Anastasia E. M. Chirnside

Winter cover crops as a best management practice for reducing nitrogen leaching

The role of rye as a winter cover crop to reduce nitrate leaching was investigated over a three-year period on a loamy sand soil. A cover crop was planted after corn in the early fall and killed in late March or early April the following spring. No-tillage and conventional tillage systems were compared on large plots with irrigated corn. A replicated randomized block design experiment was conducted on small plots to evaluate a rye cover crop under no-tillage and conventional tillage and with commercial fertilizer, poultry manure and composted poultry manure as nitrogen fertilizer sources. Nitrogen uptake by the cover crop along with nitrate concentrations in groundwater and the soil profile (0–150 cm) were measured on the large plots. Soil nitrate concentrations and nitrogen uptake by the cover crop were measured on the small plots. There was no significant difference in nitrate concentrations in the groundwater or soil profile with and without a cover crop in either no-tillage or conventional tillage. Annual amounts of nitrate–N leached to the water-table varied from 136.0 to 190.1 kg/ha in 1989 and from 82.4 to 116.2 kg/ha in 1991. Nitrate leaching rates were somewhat lower with a cover crop in 1989, but not in 1990. There was no statistically significant difference in corn grain yields between the cover crop and non-cover crop treatments. The planting date and adequate rainfall are very important in maximizing nitrogen uptake in the fall with a rye cover crop. On the Delmarva Peninsula, the cover crop should probably be planted by October 1 to maximize nitrogen uptake rates in the fall. On loamy sand soils, rye winter cover crops cannot be counted on as a best management practice for reducing nitrate leaching in the Mid-Atlantic states.

Contamination of groundwater by triazines, metolachlor and alachlor☆

Abstract The movement of triazines (atrazine, simazine, cyanazine), metolachlor and alachlor were studied in continous irrigated corn in an Evesboro loamy sand soil. Both no-tillage and conventional tillage treatments were used. Atrazine and simazine were detected in the groundwater more frequently than cyanazine and metolachlor. Alachlor, atrazine and simazine moved rapidly to the groundwater if sufficient rainfall occurred shortly after they were applied. Alachlor concentrations ranged from 4.0 to 15.0 ppb and atrazine concentrations ranged from

Movement and degradation of triazines, alachlor, and metolachlor in sandy soils

Abstract Four experiments conducted over a nine‐year period are summarized. The movement of alachlor, atrazine, simazine, cyanazine, and metolachlor were studied in a Coastal Plain, Evesboro loamy sand soil that had a water table near the surface. In two experiments atrazine and simazine were detected more frequently in the groundwater than metolachlor and cyanazine. There was no large difference in pesticide transport between conventional tillage and no‐tillage. In another experiment alachlor was detected in approximately 20% of the groundwater samples from May to July over a three‐year period. Several samples were above the EPA drinking water standard of two parts per billion. In the fourth experiment, all five herbicides moved below the root zone after a simulated rainfall (75 mm) five days after they were applied. Alachlor was detected more frequently in the lysimeters and groundwater than the other four herbicides. The research indicates pesticides may move to shallow groundwater by macropore flow in...

Biodegradation of Aged Residues of Atrazine and Alachlor in a Mix-Load Site Soil by Fungal Enzymes

�� -diethyl-N[methoxymethyl]-acetanilide) in contaminated mix-load site soil utilizing an extracellular fungal enzyme solution derived from thewhiterotfungus,Phanerochaetechrysosporium,growninapackedbedbioreactor.Thirty-twopercentofATand54%ofALwere transformed in the biometers. The pseudo first-order rate constant for AT and AL biodegradation was 0.0882d −1 and 0.2504d −1 , respectively. The half-life (t1/2) for AT and AL was 8.0 and 3.0 days, respectively. Compared to AT, the initial disappearance of AL proceeded at a faster rate and resulted in a greater amount of AL transformed. Based on the net Co2 evolved from the biometers, about 4% of the AT and AL initially present in the soil was completely mineralized.

Wetland Biogeochemistry Techniques

Biogeochemistry is the scientific discipline that addresses the biological, chemical, physical, and geological processes that govern the composition of the natural environment, with particular emphasis placed on the cycles of chemical elements critical to biological activity. Biogeochemical assays may measure a specific elemental pool, determine the rate of a pathway, or address a surrogate of a biogeochemical process or an elemental pool. In this chapter, we have attempted to emphasize field techniques; however, some of the techniques have relatively standard laboratory components that are beyond the scope of this chapter. This chapter is not meant to be all inclusive. We have chosen to emphasize the cycling of carbon, nitrogen, phosphorous, sulfur, manganese, and iron. Some of these techniques are not appropriate for all types of wetlands, or may be appropriate for a seasonally saturated wetland only during part of the season. Some of the techniques are simple and rely on equipment available to most wetlands practitioners. Others, which utilize isotopic methodologies, require expensive sophisticated equipment. Some techniques, such as soil organic matter determination by loss on ignition, have been accepted as standard methods for decades. Others, such as the determination of dissolved organic matter represent recent advances in a rapidly evolving field of ultra-violet and fluorescence technology. Some techniques rely solely on direct field measurements; others rely on the incorporation of published data with field data. Apparent strengths and weaknesses of the various approaches, and wetland scenarios that would preclude the use or compromise the accuracy of a given technique are addressed.

Environmental Impact of Long Piers on Tidal Marshes in Maryland-Vegetation, Soil, and Marsh Surface Effects

Piers may impact the health of coastal wetlands by altering vegetation, soil organic matter accretion, and sediment deposition or erosion. Permit requests for piers have recently increased in the U.S. leading to concern by environmental regulatory agencies on potential impacts. In response, a project was conducted in Maryland to assess the impacts of long piers on plant communities, soils, and marsh surface characteristics. Twenty sites with piers and 20 control sites were assessed. Control sites and pier sites were similar with respect to soil types, marsh surface characteristics, and plant community composition. Shading consistently reduced vegetation density directly beneath piers and occasionally reduced vegetation density adjacent to piers. Shading favored Spartina alterniflora over Distichlis spicata, and Distichlis spicata over Spartina patens. Distribution of marsh surface components (high marsh, low marsh, mudflats, open water) was unaffected by proximity to piers. Direct evidence of pier effects on erosion or deposition was limited to the immediate vicinity of a few piers. In general, thickness of the organic horizons or that of the root mats was unaffected by proximity to a pier. We concluded that any effects of piers on vegetation or erosion were restricted to the close proximity of the piers.

Leaching of dicamba in a coastal plain soil

Abstract Dicamba leaching to groundwater was studied for three years on an Evesboro loamy sand soil. Dicamba was applied to conventional tillage and no‐tillage corn post‐emergence at a rate of 0.56 kg/ha. The first year, dicamba was detected in all of the monitoring wells, 12 days after it was applied. Concentrations ranged from 2.0 to 37.0 μg/L. A total of 54 mm of rainfall occurred in the 12 days. In years two and three, dicamba was detected infrequently in the groundwater. The highest concentration was 4.9 μg/L. Other researchers have also found dicamba will move below the root zone if sufficient rainfall or irrigation occurs before significant degradation occurs.

Degrad ation of Harmful Bacteria in Simulated Wastewater by the White Rot Fungus Pleurotus ostreatus

The white rot fungus Pleurotus ostreatus was analyzed as a potential biocontrol agent used to reduce the amount of coliform bacteria in simulated wastewater and storm water runoff. On water agar plates, Pleurotus ostreatus was seen to prey on bacterial colonies and completely consume them within 72 hours. Based on this principle, biocell reactors (BCR) were used to determine the effectiveness of spent mushroom compost (SMC) containing P. ostreatus to reduce the concentration of E.coli in simulated wastewater and stormwater runoff. After the first 12 hours, the overall concentrations in the live reactors began to decrease while the concentration in the dead control began to increase. After a subsequent uncontaminated rain event, the E.coli concentration in the dead controls increased exponentially while the overall concentrations in the live reactors decreased. The simulated wastewater effluent treatments, while having the lowest total concentration of E.coli, did not decrease over time. This suggests that the presence of the live fungus kills the adsorbed E.coli and that nutrient concentrations may play a significant role in the level of predation observed.

Biodegradation of a Food Processing Wastewater Utilizing Phanerochaete chrysosporium

Soybean hulls are processed into soy flour in a method similar to paper mill production. During the process, the soybean hull wastewater (SHW) is discharged into an anaerobic lagoon and then into an aeration basin. From there, it passes to a facultative lagoon before discharge. Even after this conventional treatment, the SHW has extremely high amounts of Total Kjeldahl Nitrogen (TKN), Chemical Oxygen Demand (COD) and a high pH. We have developed an attached growth, packed-bed bioreactor (PBR) containing the white rot fungus (WRF), Phanerochaete chrysosporium . This fungus secretes enzymes that catalyze oxidation reactions that result in degradation of recalcitrant compounds such as PCB, PCP, and pesticides. Previous studies utilizing the fungus in a bioreactor found that it could decolorize a polymeric dye. We hypothesize that the WRF could degrade the SHW and reduce the TKN and COD. We also assessed the effectiveness of pH adjustment of the SHW before introduction into the bioreactor. The objectives were to evaluate the ability of P. chrysosporium grown in a PBR to degrade the SHW containing high concentrations of TKN and complex organic compounds and to investigate the effectiveness of pH adjustment of the SHW before treatment in the PBR. The WRF in the PBR was fed an N-limited media for 5 days before introduction of the SHW. The effluent was sampled daily and measure for TKN, COD and pH. The pH adjusted wastewater was recycled through the PBR and the effluent was sampled daily and measure for TKN, COD and pH. Within 48 hours, 63% of the TKN and 37% of the COD was degraded. The pH of the effluent increased steadily from an initial pH of 4.88 to 8.59 at 24 hours. Within 72 hours, the effluent pH was equal to the influent pH. At this point, degradation within the PBR ceased. Continuous adjustment of pH during recycling of the wastewater within the PBR resulted in an increase in the amount of TKN and COD degraded. Over 90% of the TKN and approximately 33% of the COD was removed during treatment within the PBR. The pH of the SHW in the PBR had a significant effect on fungal degradation. The reduction of COD was more sensitive to pH changes than the reduction of TKN. With the improved pH control in the PBR during recycling events, a greater amount of TKN and COD were removed from the wastewater. These positive results indicate that treatment of recalcitrant wastewater with the WRF deserves further investigation.

Influence of best management practices on water quality in the appoquinimink watershed

Abstract Surface and ground‐water quality were monitored in the Appoquinimink Watershed as part of the Appoquinimink Rural Clean Water Project (RCW)). Surface water was monitored for seven years and ground water was monitored for three years. As part of the RCWP plan, conservation tillage, fertilizer management and pesticide management were the most widely used best management practices. Best management practices decreased total phosphorus and total suspended solids concentrations in surface water. The unfiltered ortho phosphorus as a percentage of total phosphorus increased. Nitrogen concentrations did not change over the seven year monitoring period. The BOD concentrations increased because of increased residues left on the surface from conservation tillage. Atrazine was detected in the shallow ground water at concentrations ranging from 1 to 45 μg/L. Aldicarb was only detected in one monitoring well. Nitrate concentrations were above 10 mg/L in some areas of the watershed.