Recent EU legislation is directed to reverse the upward trends in the concentrations of agricultural pollutants in groundwater. However, uncertainty of the groundwater travel time towards the screens of the groundwater quality monitoring networks complicates the demonstration of trend reversal. We investigated whether trend reversal can be demonstrated by relating concentrations of pollutants in groundwater to the time of recharge, instead of the time of sampling. To do so, we used the travel time to monitoring screens in sandy agricultural areas in the Netherlands, determined by 3H/3He groundwater dating. We observed that concentrations of conservative pollutants increased in groundwater recharged before 1985 and decreased after 1990. Thereby, we demonstrated trend reversal of groundwater quality. From this research we concluded that 3H/3He dating can be used to facilitate (re)interpretation of existing groundwater quality data. The presented approach is widely applicable in areas with unconsolidated granular aquifers and large agricultural pressures on groundwater resources. Groundwater age dating reveals trends and trend reversal in groundwater quality.

The beneficial uptake of nutrients by wetland plants is countered to some extent by nutrient release back into the aquatic environment due to vegetative die-back. This current study examined whether Leersia oryzoides, a common wetland plant, exhibits luxury uptake of nutrients from simulated farm runoff. The study also tested whether with subsequent decomposition, these nutrients are released back into the water column. When exposed to elevated (>2 mg/L N and P) runoff, L. oryzoides assimilated significantly higher concentrations of nitrogen (p < 0.001) and phosphorus (p < 0.001) in above-ground biomass as compared to non-enriched treatments (<0.05 mg/L N and P). Subsequently, senescence of enriched above-ground biomass yielded significantly higher concentrations of phosphorus (2.19 ± 0.84 mg P/L). Using L. oryzoides as our model, this study demonstrates nitrogen and phosphorus sequestration during the growing season and release of phosphorus in the winter. Release of sequestered nutrients during plant senescence.

Since the beginning of the 19th century humans have increasingly fixed atmospheric nitrogen as ammonia to be used as fertilizer. The fertilizers are necessary to create amino acids and carbohydrates in plants to feed animals and humans. The efficiency with which the fertilizers eventually reach humans is very small: 5-15%, with much of the remainder lost to the environment. The global industrial production of ammonia amounts to 117 Mton NH3-N year-1 (for 2004). By comparison, we calculate that anthropogenic emissions of NH3 to the atmosphere over the lifecycle of industrial NH3 in agriculture are 45.3 Mton NH3-N year-1, about half the industrial production. Once emitted ammonia has a central role in many environmental issues. We expect an increase in fertilizer use through increasing demands for food and biofuels as population increases. Therefore, management of ammonia or abatement is necessary. Half of industrial ammonia production is eventually lost to the global environment with significant effects.

Soybean [Glycine max (L.) Merr.] cultivars Essex and Forrest that exhibit differences in ozone (O3) sensitivity were used in greenhouse experiments to investigate the role of leaf extracellular antioxidants in O3 injury responses. Charcoal-filtered air and elevated O3 conditions were used to assess genetic, leaf age, and O3 effects. In both cultivars, the extracellular ascorbate pool consisted of 80e98% dehydroascorbic acid, the oxidized form of ascorbic acid (AA) that is not an antioxidant. For all combinations of genotype and O3 treatments, extracellular AA levels were low (1e30 nmol g 1 FW) and represented 3e30% of the total antioxidant capacity. Total extracellular antioxidant capacity was twofold greater in Essex compared with Forrest, consistent with greater O3 tolerance of Essex. The results suggest that extracellular antioxidant metabolites in addition to ascorbate contribute to detoxification of O3 in soybean leaves and possibly affect plant sensitivity to O3 injury.

Agriculture is a source for three primary greenhouse gases (GHGs): CO2, CH4, and N2O. It can also be a sink for CO2 through C sequestration into biomass products and soil organic matter. We summarized the literature on GHG emissions and C sequestration, providing a perspective on how agriculture can reduce its GHG burden and how it can help to mitigate GHG emissions through conservation measures. Impacts of agricultural practices and systems on GHG emission are reviewed and potential trade-offs among potential mitigation options are discussed. Conservation practices that help prevent soil erosion, may also sequester soil C and enhance CH4 consumption. Managing N to match crop needs can reduce N2O emission and avoid adverse impacts on water quality. Manipulating animal diet and manure management can reduce CH4 and N2O emission from animal agriculture. All segments of agriculture have management options that can reduce agriculture's environmental footprint. Management options can be used to reduce agriculture's environmental impacts.

The monitoring of a spring and seven piezometers in the 3 km2 Brévilles agricultural catchment (France) over five and a half years revealed considerable spatial and temporal variability in the concentrations of atrazine and its metabolite deethylatrazine (both systematically quantified at the outlet spring): maximum 0.97 and 2.72 μg L-1, mean 0.19 and 0.59 μg L-1, respectively. Isoproturon, the pesticide applied in the greatest amount, was detected in only 10 of the 133 samples. These observations can only partly be explained by land use and intrinsic pesticide properties. Geochemical measurements and tritium dating showed the importance of the stratification of the sandy saturated zone and the buffer function of the unsaturated limestone. Principal component analysis on 39 monthly data series of atrazine, deethylatrazine, nitrate, chloride and piezometric levels revealed a temporal structuring of the data possibly reflecting the existence within the aquifer of two different reservoirs with time-variable contributions. We present an integrated approach combining geochemistry and hydrogeology that leads to a better understanding of the spatial and temporal fluctuations of the pesticide concentrations in groundwater of a pilot agricultural catchment.

Phytoremediation is potentially effective for managing excessive selenium (Se) in drainage sediment residing in the San Luis Drain in central California. This 2-year field study examined the feasibility of amending drainage sediment (containing 4.78 mg Se g 1) with methionine and casein to enhance volatilization without or with vegetation of Sporobolus airoides. Results show that without organic amendments, rates of Se volatilization were less than 25 mgm 2 d 1 in all plots. After amending the sediment with 71.4 mg methionine kg 1 soil, Se volatilization rates were 434 107 mgm 2 d 1 in vegetated plots and 289 117 mgm 2 d 1 in irrigated bare plots.With the amendment of 572 mg casein kg 1 soil, rates increased to 346 103 mgm 2 d 1 in irrigated bare plots and to 114 55 mgm 2 d 1 in vegetated plots. Both methionine and casein promoted biological remediation of Se via volatilization most effectively during the warmest months.

Nitrogen (N) budget was estimated with dissolved inorganic N (DIN) and dissolved organic N (DON) in a forested mountainous watershed in Tsukui, Kanagawa Prefecture, about 50 km west of Tokyo in Central Japan. The forest vegetation in the watershed was dominant by Konara oak (Quercus serrata) and Korean hornbeam (Carpinus tschonoskii), and Japanese cedar (Cryptomeria japonica). Nitrate (NO₃ -) concentration in the watershed streamwater was averagely high (98.0 ±± 19 (±± SD, n = 36) μmol L-¹) during 2001-2003. There was no seasonal and annual changes in the stream NO- ₃ concentration even though the highest N uptake rate presumably occurred during the spring of plant growing season, a fact indicating that N availability was in excess of biotic demands. The DON deposition rates (DON input rates) in open area and forest area were estimated as one of the main N sources, accounting for about 32% of total dissolved N (TDN). It was estimated that a part of the DON input rate contributed to the excessive stream NO- ₃ output rate under the condition of the rapid mineralization and nitrification rates, which annual DON deposition rates were positively correlated with the stream NO₃ - output rates. The DON retention rate in the DON budget had a potential capacity, which contributed to the excessive stream NO- ₃ output rate without other N contributions (e.g. forest floor N or soil N).

Global expansion and intensification of industrialized agriculture during the last 50 years was facilitated by the replacement of labor by imported chemicals and energy, thus changing the economics and the social fabric of rural communities as well as impairing water, air, and soil resources essential to sustaining food and fiber production in a world with an increasing appetite. To effectively understand and solve complex problems resulting from this agricultural revolution, expanded communications are needed at a variety of levels. It is critical for the technical community to communicate through greater interdisciplinary research among agronomists, soil scientists, hydrologists, ecologists, and others to reduce diffuse pollution from agriculture. Also, more effective translations of technical problems and solutions are needed to influence policy. Accurate advice is needed in spite of the uncertainties that scientists too often use to obscure useful information. Education will be needed for producers and conservationists to gain confidence that promised environmental responses will occur if solutions are to be implemented at more than experimental or demonstration scales. The search for comprehensive solutions to environmental degradation will require understanding the ultimate causes of pollution, not just the proximal causes. The ultimate causes will only be found by examining the systems that facilitate the release of contaminants to the environment such as the wholesale landscape changes that replaced grazing land with annual crops leading to increased leaching and runoff. Research and demonstration projects increasingly need collaborations among agronomists, livestock scientists, soil scientists, hydrologists, economists, sociologists and others who have a stake in the study of diffuse pollution and the outcomes of any proposed solutions. Partnerships developed at the working level where basic principles can be shared will help avoid the pursuit of impractical solutions when viewed from different perspectives.