NO3-N Concentrations in Shallow and Deep Groundwater Wells from 1991 to 2003

Nitrates from fertilizers and manure application have been detected in the surface and groundwater in many agricultural regions of the country including Iowa. The current practices of fertilizer application methods and rates are believed to be contributing significantly in the contamination of groundwater. Therefore, it is imperative that tillage and planting systems, regarded as best management practices for agricultural sustainability, minimize the potential for chemical runoff and leaching losses into groundwater with alternative chemical management systems. If the potential for contamination is not reduced by developing and successfully demonstrating the innovative nitrogen management practices, additional regulations could be the result

Impacts of Nitrogen Management Systems on Water Quality

Objectives of the Study: To determine the impacts on water quality of recommended application rates of swine manure, based on nitrogen uptake requirements of crops. To study the long-term effects of over-application of swine manure on nitrogen leaching to groundwater. To study the long-term effects of spring and fall injection methods of swine manure application on crop yields, and nitrogen, in surface runoff and shallow groundwater. To develop and recommend appropriate manure and nutrient management practices to reduce the water contamination potential from manure and UAN applications and enhance the use of swine manure as an alternative to the use of inorganic fertilizers for Iowa's sustainable agriculture. </ol

Collection and Monitoring of One-meter Cubic Soil Monoliths for Leaching Systems

This report presents methodology for excavating one-meter cubic undisturbed soil monoliths for detailed laboratory investigations of solute transport through the soil profile. Eight soil monoliths were collected in 1992 from three field areas that had been under consistent tillage systems since 1978. The soil was predominantly a Kenyon silt loam (Typic Hapludoll) with the water table maintained by subsurface drainage. Each monolith was instrumented with time-domain reflectometer (TDR) waveguides, and mini-tensiometers to monitor changes in soil water content and soil matric potential on three sides. A rainfall simulator was constructed to apply water at a rainfall intensity of 33 mm-h–1 to a 0.8 m × 0.8 m surface area of the monolith. A conservative tracer (KBr) was applied to the soil surface and leachate samples were collected from 36 locations at the bottom of each monolith using fiberglass wick extractors attached to 810 mm2 areas in a 6 ×6 grid arrangement. Water application, soil water content and leachate were monitored to determine how surface tillage affected preferential flow.Results suggest that the soil monolith collection and transportation procedures maintained the integrity of the soil profile. Anion tracers provided an inexpensive means of simulating different nitrogen application methods. Grid cell samplers using fiberglass wicks allowed analysis of the spatial variation in leaching losses. Leachate samples provided information about the potential impact of nitrogen application method on leaching losses. When coupled with time domain reflectometry and mini-tensiometers, electronic data logging equipment can be used to monitor changes in soil volumetric water content and matric potential

Hydraulic Performance of the Denitrification Bioreactor

Denitrification bioreactors, also known as woodchip bioreactors, are a new strategy for improving drainage water quality before these flows arrive at local streams, rivers, and lakes. A bioreactor is an excavated, woodchip-filled pit that is capable of supporting native microbes that convert nitrate in the drainage water to nitrogen gas. The idea of these edgeof-field treatment systems is still relatively new, meaning it is important for investigations to be made into how to design these “pits” and to determine how drainage water moves through the woodchips. Because the bioreactor at the ISU Northeast Research Farm (NERF) is one of the best monitored bioreactor sites in the state, it provided an ideal location to not only monitor bioreactor nitrate-reduction performance, but also to investigate design hydraulics

The Use of the Soil-Plant-Air-Water Model to Predict the Hydraulic Performance of Vegetative Treatment Areas for Controlling Open Feedlot Runoff

Several Iowa beef feedlots have interim, National Pollution Discharge Elimination System (NPDES) permits for vegetative treatment systems (VTS) to control and treat feedlot runoff. In Iowa, performance of these systems is predicted for permitting purposes using either the Iowa State University-Vegetated Treatment Area (ISU-VTA) Model or the Iowa State University -Vegetated Infiltration Basin/Vegetated Treatment Area (ISU-VIB/VTA) Model. For an Iowa NPDES permit, these systems must be shown through modeling to have equal or better performance than a conventional runoff containment basin on the basis of median nutrient mass released over 25 years. Modeling is also a useful design tool for both Concentrated Animal Feeding Operations (CAFOs) and non-CAFO sized operations wishing to utilize VTS systems. Field-scale VTS performance monitoring conducted over the past two years by ISU has shown that the current ISU models do not accurately predict actual hydraulic performance at the monitored VTSs. The ISU models are being revised to improve their performance. Along with improving the ISU-VTS model performance, other modeling alternatives are being investigated. The Soil-Plant-Air-Water (SPAW) model is one possible alternative for modeling the hydraulic performance of a VTA. For this paper, the SPAW predicted performance was compared to monitoring results at four VTAs located in Iowa. Two different methods were used to model the VTA performance, the first method utilized the field module of SPAW; this method was found to have Nash-Sutcliffe modeling efficiencies ranging from 0.16 to 0.57. At all locations, the SPAW model underestimated the amount of release that occurred from the VTAs. The second modeling method utilized the pond module of SPAW, for this method the Nash-Sutcliffe modeling efficiencies ranged from 0.26 to 0.83. Again, the SPAW model underestimated the cumulative volume of effluent released from the VTAs

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

Impact of Drainage Water Management on Crop Yield

The objectives of this project were to study nitrate loading in subsurface drainage and corn-soybean yield response under various drainage water management practices. This experiment explores various drainage strategies to reduce nitrate loading to surface waters in southeast Iowa

Role of Directly Connected Macropores on Pathogen Transport to Subsurface Drainage Water

Pathogen contamination of water supplies is now considered one of the top water quality issues in the United States and worldwide. Continual application of livestock manure may contribute to nonpoint source pollution by releasing microbial pathogens including bacteria, virus, and protozoa, through runoff and subsurface drainage water to surface and ground water. Many studies have been conducted in the laboratories and fields to understand the preferential flow through macropores. But no experiments in the field have been conducted to examine the breakthrough curve of pathogen and/or Escherichia coliform (E.coli) with directly connected macropores. The objective of this research is to address the transport of pathogens (specifically the indicator organism E. coli) through soils, and more specifically the role of macropores in the transport of E. coli to subsurface drains. A greater understanding and more theoretical modeling approach is needed to understand the role of directly connected macropores on pathogen transport to subsurface drainage

Impact of Liquid Swine Manure Application and Cover Crops on Nitrate in Subsurface Drainage Water

The primary objective of this project was to determine the impact of appropriate rates of swine manure applications to corn and soybeans based on nitrogen requirements of crops and the potential of nitrate leaching to groundwater. Another purpose of this longterm experimental study was to develop and recommend appropriate manure and nutrient management practices to producers to minimize the water contamination potential and enhance the use of swine manure as an organic fertilizer. A third component of this study was to determine the potential effects of rye as a cover crop to reduce nitrate loss to shallow ground water

Impact of Liquid Swine Manure Application and Cover Crops on Ground Water Quality

The primary design ofthis project isto determine the impact of appropriate rates of swine manure applications to corn and soybeans based on nitrogen and phosphorus requirements, crop yields, soil phosphorus accumulation, and nitrate and phosphorus leaching to groundwater. Another purpose of this design is to develop and recommend appropriate manure and nutrient management practices to producers to minimize the water contamination potential and enhance the use of swine manure as an organic fertilizer. A third component is to determine the potential effects of rye as a cover crop to reduce nitrate loss to shallow ground water