William F. Ritter

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.

Odour control of livestock wastes: State-of-the-art in North America

Abstract Odours from livestock wastes are a result of anaerobic decomposition. More than 75 specific odorous compounds have been identified. Odour producing compounds have been measured by gas chromatography, wet chemistry tests and organoleptic tests. Vapour dilution and liquid dilutions are the most popular methods for measuring odour strength and odour intensity. The scentometer and butanol olfactometer have been used to measure odours in the field. Odours can be controlled by changing the nature of the compound, inhibiting anaerobic decomposition of wastes or confining the odour. Site selection and management are also important considerations in odour control. Odours may originate from livestock buildings and feedlots, waste treatment or storage units or from land spreading. Odour control by chemicals is expensive because of the large amount of chemical required at frequent intervals for effective control.

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

A review of bioremediation of contaminated soils and groundwater

Abstract The paper discusses bioremediation of contaminated groundwater and soils. Research needs for bioremediation are also discussed. Forms of bioremediation practiced today are the microbiological approach, which involves augmentation of the contaminated site with one or more species of contaminant‐specific degrading organisms, and the microbial ecology approach, which involves adjusting certain physical and chemical factors at a site to enhance degradation. The microbial approach can be used at most sites. Contaminated soils may be bioremediated by in‐situ techniques, landfarming, composting or in slurry bioreactors. Anaerobic biodegradation may offer an effective alternative to aerobic in‐situ bioremediation for some compounds. Chlorinated aliphatic and hetercyclics have been degraded anaerobically. Peholeum hydrocarbons are the most easily bioremediated compounds. White rot fungus Phanerochaete chrysosporium will degrade many PAH compounds found in cresote. Bioremediation is also being used to reme...

Impact of dead bird disposal pits on ground-water quality on the Delmarva Peninsula

Abstract Ground-water quality around six existing dead bird disposal pits was monitored for ammonia, nitrates, chlorides, fecal coliforms and fecal streptococci. The disposal pits were located on Evesboro loamy sand, Sassafras sandy loam, Fallsington sandy loam and Klej loamy sand soils. Elevated ammonia concentrations were detected in the ground-water at three of the six existing disposal pits. Ammonia concentrations as high as 366 mg/l N were measured. Fecal coliform and fecal streptococcus concentrations were low. Over 70% of the sample did not contain fecal coliforms or fecal streptococci. Chloride concentrations were above normal levels in only one monitoring well at one of the disposal pits. Disposal pits that handle the normal mortality of a broiler grower should not cause any more ground-water contamination than an individual septic tank and soil absorption bed. If disposal pits are to be used in the future on the Delmarva Peninsula, they should be regulated.

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...

Reducing impacts of nonpoint source pollution from agriculture: A review

Abstract Nonpoint source pollution from agriculture affects both surface water and ground‐water quality. Water quality degradation is caused by erosion and sediment, animal wastes, fertilizers and pesticides. Best management practices that control runoff and erosion will reduce particulate nitrogen and phosphorus loads but may increase nitrate losses in subsurface drainage. Only applying enough nutrients to meet crop needs will reduce nitrogen and phosphorus losses. Nonpoint source pollution from animal agriculture may result from animals grazing, open animal confinement feedlots, and manure disposal areas. In most cases pollution from feedlots is greater than from manure application sites or grazing areas. Pesticides with solubilities of greater than 10 ppm are lost mainly in the water phase of runoff. Runoff and erosion control best management practices will reduce pesticide losses in surface runoff.

Nitrate leaching under irrigation in the United States—a review

Abstract The literature was reviewed for nitrate leaching under irrigation. The mass of nitrate leached is directly related to the percolation volume. Both water management and nitrogen management are important in controlling nitrate leaching. Applying only enough nitrogen fertilizer to meet yield goals, timing of nitrogen application and the use of slow release fertilizers are nitrogen management practices that will reduce nitrate leaching. There have been a number of nitrogen simulation models that have been developed, but there is a lack of field data to validate the models.

Water quality of agricultural coastal plain watersheds

Abstract Runoffs from six rural watersheds in the Coastal Plain were monitored over a period of five years. Nitrogen, phosphorus and COD loading rates were developed for all the watersheds and related to land use and soil type. The nitrogen, phosphorus and COD content of rainfall was also measured. Annual total nitrogen loading rates varied from 3·2 to 42·5 kg ha −1 and annual total phosphorus loading rates from 0·37 to 1·08 kg ha −1 . More than 50% of the nitrogen and phosphorus loads occurred in baseflow. Highest nitrogen loads occurred on watersheds with well drained soils. Higher phosphorus loading rates occurred during storm events on watersheds with poorly drained soils than with well drained soils. Nitrogen, phosphorus and COD contributed by rainfall was greater than the loading rates occurring in streamflow.

Effect of an anaerobic swine lagoon on groundwater quality in sussex county, delaware

Abstract An unlined two-stage anaerobic swine lagoon was monitored for 4 years. Groundwater quality samples were analyzed for NH 3 N, NO 3 N, organic N, Cl, COD and total P. The lagoon did not have a serious impact on groundwater quality. Nitrate concentrations in all of the monitoring wells around the lagoon did not increase above 10 mg liter −1 after waste was added to the lagoon. Highest NO 3 N concentrations were found in monitoring wells in a cultivated field located 120 m from the lagoon. Chloride, NH 3 N and organic N concentrations gradually increased in a monitoring well located in the berm between the two stages.