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The elemental composition of soil plays an essential role in crop nutrition, but losses from croplands can negatively impact soil fertility and water quality. We compared the impact of strip tillage (ST) and conventional tillage (CT) on element concentrations and loads in surface runoff and subsurface flow from plots under rotational cotton (Gossypium hirsutum L.) and peanut (Arachis hypogaea L.) production with winter cover cropping. Total element concentrations (calcium [Ca], iron [Fe], potassium [K], magnesium [Mg], manganese [Mn], sodium [Na], phosphorus [P], sulfur [S], silicon [Si], and zinc [Zn]) in surface runoff and subsurface flow samples were measured using Inductively Coupled Plasma with Optical Emission Spectroscopy (ICP-OES). Element loads were estimated by multiplying the element concentrations by the surface runoff and drainage volumes. Significantly greater (p ≤ 0.05) surface runoff loads for all elements (with the exception of K and Zn) were observed from the CT compared with the ST treatment plots only in 2006, likely due to the combined effects of hydrology and the timing of gypsum amendments that year. Surface runoff was the primary hydrologic pathway for Fe, K, Mn, P, Si, and Zn loss while subsurface flow was the primary hydrologic pathway for Ca, Mg, and S loss with both tillage treatments. Lower concentrations of Ca, Mg, Na, and S in the subsurface flow with ST compared to CT suggest that this tillage practice, in conjunction with the proper timing of fertilizer and soil amendment applications (e.g., poultry litter and gypsum) can be an effective method for reducing element losses from croplands. This finding highlights the importance of conservation practices in sustaining healthy cropland soils while reducing element losses and associated environmental impacts.

Global carbon (C) and nitrogen (N) cycles are closely linked to erosion and hydrologic processes. By reducing tillage erosion and runoff, sediment-bound C and N losses can be reduced. Published studies represent only a few soil types and regions and rarely directly compare tillage practices. The objective of this study was to quantify concentrations and sediment-bound total organic carbon (TOC) and nitrogen (TON) loads and enrichment ratios in runoff from 0.2-ha fields in rotational cotton (Gossypium hirsutum L.)-peanut (Arachis hypogea L.) production during a 7-yr study within a southeastern USA coastal plain landscape. The Ultisoils at the study site have loamy sand to sandy loam texture surface horizons. The fields were in either continuous conventional tillage (CT) or strip tillage (ST) and were at upper, middle, and lower landscape positions. Sediment-bound TON and TOC concentrations were significantly greater from ST than CT fields as were the TOC and TON enrichment ratios. However, due to greater surface runoff and sediment loss, TON and TOC loads were significantly greater from CT than ST fields. The CT and ST loads were significantly different at the upper and middle but not at the lower landscape position. Enrichment ratios, 14 to 19 for TON and 8 to 12 for TOC, were several-fold greater than reported in the limited available literature, where studies focused on finer textured surface soils. Our findings have highlighted the site-specific nature of erosion processes, how they affect sediment-bound C and N loss in agricultural landscapes, and how reducing tillage may impact sediment C and N dynamics. The observed enrichment ratios can be used to modify or adjust values used in current erosion models and improve their suitability for use in the region and elsewhere where surface soils have sandy texture and when practices like ST are implemented.

Conservation tillage (CsT) involves management that reduces soil erosion by maintaining crop residue cover on farm fields. Typically, both infiltration and soil organic matter increase over time with CsT practices. We compared the impact of a commonly used CsT practice, strip tillage (ST), to conventional tillage (CT) management on soil nitrogen (N) dynamics and leaching and examined associations to soil N availability and microbial biomass. A winter cover crop was used in both tillage treatments. The study was conducted over a five-year period during rotational cotton (Gossypium hirsutum L.) and peanut (Arachis hypogaea L.) production in the Atlantic Coastal Plain region in Georgia, United States. Fertilizer and poultry litter were applied ahead of the cotton crops. Sets of PVC cylinders were filled with soil from each of six plots, three in ST and three in CT, and maintained in situ in their respective plots for 16 intervals of about 90 days. After retrieval, the soil in each cylinder was analyzed for inorganic N (ammonium and nitrates [NH4+ and NO3−]), total N, total carbon (C), and microbial biomass. Leached NO3−-N was captured on anion exchange resin-filled bags attached to the bottom of each cylinder. After the five-year study period, the ST and CT soil C content increased by 22% and 23%, respectively. Total soil N content increased 27% with ST compared to 22% with CT. Temporal patterns in NO3−-N leaching were not different between CT and ST treatments, and a high amount of NO3−-N leaching was observed after the application of poultry litter. The cumulative amount of NO3−-N leached from soils throughout the five-year study was 141 and 122 kg N ha−1 (126 and 109 lb N ac−1) with CT and ST practices, respectively. Results suggest that leaching from the top 15 cm (6 in) of soil may be an important pathway of N loss from both CT and ST cropping systems in the region. Regardless of tillage, soil microbial biomass N was equal to or higher than the total inorganic N, but still represented a small percentage (up to 9%) of the total soil N. Overall, microbial biomass N was higher in ST compared to CT. Minimizing NO3−-N in the soil from reaching ground and surface waters while increasing crop productivity represents a major challenge. The use of ST in conjunction with winter cover crops may improve plant N availability by more than 27 kg ha−1 y−1 (24 lb ac−1 yr−1) in the sandy landscapes of the southeastern Coastal Plain region through microbial cycling of organic N while reducing subsurface NO3−-N losses.

To control weeds with evolved resistance to glyphosate, Southeastern (USA) cotton farmers have increased fomesafen (5-(2-chloro-α,α,α-trifluoro-p-tolyloxy)-N-mesyl-2-nitrobenzamide) use. To refine fomesafen risk assessments, data are needed that describe its dissipation following application to farm fields. In our study, relatively low runoff rates and transport by lateral subsurface flow,1.0 and 0.15% of applied respectively, were observed. The low runoff rate was linked to postapplication irrigation incorporation and implementation of a common conservation tillage practice. Moderate soil persistence (t1/2 = 100 days) was indicated in laboratory incubations with surface soil, however, analysis of soil cores from treated plots showed that ≈3% of fomesafen applied persisted in subsoil3 years after application. Findings suggest low potential for fomesafen movement from treated fields, however, the fate of fomesafen that accumulated in subsoil and the identity of degradates are uncertain. Soil and water samples were screened for degradates, but, none were detected.

Agrichemical runoff from farmland may adversely impact coastal water quality. Two models, the Agricultural Policy/Environmental eXtender (APEX) and the Riparian Ecosystem Management Model (REMM), were used to evaluate the movement of the herbicide atrazine to the Jobos Bay National Estuarine Research Reserve from adjacent fields. The reserve is located on Puerto Rico’s southeast coast. Edge-of-field atrazine outputs simulated with the APEX were routed through a grass-forest buffer using the REMM. Atrazine DT50 (half-life) values measured in both field and buffer soils indicated that accelerated degradation conditions had developed in the field soil due to repeated atrazine application. APEX simulations examined both the measured field and buffer soil atrazine DT50 and the model’s default value. The use of the measured field soil atrazine degradation rate in the APEX resulted in 33 % lower atrazine transport from the field. REMM simulations indicated that the buffer system had the potential to reduce dissolved atrazine transport in surface runoff by 77 % during non-tropical storm events by increasing infiltration, slowing transport, and increasing time for pesticide degradation. During a large runoff event due to a tropical storm that occurred close to the time of an atrazine application, the REMM simulated only a 37 % reduction in atrazine transport. The results indicate that large storm events soon after herbicide application likely dominate herbicide transport to coastal waters in the region. These results agree with water quality measurements in the reserve. This study demonstrated the sensitivity of these models to variations in DT50 values in evaluating atrazine fate and transport in the region and emphasizes that the use of measured DT50 values can improve model accuracy.

The seed oil content of 305 genebank accessions of eggplant (Solanum melongena), five related species (S. aethiopicum L., S. incanum L., S. anguivi Lam., S. linnaeanum Hepper and P.M.L. Jaeger and S. macrocarpon L.) and 27 additional Solanums pecies, was determined by NMR. Eggplant (S. melongena) seed oil content varied from 17.2% (PI 63911317471) to 28.0% (GRIF 13962) with a mean of 23.7% (std. dev = 2.1) across the 305 samples. Seed oil content in other Solanum species varied from 11.8% (S. capsicoides-PI 370043) to 44.9% (S. aviculare-PI 420414). Fatty acids were also determined by HPLC in genebank accessions of S. melongena (55), S. aethiopicum (10), S. anguivi (4), S. incanum (4) and S. macrocarpon (2). In all samples examined, the predominant fatty acid was linoleic acid (18:2) followed by oleic acid (18:1) and palmitic acid (16:0). Levels of linoleic acid ranged from 57% (S. aethiopicum-PI 194166) to 74.5% (S. anguivi-PI 183357). Oleic and palmitic acid levels ranged from 11.3% (S. anguivi-PI 183357) to 25.2% (S. aethiopicum-PI 194166) and 8.4% (S. melongena-PI 115507) to 11.2% (S. melongena-PI 600912), respectively. Oil extracted from seed of S. melongena cv. Black Beauty had a pour point of -12°C, viscosities of 28.8 (40°C) and 7.3 (100°C), a viscosity index of 240, an oxidation onset temperature of 160°C and a Gardner Color of 6+.

Losses of soluble nutrients from cropland and their transport to surface and groundwater are a continuing water quality concern. In this study, we evaluated tillage impacts on dissolved losses of ammonium (NH4-N), nitrate nitrogen (NO3-N), chloride (Cl), and potassium (K) during rotational cotton and peanut production. Tillage treatments were strip tillage (ST), in which crops were planted into 15 cm strips tilled into cover crop residue mulch, and conventional tillage (CT), in which all crop residues were turned into the soil prior to planting. Winter cover crops were used in both tillage systems. Tillage and irrigation treatments were uniformly applied within two 0.6 ha fields located on a moderately sloping hillslope in the southern Atlantic Coastal Plain region of south-central Georgia. Tile drains were installed at the base of the slope of each field to capture and measure lateral subsurface flow. Each field was subdivided into three 0.2 ha plots, with the three plots making up a single tillage block. H-flumes were used for flow measurement and sample collection. During the five-year study, annual precipitation ranged from 910 to 1488 mm, with an annual average of 1201 mm. Annual surface runoff averaged 17% of annual rainfall from the CT field and 11% from the ST field. Because of relatively low variability in concentrations, surface runoff loads closely tracked surface runoff volumes. Annual surface runoff loadings of NH4-N, NO3-N, and Cl from the ST treatment were found to be significantly less than those from the CT treatment. The total five-year load of N (NH4-N and NO3-N) in surface runoff from CT was 8.3 kg ha-1, while it was 5.6 kg ha-1 from ST, equivalent to 1.5% of the total N applied to CT and 1.0% of that applied to ST. Annual subsurface flow averaged 12% of annual precipitation for CT and 21% for ST. Annual average subsurface flow loadings of NH4-N, NO3-N, and K from ST were significantly greater than from CT. The total five-year load of N (NH4-N and NO3-N) in subsurface flow was 45 kg ha-1 from CT and 99 kg ha-1 from ST, equivalent to 8.3% and 18.4% of the total N applied to CT and ST, respectively. Data showed that subsurface flow was the primary hydrologic pathway for dissolved N and Cl loss in both tillage systems. Overall, ST was found to be an effective method for reducing surface runoff and associated soluble losses, but increased infiltration with this practice significantly increased subsurface losses. This introduces a challenge to nitrogen management in reduced tillage systems such as ST in the region.

Helicoverpa zea (Boddie) is a major insect pest of corn and other agricultural crops. An improved understanding of semiochemcials that control adult behavior is needed to develop alternative control measures. In this study, overnight SPME collection of volatiles from corn ears enclosed in Teflon bags in the field at two stages of development were made. C8–C10 aldehydes, a C8-alcohol, C6–C9 alcohol acetates, and numerous monoterpenes, sesquiterpenes, sequiterpene alcohols, and geosmin were identified after thermal desorption and GC/MS. Structural assignments of the alcohol acetates, Z-3-hexenyl acetate, 2-heptyl acetate, 2-nonyl acetate, and 4-nonyl acetate, the monoterpenes, α- and β-ocimene, and geosmin were made by analysis of standards that were purchased or prepared in the laboratory. All other assignments were based on published Kovat’s retention time indices (KI) and mass spectra. Pair-wise comparison of the relative amounts of each component between two groups of corn ears defined by silk weight did not identify significant differences, thus it is unknown whether or not silk weight impacted volatile emission composition and rate. To our knowledge three compounds detected in SPME collections, 2-heptyl acetate, 2-nonyl acetate, and 4-nonyl acetate have not been previously reported in corn ear or silk volatiles. Their impact on the flight response of gravid earworm females was evaluated in a flight chamber. No significant response to the individual compounds or a blend of all three was observed. Thus, their impact on moth behavior remains uncertain.

Biochars were produced by pyrolysis of sugarcane bagasse (350 °C and 700 °C) and pine wood (400 °C) and are abbreviated BC350, BC700, and WC400, respectively. Metribuzin adsorption by batch equilibrium showed that BC700 had the greatest adsorption capacity followed by BC350 and WC400. The bagasse biochars were mixed with clay and a silt loam soil and the pine wood biochar with a loamy sand soil and fortified with the metribuzin and pendimethalin. The soils were incubated at 25 °C in the dark and were extracted with methanol after 0, 7, 14, 21, 28, 42, 63, 86, and 111 days. Parent compounds and metribuzin degradates were analyzed in extracts by HPLC – mass spectrometry. Increases in metribuzin half life (DT50) were indicated for all soil-biochar combinations. BC350 had the greatest impact, doubling the DT50 in the silt loam soil. In contrast, BC700 had minimal impact on the DT50 in the silt loam soil and contributed to a significant DT50 decrease in the clay. The metribuzin degradate, metribuzin-desamino, was detected at rates proportional to metribuzin dissipation. For pendimethalin, biochar additions increased DT50 in all soil-biochar combinations. In contrast to metribuzin, BC700 and WC400 had the greatest impact with the BC700 increasing the DT50 more than 2-fold. In the loamy sand soil, the 1–4% biochar rate contributed to an increased trend in palmer amaranth emergence. At the 8% rate, palmer amaranth emergence was statistically higher than the control (p = 0.072). In sum, how biochar impacted the activity and dissipation of these herbicides depended on soil, herbicide, and biochar properties.

There is worldwide interest in conservation tillage practices because they can reduce surface runoff, and agrichemical and sediment losses from farm fields. Since these practices typically increase infiltration, their use may increase subsurface transport of water-soluble contaminants. Thus, to assess long-term environmental benefits of conservation tillage data may be needed that quantify both surface and subsurface contaminant fluxes. This study focused on the herbicide fluometuron (N,N-dimethyl-N′-[3-(trifluoromethyl)phenyl]-urea) and its soil degradate DMF (N-methyl-N′-[3-(trifluoromethyl) phenyl]-urea). Both compounds are classed as “leachable”. They were measured for 10 years in surface runoff and lateral subsurface flow from paired fields located on a hill slope in the Atlantic Coastal Plain region of the southeastern USA. One group of fields was conventionally tilled incorporating all crop residues into soil prior to planting. The second was strip tilled, a common conservation tillage practice. Seven fluometuron applications were made to cotton ( Gossypium hirsutum ) produced in rotation with peanut ( Arachis hypogea ). Combined fluometuron and DMF surface and subsurface losses from the conventionally tilled fields were equivalent to 1.2% and 0.13% of fluometuron applied and 0.31% and 0.32% from the strip tilled fields. Annual surface runoff losses were significantly greater from the conventionally tilled fields while the strip tilled fields had significantly greater annual subsurface losses. Results demonstrated that shifting from conventional to conservation tillage management of farm fields in this landscape will reduce surface runoff losses of herbicides like fluometuron but subsurface losses will likely increase. The same trends can be expected in landscapes with similar soil and hydrologic properties. This should be considered when planning implementation of programs that promote conservation tillage use.

Widespread implementation of conservation tillage systems during cotton (Gossypium hirsutum L.) and pea- nut (Arachis hypogea L.) production in the Atlantic Coastal Plain region of the U.S. has substantially reduced erosion and sediment loss. However, the benefits of conservation tillage in these cropping systems are being threatened by weather shifts that include increased frequency of high-intensity rainfall, policies that encourage the removal of crop residues as cellulosic feedstocks for energy production, and increased herbicide resistance in weeds. Long-term integrated studies are needed to quantify potential impacts. We evaluated runoff and sediment loss from six 0.2 ha fields located on a gently sloping hillslope in a Southern Atlantic Coastal Plain landscape over ten years (2000-2009) during rotational cotton- peanut production, with a rye (Secale cereale) winter cover crop. Half of the fields were in conventional tillage (CT; in- version tillage with cover crop residue incorporation prior to planting), and half were in strip tillage (ST), which is a commonly used conservation tillage practice in the region. Fields were laid out as contrasting tillage pairs at upper, mid- dle, and lower landscape positions and irrigated as needed. Runoff and sediment load from CT fields was significantly greater than from ST fields at each landscape position. Over the 10-year study period, mean annual total sediment load was 1823 kg ha -1 year -1 from CT fields and 237 kg ha -1 year -1 from ST fields (an 87% difference), and runoff was reduced by 41%. A soil tolerance value (T) of 2,200 kg ha -1 year -1 was exceeded in three out of ten years in CT fields and never exceeded in ST fields. On a monthly basis, extreme events (>90th percentile; 10%) accounted for 61% to 72% of the 10- year total sediment load for the CT system (341 to 2,828 kg ha -1 month -1 ) and 73% to 84% for the ST system (49 to 593 kg ha -1 month -1 ). The rainfall and irrigation total was above the normal monthly rainfall in 83% of these extreme monthly periods (mean 179 mm, range 81 to 316 mm). Sediment load was greatest in summer and spring, and during cotton pro- duction. The study results improve estimates of the increase in rainfall event size tolerated by CT vs. ST cropping systems, demonstrate the benefits of conservation tillage management during cotton and peanut production, and are expected to guide management decisions that focus on reducing sediment loss in this landscape. Specifically, the results point to the use of cover crops and strip tillage as essential best management practices for this purpose.

Peanut (Arachis hypogaea) is produced intensively in the southern Atlantic Coastal Plain of the eastern USA. To effectively protect the region's water quality data are needed which quantify runoff of pesticides used to protect these crops. Fungicides are used intensively yet there is little published data which describe their potential for loss in surface runoff. This study compared runoff of a fungicide, tebuconazole (α-[2-(4-chlorophenyl)ethyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol), and an herbicide, metolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide) from 0.2 ha fields in strip (ST), a commonly used conservation-tillage practice, and conventional tillage (CT) near Tifton, GA (USA). Following their first application, metolachlor and tebuconazole were detected at high frequency in runoff. Concentrations and their annual losses increased with application frequency and runoff event timing and frequency with respect to applications, and when fields were positioned at the top of the slope and CT was practiced. Runoff one day after treatment (DAT) contributed to high tebuconazole runoff loss, up to 9.8% of the amount applied on an annual basis. In all cases, metolachlor loss was more than 10 times less even though total application was 45% higher. This was linked to the fact that the one metolachlor application to each crop was in May, one of the region's driest months. In sum, studies showed that fungicide runoff rates may be relatively high and emphasize the need to focus on these products in future studies on peanut and other crops. The study also showed that peanut farmers should be encouraged to use conservation tillage practices like ST which can substantially reduce pesticide runoff.

Growing populations and food demand in the tropics are leading to increased environmental pressures on wetland ecosystems, including a greater reliance on natural wetlands for water quality improvement. Effective assessment of wetland treatment potential requires an improved understanding of the hydraulic and biogeochemical factors that govern contaminant behavior, however detailed studies of flow through natural, tropical wetlands are scarce. We performed a tracer study using a conservative salt (potassium bromide) to examine the hydraulic behavior of a small, natural wetland in the Costa Rican humid tropics and modeled observed breakthrough curves using the 1-D advection–dispersion equation. Velocities in the wetland were extremely slow, from less than 4 m day−1 to a maximum of ~30 m day−1, and were distributed across several flowpaths, illustrating a spatial heterogeneity of flow and velocities. Modeled dispersion coefficients were also low (33 ± 33 m2 day−1). Estimated residence times suggested high potential pollutant removal capacity over a range of influent concentrations, reinforcing the environmental services provided by this and other small tropical wetlands. The study also highlighted how small variations in wetland topography and vegetation yield strong differences in transport patterns that affect transport and mixing in densely vegetated, heterogeneous wetland systems. Empirical data on the hydraulics, and resulting ecosystem functions, of small, distributed wetlands may provide support for improved conservation and management of these important ecosystems.

Georgia farmers are increasing preemergence applications of soil residual herbicides to control glyphosate resistant weeds. To improve efficacy these herbicides are often activated by post-application irrigation. Broiler litter is commonly applied to fields before these herbicides. The herbicide wetting-in practice increases surface soil water content and may increase runoff and transport of broiler litter borne fecal bacteria into surface waters during subsequent storm events. Our objective was to determine differences in loads of fecal bacteria, Escherichia coli and Salmonella spp., in runoff from conventional tillage (CT) and no-till (NT) systems after herbicides were watered into an Ultisol fertilized with broiler litter. On replicated 6 m 2 -plots ( n = 3) simulated rainfall was applied for 70 min with composite runoff samples collected every 5 min and analyzed for E. coli and Salmonella spp. Although total runoff volume from the CT plots was significantly greater than from NT plots, no significant differences in total load of E. coli and Salmonella or the percent of total loads of E. coli and Salmonella recovered in runoff between tillage systems were observed. Total percentage of Salmonella recovered in runoff from both tillage systems was, however, four log 10 orders of magnitude greater than the percentage of E. coli that was recovered. Difference in percentage recovered between the fecal indicator bacterium, E. coli , and the pathogen, Salmonella , underscores an apparent difference in hydrologic transport characteristics of these two fecal bacteria and casts doubts on the efficacy of E. coli as an indicator of risk to public health.

Many parasitoids require food resources, such as nectar and pollen, besides hosts in order to optimize their life histories. This requirement has led to an interest in using these food resources in pest management. Here we assess the potential effects of two flowering plants, buckwheat (Fagopyrum esculentum Moench) and Indian blanket (Gaillardia pulchella Foug.), a 5% honey solution, and water (control) on the longevity and fecundity of Aridelus rufotestaceus (Tobias), an important parasitoid of stink bug, Nezara viridula (L.). G. pulchella and 5% honey solution significantly increased A. rufotestaceus fecundity compared to water (P = 0.017), with G. pulchella exhibiting the highest fecundity (138 ± 3 eggs), followed by 5% honey solution (134 ± 6 eggs), F. esculentum (123 ± 5 eggs), and water (109 ± 3 eggs). G. pulchella, F. esculentum, and 5% honey solution significantly increased longevity of A. rufotestaceus relative to water (P < 0.0001), with G. pulchella yielding the highest longevity (11 ± 1 d), followed by 5% honey solution (10 ± 1 d), F. esculentum (9 ± 1 d), and water (4 ± 0 d). Body sugars (fructose, glucose, sucrose and maltose) of A. rufotestaceus did not vary significantly among treatments after 24 h of parasitoid exposure to the treatments immediately after adult emergence. These results imply that F. esculentum and G. pulchella can benefit A. rufotestaceus for managing N. viridula.

The oil content and fatty acid composition of seed of 233 genebank accessions (total) of nine Capsicum species, and a single accession of Tubocapsicum anomalum, were determined. The physicochemical characteristics of oil extracted from seed of Capsicum annuum and Capsicum baccatum were also examined. Significant differences among mean values for seed oil content were detected among the cultivated Capsicum species. Oil content in seed of C. annuum var. annuum was significantly greater than that in seed of other cultivated species. Capsicum pubescens had the lowest average seed oil content. Among the non-cultivated taxa examined, seed of Capsicum galapagoense had the lowest oil content and T. anomalum the highest. Averages across the 5 cultivated taxa for the 4 principal fatty acids were 12.9%, 3.4%, 6.7% and 76.0% for C16:0 (palmitic), C18:0 (stearic), C18:1 (oleic) and C18:2 (linoleic), respectively. Linoleic acid was the principal fatty acid in all samples, with a high value of 81% in Capsicum chinense. Capsicum frutescens had the lowest percentage of total unsaturated fatty acids and T. anomalum the highest. In general, the oil content and fatty acid composition of seed of the wild taxa were similar to those of the cultivated species.

Nutrient inputs from urban encroachment and agricultural activities have been implicated in contributing to the environmental health decline and loss of organism diversity of South Florida ecosystems. Intensive agricultural pesticide use may also challenge these ecosystems. One possible mechanism is pesticide release to the atmosphere after application. The process is enhanced in this region due to the calcareous soils, frequent rainfall, and high humidity and temperatures. This study examined the atmospheric fate of the widely-used insecticide endosulfan. Air samples were collected over a five-year period (2001–2006) at a site within the agricultural community of Homestead, Florida and at sites located in nearby Biscayne and Everglades National Parks (NPs). Mean gas phase air concentrations of α-endosulfan were 17 ± 19 ng m−3 at Homestead, 2.3 ± 3.6 ng m−3 at Everglades NP, and 0.52 ± 0.69 ng m−3 at Biscayne NP. Endosulfan emissions from agricultural areas around Homestead appeared to influence air concentration observations at the NP sites. During an intensive sampling campaign, the highest total endosulfan concentrations at the NP sites were observed on days when air parcels were predicted to move from Homestead towards the sampling locations. The α-endosulfan fraction (α/(α + β)) was used to examine the contribution of pesticide drift versus volatilization to the overall residue level. The formulated product has an α fraction of approximately 0.7, whereas volatilization is predicted to have an α fraction of ≥0.9. The median α- fraction observed during periods of high agricultural activity at Homestead and Everglades NP was 0.84 and 0.88, respectively, and during periods of low agricultural activity the median at Homestead was 0.86, indicating contributions from drift. The median α fraction at Everglades NP was 1.0 during periods of low agricultural activity, while Biscayne NP was 1.0 year round indicating air concentrations are primarily influenced by regional volatilization.

Data on intra-specific variability for seed oil content, physical characteristics and fatty acid composition in Cucurbita moschata and Cucurbita argyrosperma are lacking in the scientific literature. We examined 528 genebank accessions of C. moschata and 166 accessions of C. argyrosperma – which included members of both subsp. argyrosperma and subsp. sororia – for seed oil content, oil physical characteristics and fatty acid composition. The oil of both species had near-identical viscosities, viscosity indices, colour and oxidative stabilities while the oil of C. argyrosperma had a slightly higher pour point, cloud point, percentage of free fatty acids and acid value when compared with C. moschata. Mean oil content values of the two species were similar at 28.7 ± /2.7 and 29.8 ± /2.6% for C. moschata and C. argyrosperma, respectively. The mean seed oil content of C. argyrosperma subsp. argyrosperma var. palmeri (32.1%) was significantly higher than that of the other taxa examined. The average (mean) percentage of total seed weight attributable to the kernel was 77.2% in C. moschata (n= 34) and 74.5% in C. argyrosperma (n= 46). The percentage of total seed weight attributable to the hull was correlated with seed oil content, in both species. Linoleic was the predominant fatty acid in all the samples analysed. Means for individual fatty acids in C. moschata were linoleic 48.5%, oleic 22.6%, palmitic 20.7% and stearic 7.5%. Means for individual fatty acids in C. argyrosperma were linoleic 47.3%, oleic 27.5%, palmitic 16.5% and stearic 8.0%.

In the Southeastern Coastal Plain (USA) farmers with access to irrigation commonly water in herbicides following their preemergence application to improve efficacy of the herbicide. This practice increases near surface soil water content and may promote increased runoff during subsequent storm events. The objective of our study was to determine differences in P and N runoff from conventional tillage (CT) and no tillage (NT) systems when herbicides were watered into loamy sand Ultisols fertilized with broiler litter. Simulated rain with variable intensity was applied for 70 min with runoff samples collected every 5 min and analyzed for total P and N, PO 4 3− , NH 4 + and NO 3 − . Results indicated the no-tillage treatment lost significantly more PO 4 3− and NH 4 + than the conventional tillage treatment. However, total P and N and NO 3 − runoff losses were significantly less in the no-tillage treatment. The proportion of total P and N leached through NT residues was 5.6% and 22% of the P and N applied as broiler litter, and the proportion of total P and N in runoff was 0.8% and 1.2% of the P and N applied in broiler litter. Overall 3.4 times more N and 2.7 more P were lost in runoff from the CT treatments than for the NT treatments. Reduced tillage was found to reduce N and P losses when combined with watering-in of surface applied broiler litter.

There is widespread interest in increasing conservation tillage use during row crop production. However, long-term hydrologic data are needed to better evaluate the potential benefits of conservation tillage. To that end, hydrologic monitoring was conducted for 11 years on a 1.2 ha hillslope located in the Atlantic Coastal Plain region of south central Georgia, USA. The site was equally divided between two tillage treatments, conventional-tillage (CT) and strip-tillage (ST), with cotton and peanut produced in rotation. Each tillage block was divided into three 0.2 ha plots to evaluate runoff as a function of tillage and slope position. Soil texture and hydraulic characteristic data were quantified to evaluate potential impacts on hydrologic processes including runoff, infiltration, and lateral subsurface flow. Surface runoff from CT averaged 22% of annual precipitation while that from ST averaged 13%. When paired by tillage and landscape position, annual runoff from ST was significantly less than annual runoff from CT (p = 0.025). Monthly surface runoff from CT was consistently greater than that from ST, particularly during May through August. Increased infiltration as a consequence of the reduced tillage led to significantly greater average annual subsurface losses from ST (19%) than from CT (10%) (p = 0.025). Results indicated that slope position and textural differences may also have influenced site hydrology. Plots at the top of the landscape where finer soil textures were observed produced greater runoff than plots at lower landscape positions where coarser textures were observed. In summary, the ST cotton/peanut rotation can be expected to significantly reduce runoff but increase lateral subsurface flow. As a consequence, water budgets from the two tillage systems were essentially equal. Similar decreases in surface runoff and increases in lateral subsurface flow can be expected to occur in landscapes in the Atlantic Coastal Plain Region where strip tillage is adopted.

Assessment of erosion impact on soil carbon and nitrogen loss and redistribution within landscapes is needed to develop estimates of soil carbon sequestration potential, soil quality management plans, and to evaluate potential for transport of sediment bound agrochemicals. We used variable intensity rainfall simulations to quantify the effects of tillage, conventional and strip, and antecedent soil water content on sediment-bound carbon and nitrogen loss from a Tifton loamy sand located in the southeastern Atlantic Coastal Plain (USA). Carbon and nitrogen loss via erosion of silt + clay sized versus sand sized sediment particles were quantified. Antecedent water content had no effect on mean sediment loss within tillage treatments, but losses from conventional till treatments were significantly greater than from strip till. Sediment lost as silt + clay was from 58 to 78% of the total under conventional and from 30 to 39% under strip tillage. The fraction of sediment lost as silt + clay versus sand was greater under conventional tillage than under strip tillage. Within-event sediment carbon enrichment compared to the top 2 cm of soil was 0.9–7.2 for conventional and 0.6–3.7 for strip tillage. The strip till silt + clay fraction had significantly higher carbon content than the strip till sand fraction and the conventional till silt + clay fraction. Carbon loss from treatments was directly proportional to sediment loss. However, the conventional till treatments lost 4.6–6 times more carbon from the silt + clay sized fraction and 1.9–4.8 times more carbon from the sand sized fraction than strip till treatments. Results suggest that the higher proportion of silt + clay fraction sediment loss from conventional till may deplete nitrogen enriched organic matter while decreased erosion from strip till may serve to increase retention of organic nitrogen. Findings also indicate that an approach that adjusts loss estimates of organic carbon and nitrogen by using wet-sieved subsamples for analysis followed by standardization against total bulk sediment loss accounts for introduced errors from both sub-sampling efficiency and disturbance.

The majority of peanut production in Georgia is in the Coastal Plain region where sandy soils and relatively high rainfall (∼1250 mm/yr) provide a favorable environment for the crop. Coastal Plain soils have traditionally been cropped under conventional tillage practices; and are susceptible to runoff, sediment, and chemical losses from short duration-high intensity, runoff producing storms. We quantified infiltration, runoff, and sediment losses from a Tifton loamy sand managed under conventional- (CT) and strip- (ST) tillage systems and planted to peanut at three times during a growing season with simulated rainfall that utilized variable rainfall intensities representative of each time period (spring, summer, fall). In 2008, a field study was established with CT and ST systems each planted to single-row peanut. Simulated rainfall was applied at planting, 30 days after planting, and after peanut harvest with rainfall events comprised of variable intensity (Iv) patterns representative of each time or season (spring = IvSPR, summer = IvSUM, fall = IvFALL). Simulated rainfall was applied to 6-m2 plots (n = 3) for each treatment with runoff (R) and sediment (E) yields measured from each plot. Overall, runoff and infiltration from CT and ST plots was 9–22% and 78–91% of the total rainfall applied, respectively. The most runoff occurred from CT-IvFALL plots; the least from ST-IvSUM plots. Sediment yields from CT and ST plots ranged from 105–1419 kg/ha. The most sediment occurred from CT-IvSPR plots; the least from ST-IvSUM plots. The most runoff and sediment per unit of rainfall applied occurred from CT-IvFALL plots. Rainfall intensity and runoff from CT and ST plots for IvSPR, IvSUM, and IvFALL events were correlated (r = 0.73–0.95). Runoff and sediment yield from CT and ST plots for IvSPR, IvSUM, and IvFALL events were also correlated (r = 0.66–0.99). Values of Rmax for CT and ST plots were 7–20% of the maximum intensity for their respective Iv events. Values of Rmax and Emax for CT and ST plots occurred 3–8 min after the maximum intensity for their respective events. The CT plots averaged 60% more runoff, 86% higher Rmax values, 3.3-fold more sediment, and 3.7-fold higher Emax values than ST plots. Maximum difference between CT and ST plots for runoff (2.4-fold), Rmax (2.7-fold), and sediment (3.8-fold) was for IvFALL events; maximum difference between CT and ST plots for Emax (5.6-fold) was for IvSUM events. Results show the pronounced effect of three rainfall intensity patterns and tillage on runoff and sediment losses from critical times (planting, first fungicide application ∼30 days after planting, after harvest) during a peanut growing season. Understanding the magnitude of runoff and sediment losses help define “windows of risk” and how conservation tillage can reduce those losses and help producers manage natural resources and agrichemical losses from peanut cropping systems.

Intensive glyphosate use has contributed to the evolution and occurrence of glyphosate-resistant weeds that threaten production of many crops. Sustained use of this highly valued herbicide requires rotation and/or substitution of herbicides with different modes of action. Cotton growers have shown considerable interest in the protoporphyrinogen oxidase inhibitor, fomesafen. Following registration for cotton in 2008, use has increased rapidly. Environmental fate data in major use areas are needed to appropriately evaluate risks. Field-based rainfall simulation was used to evaluate fomesafen runoff potential with and without irrigation incorporation in a conventional tillage system (CT) and when conservation tillage (CsT) was practiced with and without cover crop residue rolling. Without irrigation incorporation, relatively high runoff, about 5% of applied, was measured from the CT system, indicating that this compound may present a runoff risk. Runoff was reduced by >50% when the herbicide was irrigation incorporated after application or when used with a CsT system. Data indicate that these practices should be implemented whenever possible to reduce fomesafen runoff risk. Results also raised concerns about leaching and potential groundwater contamination and crop injury due to rapid washoff from cover crop residues in CsT systems. Further work is needed to address these concerns.

The highly weathered, low-carbon, intensively cropped, drought-prone Coastal Plain soils of Georgia are susceptible to runoff and soil loss, especially at certain times of the year when soil water contents are elevated. We quantified the effects of antecedent water content (AWC) on runoff ( R ) and sediment ( E ) losses from two loamy sands managed under conventional- (CT), strip- (ST), and/or no-till (NT) systems. Two AWC treatments were evaluated: field moist (FM) and pre-wet (PW), created with and without post pesticide application irrigations (∼12 mm of water added with the rainfall simulated over 30 min) for incorporation. Treatments (5) evaluated were: CT + FM, CT + PW, ST + FM, ST + PW, and NT + PW. Field plots, each 2-m × -3 m, were established on each treatment. Each 6-m 2 field plot received simulated rainfall at a variable rainfall intensity ( I v ) pattern for 70 min (site 1) or a constant rainfall intensity ( I c ) pattern for 60 min (site 2; I c = 50.8 mm h −1 ). Adding ∼12 mm of water as herbicide incorporation increased AWCs of the 0–2 (3–9-fold) and 2–15 (23–117%) cm soil depths of PW plots compared to existing field moist soil conditions. Increase in AWC increased R (as much as 60%) and maximum R rates (as much as 62%), and decreased E (at least 59%) and maximum E rates (as much as 2.1-fold) for corresponding tillage treatments. Compared to CT plots, ST and NT plots decreased R (at least 2.6-fold) and maximum R rates (as much as 3-fold), and decreased E (at least 2.7-fold) and maximum E rates (at least 3.2-fold). Runoff curves for pre-wetted CT and ST plots were always higher than corresponding FM curves, whereas E curves for field moist CT and ST plots were always higher than corresponding PW curves. Changes in AWC and tillage affected detachment and transport processes controlling runoff and sediment yields. A more accurate measure of rainfall partitioning and detachment and transport processes affecting R and E losses was obtained when commonly occurring field conditions (increased AWC with irrigation; I v pattern derived from natural rainfall; commonly used tillage systems) were created and evaluated.

Pesticides are typically applied as mixtures and or sequentially to soil and plants during crop production. A common scenario is herbicide application at planting followed by sequential fungicide applications post-emergence. Fungicides depending on their spectrum of activity may alter and impact soil microbial communities. Thus there is a potential to impact soil processes responsible for herbicide degradation. This may change herbicide efficacy and environmental fate characteristics. Our study objective was to determine the effects of 4 peanut fungicides, chlorothalonil (2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile), tebuconazole (alpha-[2-(4-chlorophenyl)ethyl]-alpha-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol), flutriafol (alpha-(2-fluorophenyl)-alpha-(4-fluorophenyl)-1H-1,2,4-triazole-1-ethanol), and cyproconazole (alpha-(4-chlorophenyl)-alpha-(1-cyclopropylethyl)-1H-1,2,4-triazole-1-ethanol) on the dissipation kinetics of the herbicide, metolachlor (2-chloro-N-(6-ethyl-o-tolyl)-N-[(1RS)-2-methoxy-1-methylethyl]acetamide), and on the soil microbial community. This was done through laboratory incubation of field treated soil. Chlorothalonil significantly reduced metolachlor soil dissipation as compared to the non-treated control or soil treated with the other fungicides. Metolachlor DT(50) was 99 days for chlorothalonil-treated soil and 56, 45, 53, and 46 days for control, tebuconazole, flutriafol, and cyproconazole-treated soils, respectively. Significant reductions in predominant metolachlor metabolites, metolachlor ethane sulfonic acid (MESA) and metolachlor oxanilic acid (MOA), produced by oxidation of glutathione-metolachlor conjugates were also observed in chlorothalonil-treated soil. This suggested that the fungicide impacted soil glutathione-S-transferase (GST) activity. Fungicide DT(50) was 27-80 days but impacts on the soil microbial community as indicated by lipid biomarker analysis were minimal. Overall study results indicated that chlorothalonil has the potential to substantially increase soil persistence (2-fold) of metolachlor and alter fate and transport processes. GST mediated metabolism is common pesticide detoxification process in soil; thus there are implications for the fate of many active ingredients.

Soil microbial lipid biomarkers are indicators of viable microbial biomass and community structure. Pressurized liquid extraction (PLE) of soil phospholipid fatty acids (PLFA) and neutral lipid fatty acids (NLFA) was compared to a conventional extraction method in four soils with differing physical and chemical properties. PLE efficiency was greater than that of the conventional method for about half of the saturated PLFA and for selected other Gram-positive (i16:0) and Gram-negative bacteria (18:1omega7c) PLFA, fungal PLFA (18:2omega6,9c), and eukaryotic NLFA from a coarse-textured soil. Lipids extracted by the two methods did not indicate a significant difference in microbial community structure data. Principle component analysis revealed that PLFA clustered by location, with data indicating that the group of microbes contributing the greatest weight differed among soils. Overall, the PLE method proved to be more efficient at extracting soilborne microbial lipids while not altering microbial community information. These advantages indicate the PLE method is robust and well-suited to soil microbial ecology research.

Flurprimidol is a plant growth regulator that can be applied as a granular formulation. Understanding flurprimidol release from a granular formulation and movement in various mediums will impact how it is used. Dissipation of flurprimidol from a granular formulation and movement through organic media and sand were evaluated in a greenhouse and laboratory experiment. Experimental variables included media type, depth, and irrigation event. Dissipation isotherms were determined by applying nonlinear regression. Mobility was evaluated using columns filled with media, which was surface-spiked with the granular formulation and then irrigated once daily for 22 consecutive days. Leachate was collected and analyzed by high-performance liquid chromatography–mass spectroscopy. Half-life (DT50), defined as time to 50% reduction, varied among sand, media, and media depth. Flurprimidol dissipation was rapid through sand with DT50 of 6 days. DT50 increased with increasing media depth from 5 to 10 cm for pine bark plus sand, 18 and 35 days, and hardwood bark plus sand, 77 and 173 days, respectively. Maximum flurprimidol leaching was a cumulative 71% of applied amounts over 22 irrigation events through the sand. Hardwood and pine bark media allowed less than 25% of flurprimidol to escape through the column. Data for all media indicated that flurprimidol was mobile through the substrates but exhibited hysteresis with pine bark and hard wood bark media. An initial pulse of flurprimidol will release slowly from this formulation over time. These results indicate that flurprimidol will dissipate from a granular formulation over time and that it will have movement through sand soil and pine bark and hardwood bark media to reach the roots of growing plants.

Most studies on plant-herbivore interactions focus on either root or shoot herbivory in isolation, but above- and belowground herbivores may interact on a shared host plant. Cotton (Gossypium spp.) produces gossypol and a variety of other gossypol-like terpenoids that exhibit toxicity to a wide range of herbivores and pathogens. Cotton plants also can emit herbivore-induced volatile compounds at the site of damage and systemically on all tissues above the site of damage. As these volatile compounds attract natural enemy species of the herbivore, they are thought to represent an indirect plant defense. Our study quantified gossypol and gossypol-like compounds in cotton plants with foliage feeding (Heliocoverpa zea), root feeding (Meloidogyne incognita), or their combination. Cotton plants with these treatments were studied also with respect to induced local and systemic volatile production and the attraction of the parasitic wasp Microplitis croceipes to those plants. We also evaluated whether foliage or root feeding affected foliar nitrogen levels in cotton. After 48 hr of leaf feeding and 5 wk of root feeding, local and systemic induction of volatiles (known to attract parasitoids such as M. croceipes) occurred with herbivore damage to leaves, and it increased in levels when root herbivory was added. Nevertheless, M. croceipes were equally attracted to plants with both leaf and root damage and leaf damage only. In contrast to previous studies in cotton, production of gossypol and gossypol-like compounds was not induced in leaf and root tissue following foliage or root herbivory, or their combination. We conclude that root feeding by M. incognita has little influence on direct and indirect defenses of Gossypium hirsutum against insect herbivory.

Bryostatin structures share a commonality of a central bryophan ring, but each differs due to two groups (R(1) and R(2)) that are attached to the bryophan ring via ester bonds. This research examines the impact that conditions such as UV light, acidic and basic conditions can have on the bryostatin structure in the presence of octanoic acid and water. Mass spectrometry (MS) measurements suggest that bryostatin can easily rearrange into various structures under natural conditions by reacting with carboxylates that are ubiquitous in nature. A second set of measurements suggest bryostatin can be hydrolyzed by water, a reaction that has significant implications in both medicinal applications and extraction procedures.

The impacts of a leguminous summer cover crop (sunn hemp; Crotalaria juncea) on nitrogen leaching from a corn (Zea mays L.) field was evaluated by direct measurements of soil water content and nitrogen balance components, complemented by direct and inverse modeling as an exploratory tool to better understand water flow and nitrogen balances in the soil. Water and nitrogen inputs and outputs were measured during winter corn production in an experimental field located in the south Miami-Dade basin in southern Florida (USA). Data from the last two seasons (2001‐2002 and 2002‐2003) of a 4-year study are presented. The field was divided into six 0.13 ha plots. One-half of the plots were rotated with sunn hemp (CC plots) during the summer while the remaining plots were kept fallow (NC plots). Sweet corn management was uniform on all plots and followed grower recommended practices. A numerical model (WAVE) for describing water and agrochemical movement in the soil was used to simulate water and nitrogen balances in both types of plots during the corn seasons. The hydrodynamic component of WAVE was calibrated with soil water data collected continuously at three depths, which resulted in accurate soil water content predictions (coefficients of efficiency of 0.85 and 0.91 for CC and NC plots, respectively). Measured components of the nitrogen balance (corn yields, estimated nitrogen uptake, and soil organic nitrogen) were used to positively assess the quality of the nitrogen simulation results. Results of the modeled water balance indicate that using sunn hemp as a cover crop improved the soil physical conditions (increase in soil water retention) and subsequently enhanced actual crop evapotranspiration and reduced soil drainage. However, nitrogen simulation results suggest that, although corn nitrogen uptake and yields were slightly higher in the CC plots than in the NC plots, there were net increases of soil N content that resulted in increased N leaching to the shallow aquifer. Therefore, the use of sunn hemp as cover crop should be coupled with reductions in N fertilizer applied to the winter crop to account for the net increase in soil N content.

The USDA Natural Resource Conservation Service curve number (CN) method for estimating surface runoff is frequently used in natural resource modeling. Water yield and subsequently water quality estimates depend heavily on CN selection. This study was conducted to estimate CNs for a cotton-peanut rotation under conventional and strip tillage (ST) methods for growing and dormant seasons. A comparison between alternative methods for calculating CN and their applicability was also made. Rainfall-runoff data measured from 1999 to 2005 at a field study site in South Georgia were used to calculate CNs by averaging, lognormal, and data-censoring methods. For conventional and STs, CNs by the averaging method using year-round data were 89 and 84, respectively, and by the lognormal method were 89 and 83, respectively. Results from the data-censoring method were 81 and 75, respectively, which matched standard table values developed from a long-term series of annual maximum runoff. Values were also found to vary by season. Curve numbers by the lognormal method for ST were 83 and 88 for growing and dormant seasons, respectively; however, there was no difference between growing and dormant seasons, 89, for conventional tillage. The corresponding CNs by the data-censoring method for ST were 71 and 79 for growing and dormant seasons, respectively, and for conventional tillage were 82 and 79 for growing and dormant seasons, respectively. Based upon errors of the estimates, runoff estimates showed no improvement when separate CNs for the two seasons were used. The data-censoring method CNs yielded lower runoff estimate errors than CNs obtained by the lognormal method. The data-censoring method is recommended for determining CNs from plot rainfall-runoff data pairs.

Runoff from farm fields is a common source of herbicide residues in surface waters. Incorporation by irrigation has the potential to reduce herbicide runoff risks. To assess impacts, rainfall was simulated on plots located in a peanut (Arachis hypogaea L.) field in Georgia's Atlantic Coastal Plain region after pre-emergence application of metolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)-N-[(1S)-2-methoxy-1-methylethyl]-acetamide) and pendimethalin (N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitro-benzenamine). Runoff, sediment, and herbicide loss as function of strip tillage (ST) versus conventional tillage (CT) were compared with and without irrigation (12.5 mm) after application of an herbicide tank mixture. For the CT system, metolachlor runoff was reduced 2x and pendimethalin 1.2x when compared with the non-irrigated treatment. The difference in irrigated and non-irrigated metolachlor means was significant (P = 0.05). Irrigation reduced metolachlor runoff by 1.3x in the ST system, but there was a 1.4x increase for pendimethalin. Overall results indicated that irrigation incorporation reduces herbicide runoff with the greatest impact when CT is practiced and products like metolachlor, which have relatively low K(oc) and high water solubility, are used. The lower ST system response was likely due to a combination of spray interception and retention by the ST system cover crop mulch and higher ST soil organic carbon content and less total runoff. During the study, the measured K(oc) of both herbicides on runoff sediment was found to vary with tillage and irrigation after herbicide application. Generally, K(oc) was higher for ST sediment and when irrigation incorporation was used with the CT system. These results have significant implications for simulation model parametization.

The low-carbon, intensively cropped Coastal Plain soils of Georgia are susceptible to runoff, soil loss, and drought. Reduced tillage systems offer the best management tool for sustained row crop production. Understanding runoff, sediment, and chemical losses from conventional and reduced tillage systems is expected to improve if the effect of a variable rainfall intensity storm was quantified. Our objective was to quantify and compare effects of a constant (Ic) intensity pattern and a more realistic, observed, variable (Iv) rainfall intensity pattern on runoff (R), sediment (E), and carbon losses (C) from a Tifton loamy sand cropped to conventional-till (CT) and strip-till (ST) cotton (Gossypium hirsutum L.). Four treatments were evaluated: CT-Ic, CT-Iv, ST-Ic, and ST-Iv, each replicated three times. Field plots (n=12), each 2 by 3 m, were established on each treatment. Each 6-m2 field plot received simulated rainfall at a constant (57 mm h(-1)) or variable rainfall intensity pattern for 70 min (12-run ave.=1402 mL; CV=3%). The Iv pattern represented the most frequent occurring intensity pattern for spring storms in the region. Compared with CT, ST decreased R by 2.5-fold, E by 3.5-fold, and C by 7-fold. Maximum runoff values for Iv events were 1.6-fold higher than those for Ic events and occurred 38 min earlier. Values for Etot and Ctot for Iv events were 19-36% and 1.5-fold higher than corresponding values for Ic events. Values for Emax and Cmax for Iv events were 3-fold and 4-fold higher than corresponding values for Ic events. Carbon enrichment ratios (CER) wereor=1.0 for ST plots andor=1.0 for CT plots (except for first 20 min). Maximum CER for CT-Ic, CT-Iv, ST-Ic, and ST-Iv were 2.0, 2.2, 1.0, and 1.2, respectively. Transport of sediment, carbon, and agrichemicals would be better understood if variable rainfall intensity patterns derived from natural rainfall were used in rainfall simulations to evaluate their fate and transport from CT and ST systems.

South Florida's Miami-Dade agricultural area is located between two protected natural areas, the Biscayne and Everglades National Parks, subject to the costliest environmental restoration project in history. Agriculture, an important economic activity in the region, competes for land and water resources with the restoration efforts and Miami's urban sprawl. The objective of this study, understanding water quality interactions between agricultural land use and the shallow regional aquifer, is critical to the reduction of agriculture's potentially negative impacts. A study was conducted in a 4-ha square field containing 0·9 ha of corn surrounded by fallow land. The crop rows were oriented NW–SE along the dominant groundwater flow in the area. A network of 18 monitoring wells was distributed across the field. Shallow groundwater nitrate–nitrogen concentration [N-NO3−] was analyzed on samples collected from the wells biweekly for 3 years. Detailed hydrological (water table elevation [WTE] at each well, groundwater flow direction [GwFD], rainfall) and crop (irrigation, fertilization, calendar) data were also recorded in situ. Flow direction is locally affected by seasonal regional drainage through canal management exercised by the local water authority. The data set was analyzed by dynamic factor analysis (DFA), a specialized time series statistical technique only recently applied in hydrology. In a first step, the observed nitrate variation was successfully described by five common trends representing the unexplained variability. By including the measured hydrological series as explanatory variables the trends were reduced to only three. The analysis yields a quantification of the effects of hydrological factors over local groundwater nitrate concentration. Furthermore, a spatial structure across the field, matching land use, was found in the five remaining common trends whereby the groundwater [N-NO3−] in wells within the corn rows could be generally separated from those in fallow land NW and SE of the crop strip. Fertilization, masked by soil/water/plant-delayed processes, had no discernible effect on groundwater nitrate levels. Copyright © 2006 John Wiley & Sons, Ltd.

An interlaboratory study was conducted at 8 locations to assess the stability of pesticides on solid-phase extraction (SPE) disks after incubation at various temperatures and for various time intervals. Deionized water fortified with selected pesticides was extracted by using 2 types of SPE filtration disks (Empore C18 and Speedisk® C18XF), and after extraction, the disks were incubated at 3 temperatures (25, 40, and 55C) and for 2 time intervals (4 and 14 days). Deionized water was fortified with atrazine, carbofuran, and chlorpyrifos by all participating laboratories. In addition, some of the laboratories included 2 of the following pesticides: metolachlor, metribuzin, simazine, chlorothalonil, and malathion. Concurrently, fortified water samples were extracted with the incubated samples by using each disk type at 4 and 14 days. Pesticides had equivalent or greater stability on ≤1 of the C18 disk types, compared with storage in water. The lowest recoveries of carbofuran (6%) and chlorpyrifos (7%) were obtained at 55C after storage for 14 days in incubated water. At 55C after 14 days, the lowest recovery for atrazine was 65% obtained by using Empore disks. Pesticide-specific losses occurred on the C18 disks in this study, underlining the importance of temperature and time interval when water is extracted at remote field locations and the SPE disks containing the extracted pesticides are transported or shipped to a laboratory for elution and analysis.

The peanut plant (Arachis hypogaea) is known to produce stilbene phytoalexins as a defensive response to fungal invasion; however, the distribution of phytoalexins among different organs of the peanut plant at early stages of growth under axenic conditions has not been studied. Axenic plants produced a stilbenoid, resveratrol, as well as soluble bound and free phenolic acids, including 4-methoxycinnamic acid, which is reported in peanuts for the first time. Neither resveratrol nor phenolic acids were found in the root mucilage; the prenylated stilbenes were restricted to the mucilage and were not found in other organs of the peanut plant. These findings may lead to a better understanding of the defensive role of peanut stilbenes and phenolic acids.

Pearl millet is widely consumed in regions of Africa and Asia, and is increasingly being grown as an alternative grain in drought-prone regions of the United States. Pearl millet and corn were grown in dryland conditions at Tifton, Georgia, USA and grains were compared for pre-harvest infection by potentially toxigenic fungi and contamination by mycotoxins. Corn hybrids Agripro 9909 and Pioneer 3146, and pearl millet Tifgrain 102 were grown in 2000 and 2001; pearl millet HGM 100 was included in the test in 2001. Hybrids were sown on multiple planting dates in each year to induce variation in flowering time. Host species differed in the frequency of isolation of potentially toxigenic fungal species in both years. Across years, corn hybrids were more prone to infection by Aspergillus flavus Link (maximum isolation frequency = 8.8%) and Fusarium moniliforme Sheldon sensu lato (maximum isolation frequency = 72.8%), with corresponding greater concentrations of aflatoxins (maximum concentration = 204.9 microg kg(-1)) and fumonisins (maximum concentration = 34,039 microg kg(-1)). Pearl millet was more prone to infection by F. semitectum Berk.Ravenel (maximum isolation = 74.2%) and F. chlamydosporum WollenwebReinking (maximum isolation = 33.0%), and contamination by moniliformin (maximum contamination = 92.1 microg kg(-1)). Beauvericin (maximum concentration = 414.6 microg kg(-1)) was present in both hosts. Planting date of corn affected aflatoxin and beauvericin contamination in 2000, and fumonisin concentration in 2001. The observed differences in mycotoxin contamination of the grains, which are likely due to host-specific differences in susceptibility to pre-harvest mycoflora, may affect food safety when the crops are grown under stress conditions.

Solid-phase extraction (SPE), gas chromatography electron capture detector (GC-ECD) and gas chromatography nitrogen-phosphorous detector (GC-NPD) and gas chromatography–mass spectroscopy (GC-MS) were applied for trace-level de-termination of 20 pesticides in river nile water. Samples were collected from March to October 2003 from different sites located in Greater Cairo, Egypt. First, extrac-tion by on-site solid-phase extraction of 1 liter from field and laboratory spiked and unspiked (raw river water) samples using poly-divinyl benzene-N-vinyl pyrolidine cartridge based sorbent. Next, water extracts were subject of analysis by GC-ECD and GC-NPD. Next, selected samples that were positive to GC-ECD or GC-NPD were analyzed by GC-MS in order to improve the determination of detected pesti-cides. Recoveries from laboratoy spiked samples were > 85% for 16 of the 20 com-pounds with % relative standard deviation (% RSD) in the 5 to 10 % range. The lowest recoveries were for aldrin, 52 % and prothiofos, 48 %. A similar trend was observed with p,p-DDE and p,p-DDT values. Field spike results also indicated high % recovery for most of the target compounds. Values were > 85% for 12 of the 20 analytes, as was the case in laboratory spikes, Aldrin, 54 % and prothiofos, 55 % yielded the lowest values. Overall field spike recovery reproducibility was lower since % RSDs were higher, 15-40 %. Overall results indicated a relatively high de-gree of accuracy and precision could be achieved for most of the target compounds by methods applied in present study.

Repeated application may increase rates of pesticide dissipation in soil and reduce persistence. The potential for this to occur was investigated for the fungicide, tebuconazole (alpha-[2-(4-chlorophenyl)ethyl]-alpha-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol), when used for peanut (Arachis hypogaea L.) production. Soil samples were collected from peanut plots after each of four tebuconazole applications at 2-wk intervals. Soil moisture was adjusted to field capacity as necessary and samples were incubated in the laboratory for 63 d at 30 degrees C. Untreated plot samples spiked with the compound served as controls. Results indicated accelerated dissipation in field-treated samples with the time to fifty percent dissipation (DT50) decreasing from 43 to 5 d after three tebuconazole applications. Corresponding increases in rates of accumulation and decay of degradates were also indicated. Best-fit equations (r2 = 0.84-0.98) to dissipation kinetic data combined with estimates of canopy interception rates were used to predict tebuconazole and degradates concentration in soil after each successive application. Predicted concentrations compared with values measured in surface soil samples were from twofold less to twofold greater. Use of kinetic data will likely enhance assessments of treatment efficacy and human and ecological risks from normal agronomic use of tebuconazole on peanut. However, the study indicated that varying soil conditions (in particular, soil temperature and water content) may have an equal or greater impact on field dissipation rate than development of accelerated dissipation. Results emphasize that extension of laboratory-derived kinetic data to field settings should be done with caution.

Climate and soil conditions in South Florida along with an extensive canal system facilitate movement of agricultural pesticides into surface waters. In a two-year study (2002-2004) of the currently used pesticides in South Florida, atrazine, endosulfan, metolachlor, chlorpyrifos, and chlorothalonil were the most frequently detected in the canals and in Biscayne Bay, with average concentrations of 16, 11, 9.0, 2.6, and 6.0 ng/L, respectively. Concentrations of atrazine and chlorpyrifos were highest near corn production. Chlorothalonil and endosulfan concentrations were highest near vegetable production, with no clear trend for metolachlor, which is used on multiple crops. Concentration data were used to calculate an aquatic life hazard potential for the planting period (November) versus the harvest period (March). This analysis indicated that a higher hazard potential occurs during harvest, primarily from the use of endosulfan. These data will also serve to document canal conditions prior to implementation of the Comprehensive Everglades Restoration Plan (CERP).

Conservation tillage has significant potential as a water management tool for cotton production on sandy, drought-prone soils. Plant residue remaining at the soil surface from prior crops serves as a vapor barrier against water loss, reduces raindrop impact energy, slows surface runoff, and often increases infiltration. By increasing infiltration, the potential for greater plant-available water can be enhanced and irrigation requirements reduced. Five years of data were collected to quantify the hydrologic differences between strip till and conventional till production systems. Surface runoff and lateral subsurface flow were measured on six 0.2 ha plots in South Georgia in order to quantify the water-related effects of conservation tillage. Significant differences in surface and subsurface water losses were observed between the conventional and strip tilled plots. Surface runoff from the conventionally tilled plots exceeded that from the strip tilled plots, while subsurface losses were reversed. Surface runoff losses from the conventionally tilled plots exceeded those from the strip tilled plots by 81% (129 mm/year). Shallow lateral subsurface losses from the strip tilled plots exceeded those from the conventionally tilled plots by 73% (69 mm/year). Overall, a net annual gain of 60 mm of water was observed for the strip tilled plots.

The fungicide tebuconazole is widely used to control soil-borne and foliar diseases in peanuts and other crops. No published data are currently available on the extent and rate at which this compound degrades in soil. Unpublished data summarized in registration documents suggest that the compound is persistent, with 300-600 days half-life. We conducted a 63-day laboratory incubation to evaluate tebuconazole's dissipation kinetics and impact on soil microbial activity in Tifton loamy sand. Tifton soils support extensive peanut production in the Atlantic Coastal Plain region of Georgia and Alabama. Products containing tebuconazole are applied to an estimated 50% of the peanut acreage in the region. At the end of the incubation, 43 (+/-42)% of the parent compound was recovered in soil extracts. The first-order kinetic model, which gave a good fit to the dissipation data (r2 = 0.857), yielded a soil half-life (t1/2) of 49 days. This is 6-12 times more rapid than t1/2 values described in unpublished tebuconazole registration documents. Four degradates were identified. Tentative structural assignments indicated that degradates were derived from hydroxylation of the parent compound and/or chlorophenyl ring cleavage. Cleavage products showed a steady increase during the incubation, and on a molar basis were equal to 63% of the time zero tebuconazole concentration. No significant effect on soil microbial biomass was observed, indicating that when the compound is applied at normal agronomic rate it does not impact soil metabolic activity. Use of the soil-half life data derived in this study should improve the accuracy oftebuconazole fate assessments for Coastal Plain peanut production. The study also indicated that environmental assessment of selected degradates may be needed to fully evaluate risks of tebuconazole use.

Gonadal intersex and high prevalences of the female phenotype have been observed in fish populations in urbanized areas. Environmental estrogens discharged in sewage treatment plant effluents may be responsible for feminization of fish but many compounds with the potential to induce these responses occur in effluents, including natural and synthetic estrogen hormones, degradation products of alkylphenol ethoxylate surfactants, and plasticizers. In this study, the estrogen hormones 17α-ethinylestradiol, 17β-estradiol, estrone, and estriol induced intersex (i.e., testis-ova) and altered sex in Japanese medaka (Oryzias latipes) when these fish were exposed to nanogram per liter concentrations of test compounds from hatch to approximately 100 d after hatch. A mix of nonylphenol mono- and diethoxylate induced a weak response and a mix of nonylphenol mono- and diethoxycarboxylate did not give a response in this assay at microgram per liter concentrations, indicating that these degradation products of nonylphenol ethoxylates have little or no estrogenic activity in fish. Bisphenol A induced testis-ova in medaka exposed to a concentration of 10 μg/L, but diethylhexyl phthalate did not induce a response. Results with the medaka assay were consistent with estrogenic responses in the yeast estrogen screening assay. Analyses of monitoring data reported in the literature indicate that concentrations of estrogen hormones detected in the final effluents of sewage treatment plants are generally greater than the lowest-observed-effect levels for alterations to gonadal development in medaka.

Cerro Negro bitumen, separated from an Orimulsion sample, was incubated for up to 120 days with sediments collected at a petroleum-impacted site in Tampa Bay, Florida. Biodegradation conditions were optimized by increasing bitumen surface area, continuous agitation on a shaker apparatus, use of a complete growth medium, and maintenance at 37 degrees C. Aerobic degradation conditions were promoted by maintaining sediment contact with the laboratory atmosphere. Bitumen recovered in solvent extracts when compared to autoclaved controls decreased by up to 40% during the first 56 days. There was no detectable change after this. Molasses addition and use of a culture enriched from the sediments did not change the extent or rate of decrease in bitumen recovery. Chemical fractionation of bitumen control and degraded bitumen showed that aromatic and aliphatic fractions were depleted by approximately equals 50%. Accumulation of polars was observed; however, the apparent increase was relatively small when compared to the mass loss of the other fractions. Selected biomarker ratios were not affected by incubation indicating their utility for fingerprinting the source bitumen in environmental samples. PAH distribution in the aromatic fraction favored the higher alkyl-homologues with the relative degree of alkylation increasing as the mass of bitumen recovered decreased with degradation. The study showed that up to 40% of the bitumen was bioaccessible and that bioremediation may be a treatment option for sediments contaminated with bitumen by an Orimulsion spill.

The static die-away of the nonylphenol ethoxylate (NPE) surfactant used to stabilize the bitumen−water emulsion in the fuel Orimulsion was studied using estuarine water samples collected at four stations in Tampa Bay, FL. Incubations were in the dark at 28 °C for 183 days. Primary degradation was complete in 4−24 days with lag periods between 0 and 12 days. The concentration of five NPE intermediate degradation products and total surfactant were monitored at 4−8-day intervals for the first 89 days and at 30-day intervals thereafter. The intermediates detected included nonylphenol diethoxylate (NP2EO) and nonylphenoxy ethoxy acetic acid (NP2EC). Much smaller amounts of nonylphenoxy acetic acid (NP1EC) and nonylphenol monoethoxylate (NP1EO) were detected. The completely deethoxylated metabolite nonylphenol (NP) was not detected. On a molar basis, NP2EC accounted for 66.0−93.3% of degradation products and for 22.7−75.6% of the starting material at the termination of the experiment. The sequence of degradatio...

Lead and cadmium were measured in raw Nile River water and in finished drinking water at four treatment plants in Greater Cairo, Egypt. Samples were collected monthly during the period September 1993 to August 1994. The river water mean concentrations were 29.6 ± 8.74 μg/L for lead and 4.15 ± 0.88 μg/L for cadmium. These levels were 14 and 24 times less than levels reported in a study published in 1995 (Gomaa 1995). In the drinking water, the means were 9.93 ± 0.5 μg/L for lead and 2.2 ± 0.63 μg/L for cadmium. The drinking water mean concentrations were below internationally-recognized drinking water standards. Comparison of the raw and finished drinking water data showed that the water treatment facilities reduced concentrations of lead by 33% and cadmium by 53%.

A toxicologically based predictive scheme is presented for quantitatively ranking chemical agents with respect to their capacity to ensure endocrine disruption in target species based on short-term bioassays. Criteria providing the predictive framework include: (1) endocrine disruption as a multistage process, (2) phylogenetic considerations, (3) model system, and (4) estrogenic potency. Relative rankings were calculated for 15 environmentally relevant agents reported to have endocrine-disrupting effects. The relative ranking process offers a procedure for assessing the potential of endocrine disruption and for identifying data gaps for specific chemical agents. Although the current scheme is limited to “estrogenic” agents, it is anticipated that future refinements (e.g., incorporation of antiestrogenic potency data) will improve the system.

The atmosphere is an important transport route for semi-volatile pesticides like endosulfan. Deposition, which depends on physical-chemical properties, use patterns, and climatic conditions, can occur at local, regional, and global scales. Adverse human and ecological impact may result. We measured endosulfan wet deposition in precipitation over a 4-year period within an area of high agricultural use in Southern Florida (USA) and in nearby Biscayne and Everglades National Parks. Endosulfan's two isomers and degradate, endosulfan sulfate, were detected at high frequency with the order of detection and concentration being β-endosulfan>α-endosulfan>endosulfan sulfate. Within the agricultural area, detection frequency (55 to 98%) mean concentrations (5 to 87 ng L(-1)) and total daily deposition (200 ng m(-2) day(-1)) exceeded values at other sites by 5 to 30-fold. Strong seasonal trends were also observed with values at all monitored sites significantly higher during peak endosulfan use periods when vegetable crops were produced. Relatively high deposition in the crop production area and observations that concentrations exceeded aquatic life toxicity thresholds at all sites indicated that endosulfan volatilization and wet deposition are of ecotoxicological concern to the region. This study emphasizes the need to include localized volatilization and deposition of endosulfan and other semi-volatile pesticides in risk assessments in Southern Florida and other areas with similar climatic and crop production profiles.