Reducing Nitrate-N Losses to Achieve Water Quality Goals

Nutrient losses from agricultural systems in the Mississippi River basin have contributed to the hypoxic zone in the Gulf of Mexico. In 2008, in response to this challenge, the U.S. EPA‘s Hypoxia Task Force released an action plan for a national strategy to reduce, mitigate, and control hypoxia in the northern Gulf of Mexico and improve water quality in the Mississippi River basin (www.epa.gov/ms-htf). The action plan indicated that significant (i.e., 45%) reductions in riverine nitrogen and phosphorus loads are needed to achieve the goal of reducing the size of the hypoxic zone, and improve water quality in the basin. One of the main items in the 2008 action plan was the call for state-level nutrient reduction strategies. As a result, the twelve states bordering the Mississippi and Ohio Rivers have developed and begun implementing comprehensive nutrient reduction strategies (www.epa.gov/ms-htf/hypoxia-taskforce-nutrient-reduction-strategies). Iowa was one of the first states to conduct a scientific assessment of the potential nutrient reduction of different agricultural management practices and the level of implementation that might be needed to reach the goal of 45% reduction (www.nutrientstrategy.iastate.edu)

Impact of application rate and timing on nitrate-nitrogen loss through subsurface drainage systems

Subsurface agricultural drainage has allowed for enhanced agricultural production in many areas of the world including the upper Midwest, United States. However, the presence of nitrate-nitrogen (nitrate-N) in subsurface drain water is a topic of intense scrutiny. Many studies have been done looking at ways to reduce nitrate-N in tile drainage (Baker et al., 1975; Baker and Johnson, 1981; Hanway and Laflen, 1974; Kanwar et al., 1988).With the growing concern for the health of the Gulf of Mexico (Mitsch et al., 2001; Rabalais et al., 1996), there is still a need to study and recommend nitrogen management practices that have the potential to reduce nitrate-N concentrations and loss through subsurface drainage systems. One practice is to apply the appropriate amount of nitrogen and previous work has found a relationship between nitrogen application rate and drain nitrate-N concentration showing. Another commonly discussed practice is to apply nitrogen in the spring as close to the time that the corn crop needs nitrogen as possible. The objectives of this study were to evaluate timing and rate of nitrogen application on nitrate-N leaching and crop yield

Technical Note: Hydraulic Property Determination of Denitrifying Bioreactor Fill Media

Denitrification bioreactors are one of the newest options for nitrate removal in agricultural drainage waters. Optimization of denitrification bioreactor design requires the ability to identify concrete values for the hydraulic properties of bioreactor fill media. Hydraulic properties, chiefly saturated hydraulic conductivity but also porosity and particle size, are not known for many types of possible bioreactor media though they have a significant impact upon bioreactor design and performance. This work was undertaken to more fully quantify the hydraulic properties of the major type of fill media used in Iowa denitrification bioreactors through a series of porosity, hydraulic conductivity, and particle size analysis tests. In addition, a particle size analysis was performed for two types of woodchips and one type of wood shreds in order to quantify and highlight the differences between what is commonly referred to as wood fill. Saturated hydraulic conductivity was determined for blends of woodchips, corn cobs, and pea gravel. For one of the most common types of woodchips used in bioreactors, the porosity varied from 66% to 78% depending on packing density and the average saturated hydraulic conductivity was 9.5 cm/s. It was found that additions of pea gravel significantly increased the hydraulic conductivity of woodchips though additions of corn cobs did not. Regardless of the fill mixture used, it is vital to design the bioreactor using the hydraulic properties for that specific media

Nitrate loss in subsurface drainage as affected by nitrogen application rate and timing under a cornsoybean rotation system

Subsurface agricultural drainage has allowed for enhanced crop production in many areas of the world including the upper Midwest, United States. However, the presence of nitrate-nitrogen (nitrate-N) in subsurface tile drainage water is a topic of intense scrutiny due to several water quality issues. Many studies have been conducted looking at ways to reduce nitrate-N in tile drainage (Baker et al., 1975; Baker and Johnson, 1981; Hanway and Laflen, 1974; Kanwar et al., 1988).With the growing concern for the health of the Gulf of Mexico (Mitsch et al., 2001; Rabalais et al., 1996) and local water quality concerns, there is a need to understand how recommended nitrogen management practices, such as through nitrogen rate and timing, impact nitrate-N concentrations from subsurface drainage systems. The objective of this paper is to summarize results of studies from within Iowa and nearby states that have documented the impact of nitrogen application rate and timing on tile drainage nitrate loss

Impact of Fertilizer Application Timing on Drainage Nitrate Levels

Nitrate loss from drainage systems in Iowa and other upper Midwestern states is a concern relative to local water supplies as well as the hypoxic zone in the Gulf of Mexico. As a result, there is a need to quantify how various nitrogen management practices impact nitrate loss. One practice that is commonly mentioned as a potential strategy to reduce nitrate loss is to vary fertilizer application timing and specifically apply nitrogen as close to when the growing crop needs it as possible. At a site in Gilmore City, Iowa, a number of fertilizer timing and rate schemes within a corn soybean rotation were used to study the impacts on nitrate leaching. Timing schemes include nitrogen application in the fall and an early season sidedress in the spring with each scheme having four replicates for both corn and soybeans. Fertilizer application rates investigated are 84 and 140 kg/ha (75 and 125 lb/ac) in the fall and 84 and 140 kg/ha (75 and 125 lb/ac) in the spring. The timing and rates have been practiced since 2005 with contrasting weather conditions each year. Overall, an annual basis there was not significant differences in nitrate concentrations or loss exiting the drainage system between the application rates or between the fall and spring application. In addition, there was not a yield penalty to the corn crop when fertilizer as applied in the fall versus the spring

Impacts of Crop, Biomass Harvest Systems, and Nutrient Management on Yield and Subsurface Drainage Water Quality

Grain-crop biomass and perennial grass biomass are of particular interest for their use in bioenergy production systems. Nutrient needs, particularly nitrogen and phosphorus, change with varying cropping systems, harvest systems, and rates of fertilizer application. Furthermore, manure generated from livestock production can be a viable nutrient source for cropping systems, reducing the need for commercial fertilizers. The primary focus of this study was to investigate nutrient loss, primarily nitrate-nitrogen loss, in subsurface drainage water under a variety of cropping, nutrient management, and harvest scenarios. Overall crop yields and biomass production were also evaluated

Water and Nutrient Research: In-field and Offsite Strategies—2008 Annual Report

Much of Iowa is characterized by relatively flat, poorly-drained soils which, with extensive artificial subsurface drainage, have became some of the most valuable, productive lands in the State. In 2002, the average land value for the 22-county area making up most of the Des Moines Lobe was $2,436 an acre, and 80.5% of that area was in row-crops (42.9% in corn and 37.6% soybeans). However, this drained land has also become a source of significant NO3 loss because of the changes in land-use and hydrology brought about by tile drainage. While surface runoff is decreased with subsurface drainage (resulting in decreased losses of sediment, ammoniumnitrogen, phosphorus, pesticides and micro-organisms), subsurface flow and leaching losses of NO3 are increased. This is due mostly to an increase in volume and the “short-circuiting” of subsurface flow, but also in part to the increased aeration of organic-rich soils with potentially increased mineralization and formation of NO3 (and less denitrification) in the soil profile. The problem of excess nutrient loads can probably be ameliorated by a combination of in field and off site practices, but the limitations and appropriateness of alternative practices must be understood and outcomes must be measurable. Promising in field practices include nutrient management, drainage management, and alternative cropping systems. Nitrate-removal wetlands are a proven edge-of-field practice for reducing nitrate loads to downstream water bodies and are a particularly promising approach in tile drained landscapes. Strategies are needed that can achieve measurable and predictable reductions in the export of nutrients from tile drained landscapes. The principal objectives of this project are (1) to evaluate the performance of nutrient management, drainage management, and alternative cropping systems with respect to profitability and export of water and nutrients (nitrate-nitrogen and total phosphorus) from tile drained systems and (2) to evaluate the performance of nitrate-removal wetlands in reducing nitrate export from tile drained systems. This annual report describes activities related to objectives 1 and 2 along with outreach activities that were directly related to this project. For objective 1, crop years 2005, 2006, and 2007 are presented. Also, outreach activities are noted for 2005, 2006, and 2007 to provide an overall project summary

A novel approach for organelle-specific DNA damage targeting reveals different susceptibility of mitochondrial DNA to the anticancer drugs camptothecin and topotecan

DNA is susceptible of being damaged by chemicals, UV light or gamma irradiation. Nuclear DNA damage invokes both a checkpoint and a repair response. By contrast, little is known about the cellular response to mitochondrial DNA damage. We designed an experimental system that allows organelle-specific DNA damage targeting in Saccharomyces cerevisiae. DNA damage is mediated by a toxic topoisomerase I allele which leads to the formation of persistent DNA single-strand breaks. We show that organelle-specific targeting of a toxic topoisomerase I to either the nucleus or mitochondria leads to nuclear DNA damage and cell death or to loss of mitochondrial DNA and formation of respiration-deficient ‘petite’ cells, respectively. In wild-type cells, toxic topoisomerase I–DNA intermediates are formed as a consequence of topoisomerase I interaction with camptothecin-based anticancer drugs. We reasoned that targeting of topoisomerase I to the mitochondria of top1Δ cells should lead to petite formation in the presence of camptothecin. Interestingly, camptothecin failed to generate petite; however, its derivative topotecan accumulates in mitochondria and induces petite formation. Our findings demonstrate that drug modifications can lead to organelle-specific DNA damage and thus opens new perspectives on the role of mitochondrial DNA-damage in cancer treatment

Health profiles of 996 melanoma survivors: the M. D. Anderson experience

BACKGROUND: The incidence and survival of melanoma are increasing, but little is known about its long-term health effects in adult survivors. METHODS: A health survey was available from 996 melanoma survivors (577 treated with surgery alone, and 391 with combined treatments). Their medical/physiologic and psychosocial responses were analyzed and compared with those of the survivors from other cancers. RESULTS: The melanoma survivors were 44.8 ± 12.8 years of age at diagnosis (significantly younger than the survivors of other cancers) and 63.7 ± 12.8 years at survey. Melanoma survivors were less likely to report that cancer had affected their health than survivors of other cancers (15.8% vs. 34.9%). The 577 individuals treated with surgery alone reported arthritis/osteoporosis, cataracts, and heart problems most frequently (less often than survivors of other cancers). The 391 individuals who had undergone combined treatments reported circulation problems and kidney problems generally as often as survivors of other cancers. Health problems were not associated with number of decades since diagnosis but with age at diagnosis, treatment modality, and family relationships. CONCLUSION: We present information from a large cohort of long-term survivors of melanoma. As a group, they were less likely to report that cancer had affected their overall health than survivors of other cancers; a number of disease related and psychosocial factors appear to influence their health profiles

Neutron Scattering Studies of spin excitations in hole-doped Ba0.67K0.33Fe2As2 superconductor

We report inelastic neutron scattering experiments on single crystals of superconducting Ba0.67K0.33Fe2As2 (Tc = 38 K). In addition to confirming the resonance previously found in powder samples, we find that spin excitations in the normal state form longitudinally elongated ellipses along the QAFM direction in momentum space, consistent with density functional theory predictions. On cooling below Tc, while the resonance preserves its momentum anisotropy as expected, spin excitations at energies below the resonance become essentially isotropic in the in-plane momentum space and dramatically increase their correlation length. These results suggest that the superconducting gap structures in Ba0.67Ka0.33Fe2As2 are more complicated than those suggested from angle resolved photoemission experiments