhibited a higher strength of adsorption (45.3 versus 9.1 Lmmol(-1)) and faster uptake kinetics (0.0119 versus 0.0083 g micromol(-1)min(-1)) compared to JW. For both these adsorbents, increasing Cd adsorption with increasing solution pH in the range of 2-6 suggests that surface carboxyl groups (RCOOH) might be involved in interaction with Cd. Diffuse reflectance infrared Fourier transform (DRIFT) spectra showed that the surface concentration of carboxyl groups was higher on JB compared to JW. The ratio of Ca released to Cd adsorbed was 1.04 and 0.78 for JB and JW, respectively, indicating that Ca-Cd ion-exchange was the primary mechanism involved. The higher Ca content in JB (15 times more) and the surface RCOOH concentration (2.5 times more) can be attributed to the observed differences in Cd adsorption behavior between the two lignocellulosic adsorbents.
Assuntos
Cádmio/química , Juniperus/química , Casca de Planta/química , Madeira/química , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Fatores de Tempo , Poluentes Químicos da Água/químicaRESUMO
The effect of solution chemistry and sorbate-to-sorbent ratio on the interaction of the antibiotic tetracycline with Elliott soil humic acid (ESHA) was investigated using equilibrium dialysis and FITEQL modeling. Tetracycline speciation strongly influenced its sorption to ESHA. Sorption was strongly pH-dependent with a maximum around pH 4.3, and competition with H+ and electrolyte cation (Na+) was evident. The pH-dependent trend was consistent with complexation between the cationic/zwitterionic tetracycline species and deprotonated sites in ESHA (mainly carboxylic functional groups). Modification of ESHA by Ca2+ addition increased tetracycline sorption suggesting that ternary complex formation (ESHA-metal-tetracycline) may be important at higher concentrations of multivalent metal cations. The macroscopic data (pH-envelope and sorption isotherms) were successfully modeled using a discrete logK function with the FITEQL 4.0 chemical equilibrium program indicating that ESHA-tetracycline interaction could be reasonably represented as complex formation of a monoacid with discrete sites in humic acid. Sorption-desorption hysteresis was observed; both sorption and desorption isotherms were well described by the Freundlich equation.
Assuntos
Substâncias Húmicas/análise , Tetraciclina/análise , Adsorção , Concentração de Íons de Hidrogênio , Modelos Químicos , Solo/análise , Tetraciclina/química , TermodinâmicaRESUMO
Intensive manure application is an important source of diffuse phosphorus (P) pollution. Phosphorus availability from animal manure is influenced by its chemical speciation. The major objective of this study was to investigate the P speciation in raw and anaerobically digested dairy manure with an emphasis on the calcium (Ca) and magnesium (Mg) phosphate phases. Influent and effluent from an on-farm digester in Wisconsin were sampled and sieved, and the 25 to 53 microm size fraction was dried for X-ray powder diffraction (XRD) and P K-edge X-ray absorption near edge structure (XANES) analyses. Struvite (MgNH4PO4.6H2O) was identified in both the raw (influent) and anaerobically digested (effluent) manure using XRD. Qualitative analysis of P K-edge XANES spectra indicated that the Ca orthophosphate phases, except dicalcium phosphate anhydrous (DCPA) or monetite (CaHPO4), were not abundant in dairy manure. Linear combination fitting (LCF) of the P standard compounds showed that 57.0 and 43.0% of P was associated with DCPA and struvite, respectively, in the raw manure. In the anaerobically digested sample, 78.2% of P was present as struvite and 21.8% of P was associated with hydroxylapatite (HAp). The P speciation shifted toward Mg orthophosphates and least soluble Ca orthophosphates following anaerobic digestion. Similarity between the aqueous orthophosphate (aq-PO4), newberyite (MgHPO4.3H2O), and struvite spectra can cause inaccurate P speciation determination when dairy manure is analyzed solely using P K-edge XANES spectroscopy; however, XANES can be used in conjunction with XRD to quantify the distribution of inorganic P species in animal manure.
Assuntos
Indústria de Laticínios , Esterco/análise , Fósforo/análise , Análise Espectral/métodos , Raios X , Anaerobiose , ProbabilidadeRESUMO
Samples from several wastewater treatment facilities in Wisconsin were screened for the presence of 21 antibiotic compounds. These facilities spanned a range of community size served (average daily flow from 0.0212 to 23.6 million gallons/day), secondary treatment processes, geographic locations across the state, and they discharged the treated effluents to both surface and ground waters (for ground water after a soil passage). A total of six antibiotic compounds were detected (1-5 compounds per site), including two sulfonamides (sulfamethazine, sulfamethoxazole), one tetracycline (tetracycline), fluoroquinolone (ciprofloxacin), macrolide (erythromycin-H(2)O) and trimethoprim. The frequency of detection of antibiotics was in the following order: tetracycline and trimethoprim (80%)>sulfamethoxazole (70%)>erythromycin-H(2)O (45%)>ciprofloxacin (40%)>sulfamethazine (10%). However, the soluble concentrations were in the parts-per-billion (ppb) range (Assuntos
Antibacterianos/análise
, Eliminação de Resíduos Líquidos
, Poluentes Químicos da Água/análise
, Monitoramento Ambiental
, Abastecimento de Água/análise
, Wisconsin
RESUMO
This work describes a simple, passive sampling system for measuring runoff, sediment, and chemical losses from typical agricultural fields. The sampler consists of a 5 to 7 m wide runoff collector connected to a series of multislot divisors. These divisors split the flow into aliquots, providing a continuous sampling during the runoff event. Divisors were located in a wooden box below ground level. With an adequate pump, this system can operate in fields with a slope gradient as low as 2%, and can stay in the field during winter to record first snowmelt-generated runoff. A radio transmitter reports by telemetry the occurrence and magnitude of any runoff event, and indicates when the system should be sampled and emptied. This article includes a description of the equipment, advantages, and disadvantages based on 2 yr of operation, and examples of data collected.
Assuntos
Agricultura , Sedimentos Geológicos , Água , Armazenamento e Recuperação da InformaçãoRESUMO
There is growing interest in evaluating the effects of corn silage harvesting methods on erosion control. Increasing the silage cutting height will increase residue cover and could conceivably minimize off-site migration of sediments compared with conventional silage harvesting. The effects of residue level and manure application timing on runoff and sediment losses from no-till corn were examined. Treatments included conventional corn grain (G) and silage (SL) and nonconventional, high-cut (60-65 cm) silage (SH). Corn harvesting treatments were subjected to different manure application regimes: no manure (N) or surface application in fall (F) or spring (S). Simulated rainfall (76 mm/h; 1 h) was applied in spring and fall for two years (2002-2003), runoff from 2.0- x 1.5-m plots collected, and a subsample analyzed for sediment concentration and aggregate size distribution. Runoff volume was inversely related to residue cover. Manure addition to silage plots reduced spring runoff by 71 to 88%, attributable to an increase in soil organic matter content, compared with SH-N and SL-N. Differences in sediment concentration between SH and SL were not significant. For silage plots, spring-applied manure had the greatest influence on sediment export reducing it by 84 to 93% in spring runoff compared with corresponding N plots. Sediment loads were also 85 to 97% lower from SH-S compared with SL-N in all four seasons. Except for spring 2003, sediment export was lower from G compared with SL. The combination of manure and higher residue associated with high-cut silage often lowered sediment export compared with low-cut silage. Nearly identical aggregate size distributions were observed in sediments from SH and SL plots. High residue levels combined with spring-applied manure led to enrichment in the clay-sized fraction of runoff sediment. Recently applied manure and higher residue levels achieved by high-cutting silage can substantially lower sediment losses in spring runoff when soil is most susceptible to erosion.