Groundwater nitrate-N Concentrations Research Articles

NITRATE-N DISTRIBUTION AND TRENDS IN SHALLOW GROUNDWATER ON AN EASTERN COASTAL PLAINSWATERSHED

Nonpoint source pollution from agriculture has been a major concern, particularly where intensiveagricultural operations exist near environmentally sensitive waters. To address these nonpoint source pollution concerns, a Water Quality Demonstration Project (WQDP) was initiated on the Herrings Marsh Run (HMR) watershed in Duplin County, North Carolina. The WQDP was implemented to determine water quality benefits from voluntary adoption of improved management practices. In the WQDP, 84 groundwater monitoring well sites were established on 21 farms selected to represent the major farming practices on the watershed. On the HMR watershed, nitrate-N contamination of groundwater was not a wide spread problem. Seventy-four percent of the groundwater monitoring sites had nitrate-N less than the drinking water standard of 10 mg/L. Mean nitrate-N concentrations were below 10 mg/L on 16 of the 21 farms. Of the four farms with nitrate-N exceeding 10 mg/L, one farm had mean nitrate-N that exceeded 20 mg/L. This farm had an undersized and overloaded swine wastewater spray field. After the spray field was expanded and application rates were reduced, groundwater nitrate-N concentrations declined; but they continued to exceed 20 mg/L. Other farms with swine waste spray fields had mean groundwater nitrate-N concentrations <20 mg/L throughout the study period. Groundwater nitrate-N concentrations under row crops were <10 mg/L on all but two farms. Three of the four farms with nitrate-N concentrations exceeding 10 mg/L were in a subwatershed of the HMR that had the highest concentration of animal waste application and excess nitrogen applied. Of the 21 farms, three farms had a significant increasing trend in groundwater nitrate-N while four farms had a significant decreasing trend. The overloaded swine wastewater spray field had a significant decreasing nitrate-N trend. Most farms with concentrations less than 10 mg/L had no detectable trend in nitrate-N concentration during the study. These findings indicate that nitrate-N contamination of groundwater is not a widespread problem on the HMR watershed even though it is intensively farmed.

Environmental impacts of different nitrogen inputs on dairy farms and implications for the Resource Management Act of New Zealand

Nitrogen inputs and losses from white clover/ryegrass pastures grazed by dairy cows were measured over three years in a farmlet experiment near Hamilton, New Zealand. Three farmlets received nominal rates of nitrogen fertilizer of 0, 200 or 400 kg N ha −1 year −1. Nitrate leaching from the free-draining soil averaged 40, 81 and 152 kg N ha −1 year −1, respectively. The other main nitrogen losses/removals were in milk and transfer of excreta to lanes and the milking shed. Gaseous nitrogen losses were small but increased up to 5-fold with nitrogen fertilizer application. Groundwater nitrate-N concentrations increased with nitrogen application to an average of 19 mg l −1 in the 400 N farmlet. Data are discussed in relation to that for average dairy farms in New Zealand and European countries, and to the environmental implications for the Resource Management Act of New Zealand.

Effects of agricultural practices and vadose zone stratigraphy on nitrate concentration in ground water in Kansas, USA

Differences in nitrate-N concentrations in ground water in Kansas can be explained by variations in agricultural practices and vadose-zone stratigraphy. In northwestern Kansas, past use of a local stream for tailwater runoff from irrigation and high fertilizer applications for sugar-beet farming resulted in high nitrate-N concentrations (12–60 mg L−1; in both soil and ground water. Nitrogen isotope values from the soil and ground water range from +4 to +8‰, which is typical for a fertilizer source. In parts of south-central Kansas, the use of crop rotation and the presence of both continuous fine-textured layers and a reducing ground-water chemistry resulted in ground-water nitrate-N values of &amp;lt; 3 mg L−1;. The effects of denitrification in the vadose zone and ground water are indicated by enriched δ 15N values of +10 to +15‰. At a site study, irrigated continuous corn was grown on sandy soils with discontinuous fine-textured layers. Here, nitrate-N concentrations were often &amp;gt; 10 mg L−1; in both soil and grounwater. Nitrogen isotope values of +3 to +7‰ indicate a fertilizer source. Crop rotation decreased nitrate-N values in the shallow ground water (9 m). However, deeper ground water showed increasing nitrate-N concentrations as a result of past farming practices.

Effects of agricultural practices and vadose zone stratigraphy on nitrate concentration in ground water in Kansas, USA

Differences in nitrate-N concentrations in ground water in Kansas can be explained by variations in agricultural practices and vadose-zone stratigraphy. In northwestern Kansas, past use of a local stream for tailwater runoff from irrigation and high fertilizer applications for sugar-beet farming resulted in high nitrateN concentrations (12–60 mg L−1; in both soil and ground water. Nitrogen isotope values from the soil and ground water range from +4 to +8M߮, which is typical for a fertilizer source. In parts of south-central Kansas, the use of crop rotation and the presence of both continuous fine-textured layers and a reducing ground-water chemistry resulted in ground-water nitrate-N values of<3 mg L−1;. The effects of denitrification in the vadose zone and ground water are indicated by enriched δ 15N values of +10 to +15. At a site study, irrigated continuous corn was grown on sandy soils with discontinuous fine-textured layers. Here, nitrate-N concentrations were often>10 mg L-1; in both soil and grounwater.Nitrogen isotope values of +3 to +7a. indicate a fertilizer source. Crop rotation decreased nitrate-N values in the shallow ground water (9 m). However, deeper ground water showed increasing nitrate-N concentrations as a result of past farming practices.

Seventy five years of arthritis research at the Strangeways Research Laboratory: 1912-87.

<h3>ABSTRACT:</h3> Nitrate contamination of shallow groundwater has been widely documented in association with agriculture in the Coastal Plain region of the Chesapeake Bay watershed. Elevated groundwater nitrate levels limit the use of shallow groundwater for human consumption and also result in elevated nonpoint source nitrogen (N) loads to Chesapeake Bay via elevated stream base-flow nitrate concentrations. This study investigated the effects of cereal grain winter cover crops on nitrate leaching rates, profile nitrate storage, and nitrate concentrations in shallow groundwater in two field-scale watersheds planted continuously in corn (Zea mays L) from 1984 through 1996. Winter-fallow conditions were maintained following the 1984 through 1987 growing seasons and cereal rye (Secale cereale L.) as a cover crop was planted immediately after grain harvest from 1988 through 1996. Cover crop effects on nitrate leaching rates also were evaluated in continuous no-till corn plots from 1990 through 1995. Nitrate leaching losses from the root zone and recharge of ‘shallow aquifers occurred primarily during winter months under conditions of law evapotranspiration’. The potential for nitrate leaching losses was determined primarily by the availability of nitrate in the root zone at the onset of the winter groundwater recharge period. Rye winter cover crops planted after corn harvest consistently reduced nitrate-N concentrations in root zone leachate to less than 1 mg/L during most of the groundwater recharge period, and reduced annual nitrate leaching losses by approximately 80% relative to winter-fallow treatments. Shallow groundwater nitrate-N concentrations under long-term continuous corn production decreased from the 10 to 20 mg/L range to less than 5 mg/L after seven years of cover crop use. Cover crops appeared to increase corn yields under adverse growing season conditions, but limited residual nitrate availability during the growing season relative to winter-fallow settings. Cover crop growth was generally N limited, suggesting that increased N inputs would have little effect on nitrate leaching, but would increase cover crop contributions to soil carbon pools.