Tillage and nutrient source effects on water quality and corn grain yield from a flat landscape

Beneficial effects of leaving residue at the soil surface are well documented for steep lands, but not for flat lands that are drained with surface inlets and tile lines. This study quantified the effects of tillage and nutrient source on tile line and surface inlet water quality under continuous corn (Zea mays L.) from relatively flat lands (<3%). Tillage treatments were either fall chisel or moldboard plow. Nutrient sources were either fall injected liquid hog manure or spring incorporated urea. The experiment was on a Webster-Canisteo clay loam (Typic Endoaquolls) at Lamberton, MN. Surface inlet runoff was analyzed for flow, total solids, NO(3)-N, NH(4)-N, dissolved P, and total P. Tile line effluent was analyzed for flow, NO(3)-N, and NH(4)-N. In four years of rainstorm and snowmelt events there were few significant differences (p < 0.10) in water quality of surface inlet or tile drainage between treatments. Residue cover minimally reduced soil erosion during both snowmelt and rainfall runoff events. There was a slight reduction in mineral N losses via surface inlets from manure treatments. There was also a slight decrease (p = 0.025) in corn grain yield from chisel-plow plots (9.7 Mg ha(-1)) compared with moldboard-plow plots (10.1 Mg ha(-1)). Chisel plowing (approximately 30% residue cover) alone is not sufficient to reduce nonpoint source sediment pollution from these poorly drained flat lands to the extent (40% reduction) desired by regulatory agencies.     

Fertilizer source effect on ground and surface water quality in drainage from turfgrass

Nutrients in surface and ground water can affect human and aquatic organisms that rely on water for consumption and habitat. A mass-balance field study was conducted over two years (July 2000-May 2001) to determine the effect of nutrient source on turfgrass runoff and leachate. Treatments were arranged in an incomplete randomized block design on a slope of 7 to 9% of Arkport sandy loam (coarseloamy, mixed, active, mesic Lamellic Hapludalf) and seeded with Kentucky bluegrass (Poa pratensis L.) and perennial ryegrass (Lolium perenne L.). Three natural organic (dairy and swine compost and a biosolid) and two synthetic organic nutrient sources (readily available urea and controlled-release N source sulfur-coated urea) were applied at rates of 50 and 100 kg N ha(-1) per application (200 kg ha(-1) yr(-1)). Runoff water collected from 33 storms and composite monthly leachate samples collected with ion exchange resins were analyzed for nitrate (NO3- -N), phosphate (PO4(3-) -P), and ammonium (NH4+ -N). Nutrient concentrations and losses in both runoff and leachate were highest for the 20-wk period following turfgrass seeding. The NO3- -N and NH4+ -N losses declined significantly once turfgrass cover was established, but PO4(3-) -P levels increased in Year 2. Turf's ability to reduce nutrient runoff and leachate was related to overall plant growth and shoot density. The use of natural organics resulted in greater P loss on a percent applied P basis, while the more soluble synthetic organics resulted in greater N loss.     

Field application of farmstead runoff to vegetated filter strips: surface and subsurface water quality assessment

Farmstead runoff poses significant environmental impacts to ground and surface waters. Three vegetated filter strips were assessed for the treatment of dairy farmstead runoff at the soil surface and subsurface at 0.3- or 0. 46-m and 0. 76-m depths for numerous storm events. A medium-sized Michigan dairy was retrofitted with two filter strips on sandy loam soil and a third filter strip was implemented on a small Michigan dairy with sandy soil to collect and treat runoff from feed storage, manure storage, and other impervious farmstead areas. All filter strips were able to eliminate surface runoff via infiltration for all storm events over the duration of the study, eliminating pollutant contributions to surface water. Subsurface effluent was monitored to determine the contributing groundwater concentrations of numerous pollutants including chemical oxygen demand (COD), metals, and nitrates. Subsurface samples have an average reduction of COD concentrations of 20, 11, and 85% for the medium dairy Filter Strip 1 (FS1), medium dairy Filter Strip 2 (FS2), and the small Michigan dairy respectively, resulting in average subsurface concentrations of 355, 3960, and 718 mg L COD. Similar reductions were noted for ammonia and total Kjeldahl nitrogen (TKN) in the subsurface effluent. The small Michigan dairy was able to reduce the pollutant leachate concentrations of COD, TKN, and ammonia over a range of influent concentrations. Increased influent concentrations in the medium Michigan dairy filter strips resulted in an increase in COD, TKN, and ammonia concentrations in the leachate. Manganese was leached from the native soils at all filter strips as evidenced by the increase in manganese concentrations in the leachate. Nitrate concentrations were above standard drinking water limits (10 mg L), averaging subsurface concentrations of 11, 45, and 25 mg L NO-N for FS1, FS2, and the small Michigan dairy, respectively.     

Improving lake riparian source area management using surface and subsurface runoff indices

Sensitivity indices, which rank factors pertinent to surface and subsurface runoff pathways, were used to identify phosphorus source areas in riparian zones of 15 northern Minnesota lakes. Watershed models were first developed using a geographic information system (GIS). Empirical models were then developed correlating water quality with land use, lake morphometry, and riparian sensitivity. Base models of forested, cultivated, pasture/open, wetland and residential land use within 100, 200, 400, and 2000 m of the study lakes were regressed on total phosphorus and chlorophyll-a. Area-weighted groundwater and surface runoff sensitivity indices were then incorporated into each model and tested for significance. Within the 200-m buffer, the total phosphorus base model was improved by including the groundwater index alone. The chlorophyll-a base model at 200 m was improved by including: (1) the groundwater index alone, and (2) both the groundwater and surface runoff sensitivity indices. Results suggest that surface and subsurface runoff analysis of potential source areas can improve decision making for lake riparian management.     

Influence of alternative and conventional farming practices on subsurface drainage and water quality

Agricultural runoff contributes nutrients to nonpoint-source pollution of surface waters. This study was conducted to investigate the potential use of alternative farming practices to improve water quality. The study examined the effects of both alternative and conventional farming practices on subsurface drainage and nitrogen and phosphorus loss through subsurface drainage from glacial till soils (i.e., Calciaquolls, Endoaquolls, Eutrudepts, Hapludolls) in southwest Minnesota. Alternative farming practices included organic management practices, species biodiversity, and/or practices that include reduced inputs of synthetic fertilizer and pesticides. Conventional farming practices include corn-soybean (Zea mays L.-Glycine max L., respectively) rotations and their associated recommended fertilizer rates as well as pesticide usage. Precipitation was highly variable during the 3-yr study period including a below-average year (2003), an average year (2002), and an above-average year (2004). Results indicate that alternative farming practices reduced subsurface drainage discharge by 41% compared with conventional practices. Flow-weighted mean nitrate-nitrogen (nitrate N) concentrations during tile flow were 8.2 and 17.2 mg L(-1) under alternative and conventional farming practices, respectively. Alternative farming practices reduced nitrate N losses by between 59 and 62% in 2002 and 2004 compared with conventional practices. Ammonium-nitrogen (ammonium N), orthophosphorus, and total phosphorus losses in subsurface drainage were very low and did not pose a substantial risk of pollution. Results suggest that alternative farming practices have the potential to reduce agricultural impacts on water quality.     

Simulated wetland conservation-restoration effects on water quantity and quality at watershed scale

Wetlands are one of the most important watershed microtopographic features that affect hydrologic processes (e.g., routing) and the fate and transport of constituents (e.g., sediment and nutrients). Efforts to conserve existing wetlands and/or to restore lost wetlands require that watershed-level effects of wetlands on water quantity and water quality be quantified. Because monitoring approaches are usually cost or logistics prohibitive at watershed scale, distributed watershed models such as the Soil and Water Assessment Tool (SWAT), enhanced by the hydrologic equivalent wetland (HEW) concept developed by Wang [Wang, X., Yang, W., Melesse, A.M., 2008. Using hydrologic equivalent wetland concept within SWAT to estimate streamflow in watersheds with numerous wetlands. Trans. ASABE 51 (1), 55–72.], can be a best resort. However, there is a serious lack of information about simulated effects using this kind of integrated modeling approach. The objective of this study was to use the HEW concept in SWAT to assess effects of wetland restoration within the Broughton's Creek watershed located in southwestern Manitoba, and of wetland conservation within the upper portion of the Otter Tail River watershed located in northwestern Minnesota. The results indicated that the HEW concept allows the nonlinear functional relations between watershed processes and wetland characteristics (e.g., size and morphology) to be accurately represented in the models. The loss of the first 10–20% of the wetlands in the Minnesota study area would drastically increase the peak discharge and loadings of sediment, total phosphorus (TP), and total nitrogen (TN). On the other hand, the justifiable reductions of the peak discharge and loadings of sediment, TP, and TN in the Manitoba study area may require that 50–80% of the lost wetlands be restored. Further, the comparison between the predicted restoration and conservation effects revealed that wetland conservation seems to deserve a higher priority while both wetland conservation and restoration may be equally important.     

Nitrogen source effects on nitrous oxide emissions from irrigated no-till corn

Nitrogen fertilization is essential for optimizing crop yields; however, it may potentially increase nitrous oxide (N2O) emissions. The study objective was to assess the ability of commercially available enhanced-efficiency N fertilizers to reduce N2O emissions following their application in comparison with conventional dry granular urea and liquid urea-ammonium nitrate (UAN) fertilizers in an irrigated no-till (NT) corn (Zea mays L.) production system. Four enhanced-efficiency fertilizers were evaluated: two polymer-coated urea products (ESN and Duration III) and two fertilizers containing nitrification and urease inhibitors (SuperU and UAN+AgrotainPlus). Nitrous oxide fluxes were measured during two growing seasons using static, vented chambers and a gas chromatograph analyzer. Enhanced-efficiency fertilizers significantly reduced growing-season N2O-N emissions in comparison with urea, including UAN. SuperU and UAN+AgrotainPlus had significantly lower N2O-N emissions than UAN. Compared with urea, SuperU reduced N2O-N emissions 48%, ESN 34%, Duration III 31%, UAN 27%, and UAN+AgrotainPlus 53% averaged over 2 yr. Compared with UAN, UAN+AgrotainPlus reduced N2O emissions 35% and SuperU 29% averaged over 2 yr. The N2O-N loss as a percentage of N applied was 0.3% for urea, with all other N sources having significantly lower losses. Grain production was not reduced by the use of alternative N sources. This work shows that enhanced-efficiency N fertilizers can potentially reduce N2O-N emissions without affecting yields from irrigated NT corn systems in the semiarid central Great Plains.     

Nitrogen source effects on soil nitrous oxide emissions from strip-till corn

Nitrogen (N) application to crops generally results in increased nitrous oxide (NO) emissions. Commercially available, enhanced-efficiency N fertilizers were evaluated for their potential to reduce NO emissions from a clay loam soil compared with conventionally used granular urea and urea-ammonium nitrate (UAN) fertilizers in an irrigated strip-till (ST) corn ( L.) production system. Enhanced-efficiency N fertilizers evaluated were a controlled-release, polymer-coated urea (ESN), stabilized urea, and UAN products containing nitrification and urease inhibitors (SuperU and UAN+AgrotainPlus), and UAN containing a slow-release N source (Nfusion). Each N source was surface-band applied (202 kg N ha) at corn emergence and watered into the soil the next day. A subsurface-band ESN treatment was included. Nitrous oxide fluxes were measured during two growing seasons using static, vented chambers and a gas chromatograph analyzer. All N sources had significantly lower growing season NO emissions than granular urea, with UAN+AgrotainPlus and UAN+Nfusion having lower emissions than UAN. Similar trends were observed when expressing NO emissions on a grain yield and N uptake basis. Loss of NO-N per kilogram of N applied was <0.8% for all N sources. Corn grain yields were not different among N sources but greater than treatments with no N applied. Selection of N fertilizer source can be a mitigation practice for reducing NO emissions in strip-till, irrigated corn in semiarid areas.     

Environmental and production consequences of using alum-amended poultry litter as a nutrient source for corn

Field trials were established to compare alum-treated poultry litter (ATPL), normal poultry litter (NPL), and triple superphosphate (TSP) as fertilizer sources for corn (Zea mays L.) when applied at rates based on current litter management strategies in Virginia. Trials were established in the Costal Plain and Piedmont physiographic regions near Painter and Orange, VA, respectively. Nitrogen-based applications of ATPL or NPL applied at rates estimated to supply 173 kg of plant-available nitrogen (PAN) ha(-1) resulted in significantly lower grain yields than treatments receiving commercial fertilizer at the same rate in 2000 and 2001 at Painter. These decreases in grain yield at the N-based application rates were attributed to inadequate N availability, resulting from overestimates of PAN as demonstrated by tissue N concentrations. However, at Orange no treatment effects on grain yield were observed. Applications of ATPL did not affect Al concentrations in corn ear-leaves at either location. Exchangeable soil Al concentrations were most elevated in treatments receiving only NH4NO3 as an N source. At N-based application rates, the ATPL resulted in lower Mehlich 1-extractable P (M1-P) and water-extractable soil phosphorus (H2O-P) concentrations compared to the application of NPL. A portion of this reduction could be attributed to lower rates of P applied in the N-based ATPL treatments. Runoff collected from treatments which received ATPL 2 d before conducting rainfall simulations contained 61 to 71% less dissolved reactive phosphorus (DRP) than treatments receiving NPL. These results show that ATPL may be used as a nutrient source for corn production without significant management alterations. Alum-treated poultry litter can also reduce the environmental impact of litter applications, primarily through minimizing the P status of soils receiving long-term applications of litter and reductions in runoff DRP losses shortly after application.     

Tillage, cropping systems, and nitrogen fertilizer source effects on soil carbon sequestration and fractions

Quantification of soil carbon (C) cycling as influenced by management practices is needed for C sequestration and soil quality improvement. We evaluated the 10-yr effects of tillage, cropping system, and N source on crop residue and soil C fractions at 0- to 20-cm depth in Decatur silt loam (clayey, kaolinitic, thermic, Typic Paleudults) in northern Alabama, USA. Treatments were incomplete factorial combinations of three tillage practices (no-till [NT], mulch till [MT], and conventional till [CT]), two cropping systems (cotton [Gossypium hirsutum L.]-cotton-corn [Zea mays L.] and rye [Secale cereale L.]/cotton-rye/cotton-corn), and two N fertilization sources and rates (0 and 100 kg N ha(-1) from NH(4)NO(3) and 100 and 200 kg N ha(-1) from poultry litter). Carbon fractions were soil organic C (SOC), particulate organic C (POC), microbial biomass C (MBC), and potential C mineralization (PCM). Crop residue varied among treatments and years and total residue from 1997 to 2005 was greater in rye/cotton-rye/cotton-corn than in cotton-cotton-corn and greater with NH(4)NO(3) than with poultry litter at 100 kg N ha(-1). The SOC content at 0 to 20 cm after 10 yr was greater with poultry litter than with NH(4)NO(3) in NT and CT, resulting in a C sequestration rate of 510 kg C ha(-1) yr(-1) with poultry litter compared with -120 to 147 kg C ha(-1) yr(-1) with NH(4)NO(3). Poultry litter also increased PCM and MBC compared with NH(4)NO(3). Cropping increased SOC, POC, and PCM compared with fallow in NT. Long-term poultry litter application or continuous cropping increased soil C storage and microbial biomass and activity compared with inorganic N fertilization or fallow, indicating that these management practices can sequester C, offset atmospheric CO(2) levels, and improve soil and environmental quality.     

Fertilizer source and tillage effects on yield-scaled nitrous oxide emissions in a corn cropping system

Management practices such as fertilizer or tillage regime may affect nitrous oxide (N?O) emissions and crop yields, each of which is commonly expressed with respect to area (e.g., kg N ha or Mg grain ha). Expressing N?O emissions per unit of yield can account for both of these management impacts and might provide a useful metric for greenhouse gas inventories by relating N?O emissions to grain production rates. The objective of this study was to examine the effects of long-term (>17 yr) tillage treatments and N fertilizer source on area- and yield-scaled N?O emissions, soil N intensity, and nitrogen use efficiency for rainfed corn ( L.) in Minnesota over three growing seasons. Two different controlled-release fertilizers (CRFs) and conventional urea (CU) were surface-applied at 146 kg N ha(-1) several weeks after planting to conventional tillage (CT) and no-till (NT) treatments. Yield-scaled emissions across all treatments represented 0.4 to 1.1% of the N harvested in the grain. Both CRFs reduced soil nitrate intensity, but not N?O emissions, compared with CU. One CRF, consisting of nitrification and urease inhibitors added to urea, decreased N?O emissions compared with a polymer-coated urea (PCU). The PCU tended to have lower yields during the drier years of the study, which increased its yield-scaled N?O emissions. The overall effectiveness of CRFs compared with CU in this study may have been reduced because they were applied several weeks after corn was planted. Across all N treatments, area-scaled N?O emissions were not significantly affected by tillage. However, when expressed per unit yield of grain, grain N, or total aboveground N, N?O emissions with NT were 52, 66, and 69% greater, respectively, compared with CT. Thus, in this cropping system and climate regime, production of an equivalent amount of grain using NT would generate substantially more N?O compared with CT.     

Tillage system, application rate, and extreme event effects on herbicide losses in surface runoff

Conservation tillage can reduce soil loss; however, the residual herbicides normally used to control weeds are often detected in surface runoff at high levels, particularly if runoff-producing storms occur shortly after application. Therefore, we measured losses of alachlor, atrazine, linuron, and metribuzin from seven small (0.45-0.79-ha) watersheds for 9 yr (1993-2001) to investigate whether a reduced-input system for corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] production with light disking, cultivation, and half-rate herbicide applications could reduce losses compared with chisel and no-till. As a percentage of application, annual losses were highest for all herbicides for no-till and similar for chisel and reduced-input. Atrazine was the most frequently detected herbicide and yearly flow-weighted concentrations exceeded the drinking water standard of 3 microg L(-1) in 20 out of 27 watershed years that it was applied. Averaged for 9 corn yr, yearly flow-weighted atrazine concentrations were 26.3, 9.6, and 8.3 microg L(-1) for no-till, chisel, and reduced-input, respectively. Similarly, flow-weighted concentrations of alachlor exceeded the drinking water standard of 2 microg L(-1) in 23 out of 54 application years and in all treatments. Thus, while banding and half-rate applications as part of a reduced-input management practice reduced herbicide loss, concentrations of some herbicides may still be a concern. For all watersheds, 60 to 99% of herbicide loss was due to the five largest transport events during the 9-yr period. Thus, regardless of tillage practice, a small number of runoff events, usually shortly after herbicide application, dominated herbicide transport.     

Global and regional potential of wastewater as a water,nutrient and energy source

There is a proactive interest in recovering water, nutrients and energy from waste streams with the increase in municipal wastewater volumes and innovations in resource recovery. Based on the synthesis of wastewater data, this study provides insights into the global and regional “potential” of wastewater as water, nutrient and energy sources while acknowledging the limitations of current resource recovery opportunities and promoting efforts to fast-track high-efficiency returns. The study estimates suggest that, currently, 380 billion m³ (m³ = 1,000 L) of wastewater are produced annually across the world which is a volume five-fold the volume of water passing through Niagara Falls annually. Wastewater production globally is expected to increase by 24% by 2030 and 51% by 2050 over the current level. Among major nutrients, 16.6 Tg (Tg = million metric ton) of nitrogen are embedded in wastewater produced worldwide annually; phosphorus stands at 3.0 Tg and potassium at 6.3 Tg. The full nutrient recovery from wastewater would offset 13.4% of the global demand for these nutrients in agriculture. Beyond nutrient recovery and economic gains, there are critical environmental benefits, such as minimizing eutrophication. At the energy front, the energy embedded in wastewater would be enough to provide electricity to 158 million households. These estimates and projections are based on the maximum theoretical amounts of water, nutrients and energy that exist in the reported municipal wastewater produced worldwide annually. Supporting resource recovery from wastewater will need a step-wise approach to address a range of constraints to deliver a high rate of return in direct support of Sustainable Development Goals (SDG) 6, 7 and 12, but also other Goals, including adaptation to climate change and efforts in advancing “net-zero” energy processes towards a green economy.     

Tile water quality following liquid swine manure application into standing corn

The quality of water draining fields fertilized with liquid swine (Sus scrofa) manure (LSM) sidedressed into standing corn (Zea mays L.) at rates ranging from 0 to 94 m(3) ha(-1), either topdressed (TD) onto the surface, or injected (INJ) into the soil once annually for each of three consecutive years was evaluated. Liquid swine manure application rate was a critical driver of preferential flow of LSM to tile as detected by turbidity, concentrations of NH(4)(+)-N, dissolved reactive phosphorus (DRP), and the presence of enteric bacteria (Escherichia coli). Contaminant movement to drains occurred immediately after 75 and 94 m(3) LSM ha(-1) were injected (e.g., 2.5 mg DRP L(-1), 3-yr average). With injection of 56 m(3) ha(-1) or less, drainage water was not turbid and concentrations of NH(4)(+)-N, DRP, and enteric bacteria were dramatically lower than with the higher rates, even when tiles flowed freely during manure application. Application method also affected tile water quality. With TD applications (37 and 56 m(3) ha(-1)), nutrients and bacteria did not move to tiles at the time of application, but with rains that fell within 3 d after application, concentrations increased (e.g., 0.1 mg DRP L(-1)), although less than with INJ. Overall, sidedress injection rates that supplied adequate crop nutrients did not compromise drainage water quality.     

The acetochlor registration partnership surface water monitoring program for four corn herbicides

A surface drinking water monitoring program for four corn (Zea mays L.) herbicides was conducted during 1995-2001. Stratified random sampling was used to select 175 community water systems (CWSs) within a 12-state area, with an emphasis on the most vulnerable sites, based on corn intensity and watershed size. Finished drinking water was monitored at all sites, and raw water was monitored at many sites using activated carbon, which was shown capable of removing herbicides and their degradates from drinking water. Samples were collected biweekly from mid-March through the end of August, and twice during the off-season. The analytical method had a detection limit of 0.05 microg L(-1) for alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)-acetamide] and 0.03 microg L(-1) for acetochlor [2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl)-acetamide], atrazine [6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine], and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)-acetamide]. Of the 16528 drinking water samples analyzed, acetochlor, alachlor, atrazine, and metolachlor were detected in 19, 7, 87, and 53% of the samples, respectively. During 1999-2001, samples were also analyzed for the presence of six major degradates of the chloroacetanilide herbicides, which were detected more frequently than their parent compounds, despite having higher detection limits of 0.1 to 0.2 microg L(-1). Overall detection frequencies were correlated with product use and environmental fate characteristics. Reservoirs were particularly vulnerable to atrazine, which exceeded its 3 microg L(-1) maximum contaminant level at 25 such sites during 1995-1999. Acetochlor annualized mean concentrations (AMCs) did not exceed its mitigation trigger (2 microg L(-1)) at any site, and comparisons of observed levels with standard measures of human and ecological hazards indicate that it poses no significant risk to human health or the environment.     

Long-term effects of sustained beef feedlot manure application on soil nutrients, corn silage yield, and nutrient uptake

A field study was initiated in 1992 to investigate the long-term impacts of beef feedlot manure application (composted and uncomposted) on nutrient accumulation and movement in soil, corn silage yield, and nutrient uptake. Two application strategies were compared: providing the annual crop nitrogen (N) requirement (N-based rate) or crop phosphorus (P) removal (P-based rate), as well as a comparison to inorganic fertilizer. Additionally, effects of a winter cover crop were evaluated. Irrigated corn (Zea mays L.) was produced annually from 1993 through 2002. Average silage yield and crop nutrient removal were highest with N-based manure treatments, intermediate with P-based manure treatments, and least with inorganic N fertilizer. Use of a winter cover crop resulted in silage yield reductions in four of ten years, most likely due to soil moisture depletion in the spring by the cover crop. However, the cover crop did significantly reduce NO3-N accumulation in the shallow vadose zone, particularly in latter years of the study. The composted manure N-based treatment resulted in significantly greater soil profile NO3-N concentration and higher soil P concentration near the soil surface. The accounting procedure used to calculate N-based treatment application rates resulted in acceptable soil profile NO3-N concentrations over the short term. While repeated annual manure application to supply the total crop N requirement may be acceptable for this soil for several years, sustained application over many years carries the risk of unacceptable soil P concentrations.     

Modeling the relationship between land use and surface water quality

It is widely known that watershed hydrology is dependent on many factors, including land use, climate, and soil conditions. But the relative impacts of different types of land use on the surface water are yet to be ascertained and quantified. This research attempted to use a comprehensive approach to examine the hydrologic effects of land use at both a regional and a local scale. Statistical and spatial analyses were employed to examine the statistical and spatial relationships of land use and the flow and water quality in receiving waters on a regional scale in the State of Ohio. Besides, a widely accepted watershed-based water quality assessment tool, the Better Assessment Science Integrating Point and Nonpoint Sources (BASINS), was adopted to model the plausible effects of land use on water quality in a local watershed in the East Fork Little Miami River Basin. The results from the statistical analyses revealed that there was a significant relationship between land use and in-stream water quality, especially for nitrogen, phosphorus and Fecal coliform. The geographic information systems (GIS) spatial analyses identified the watersheds that have high levels of contaminants and percentages of agricultural and urban lands. Furthermore, the hydrologic and water quality modeling showed that agricultural and impervious urban lands produced a much higher level of nitrogen and phosphorus than other land surfaces. From this research, it seems that the approach adopted in this study is comprehensive, covering both the regional and local scales. It also reveals that BASINS is a very useful and reliable tool, capable of characterizing the flow and water quality conditions for the study area under different watershed scales. With little modification, these models should be able to adapt to other watersheds or to simulate other contaminants. They also can be used to study the plausible impacts of global environmental change. In addition, the information on the hydrologic effects of land use is very useful. It can provide guidelines not only for resource managers in restoring our aquatic ecosystems, but also for local planners in devising viable and ecologically-sound watershed development plans, as well as for policy makers in evaluating alternate land management decisions.     

Impacts of a nutrient trading plan on stream water quality in Sugar Creek,Ohio

In the early 2000s, a phosphorus nutrient trading plan (NTP) requiring best management practices (BMPs) to be installed as pollution abatement strategies to offset phosphorus waste from the Alpine Cheese Company was implemented in four subwatersheds of Sugar Creek in northeast Ohio. To assess the impacts of the Alpine NTP, 49 sites were sampled approximately biweekly from 2010 to 2018 for phosphate, total phosphorus, nitrate, ammonia, and total nitrogen. In addition, the Ohio Environmental Protection Agency conducted stream health surveys at 21 sites before and after the BMPs were implemented. This study evaluated the potential impact of 68 BMPs implemented under the NTP on the observed changes in nutrient concentrations and stream health indicators. Most nutrient concentrations observed during high discharge conditions showed significant declines from 2010 to 2018 for all subwatersheds, which was most likely due to BMPs that reduced erosion and surface runoff. However, there were fewer significant declines and some significant increases in nutrient levels during low discharge conditions, suggesting a possible contribution from legacy nutrient sources. Most sites reported increases in stream health indicators, but many streams are still below recommended levels. Collectively, the installation of BMPs and decreases in nutrient concentrations observed during high discharge conditions can be attributed to the NTP and likely contributed to improved stream health.     

Influence of nutrient levels on uptake and effects of mercury, cadmium, and lead in water spinach

In Southeast Asia the aquatic macrophyte water spinach (Ipomoea aquatica Forsk.) is a popular vegetable that is cultivated in freshwater courses. These often serve as recipients for domestic and other sorts of wastewater that often contain a variety of pollutants, such as heavy metals. In addition, fertilizers are frequently used where water spinach is cultivated commercially for the food market. To estimate the importance of ambient nutrient concentrations for accumulation of mercury (Hg), cadmium (Cd), and lead (Pb) in water spinach, plants were exposed to nutrient solutions of different strength and with varying metal concentrations. Metal-induced toxic effects, which might possibly affect the yield of the plants, were also studied. The lower the nutrient strength in the medium was, the higher the metal concentrations that accumulated in the different plant parts and the lower the metal concentration in the medium at which metal-induced toxic effects occurred. Accordingly, internal metal concentrations in the plants were correlated to toxic effects. Plants exposed to metals retained a major proportion of the metals in the roots, which had a higher tolerance than shoots for high internal metal concentrations.