Livestock grazing in the Midwestern United States can result in significant levels of runoff sediment and nutrient losses to surface water resources. Some of these contaminants can increase stream eutrophication and are suspected of contributing to hypoxic conditions in the Gulf of Mexico. This research quantified effects of livestock grazing management practices and vegetative filter strip buffers on runoff depth and mass losses of total solids, nitrate-nitrogen (NO 3 -N), and ortho-phosphorus (PO 4 -P) under natural hydrologic conditions. Runoff data were collected from 12 rainfall events during 2001 to 2003 at an Iowa State University research farm in central Iowa, United States. Three vegetative buffers (paddock area:vegetative buffer area ratios of 1:0.2, 1:0.1, and 1:0 no buffer [control]) and three grazing management practices (continuous, rotational, and no grazing [control]) comprised nine treatment combinations (vegetative buffer ratio/grazing management practice) replicated in three 1.35 ha (3.34 ac) plot areas. The total 4.05 ha (10.02 ac) study area also included nine 0.4 ha (1.0 ac) paddocks and 27 vegetative buffer runoff collection units distributed in a randomized complete block design. The study site was established on uneven terrain with a maximum of 15% slopes and We speculate this shift to significantly higher runoff and contaminant losses from no grazing treatment combination plots during 2003 reflects the variability inherent to a complex and dynamic soil-water environment of livestock grazing areas. However, we also hypothesize the environmental conditions that largely consisted of a dense perennial cool-season grass type, high-relief landscape, and relatively high total rainfall depth may not necessarily include livestock grazing activities. (Downing et al. 2000;James et al. 2007) and have higher P losses than ungrazed pastures (Gillingham and Thorrold 2000). Nitrogen (N) losses from agricultural/grazing fields to surface and subsurface waters also have been documented (Madramootoo et al. 1992; Sauer et al. 2000;Stout et al. 2000). Studies have indicated that N and P losses from continuously grazed pastures are generally higher than rotational grazing and ungrazed pastures (Ritter 1988;Mathews et al. 1994).Although livestock grazing activities generally have been reported to adversely impact the hydrology of pasture areas, Sharpley and Syers (1976) determined that P transport due to grazing animals was significantly less than P losses from fertilizer addition. Nash et al. (2000) found that cattle grazing did not result in large stores of available P compared to P fertilization. Mathews et al. (1994) Vegetative filter strip buffers are bands of vegetation located downslope of cropland, livestock grazing areas, and other potential sources of surface runoff and contaminants (Dillaha et al. 1989). Vegetative buffers provide erosion control and filter nutrients, pesticides, sediment, and other pollutants from agricultural runoff by reducing sediment carrier energy. Contaminant re...

This study quantified the effects of a livestock manure-based windrow composting practice with a fly ash composting pad surface and vegetative filter strip (VFS) buffers on losses of runoff, runoff percent of rainfall, total solids, nitrate-nitrogen, ortho-phosphorus (PO 4 -P), and total-phosphorus during natural rainfall events. Runoff data from six events were collected during June and July (early season) and August and September (late season) 60-day duration composting periods from 2002 through 2004 at an Iowa State University research farm near Ames, central Iowa, USA. The research site was selected on uneven terrain with average slopes of 5% and 2% on the VFS buffer and composting pad plot areas, respectively. Runoff treatments were comprised of three compost windrows:VFS buffer area ratios that included 1:1, 1:0.5, and 1:0 (no buffer) control. The 1:1 and 1:0.5 area ratios represented a 6.0-m (20-ft) wide × 23-m (75-ft) long fly ash composting pad area compared to VFS buffer areas of equal and one-half size, respectively. All treatments had three replications for a total of nine runoff plots in a randomized complete block design. Results from the study indicate significantly higher levels (p < 0.05) of runoff, runoff percent of rainfall, total solids, nitrate-nitrogen, PO 4 -P, and total-phosphorus from the 1:0 control plots compared to the 1:1 and 1:0.5 VFS buffer plots. Results also show the 1:1 and 1:0.5 VFS buffer treatments were not significantly different (p < 0.05) and that average runoff loss reductions from the 1:1 and 1:0.5 VFS buffer plots were 98% and 93%, respectively, compared to the 1:0 control plots. These results reflect the effectiveness of VFS buffers for reducing runoff and contaminant losses from a windrow composting site. Compost nutrient mass balance analysis results indicate 41% and 26% of PO 4 -P were lost from the compost windrows during the 2004 early season and late season composting periods, respectively. However, only 0.1% to 0.4% of PO 4 -P was lost to runoff from the 1:0 control plots during the respective 2004 early season and late season composting periods. We hypothesize the relatively lower PO 4 -P losses in runoff may be attributed to potential chemical and physical effects of the fly ash composting pad material. RightsWorks produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted. Abstract: This study quantified the effects of a livestock manure-based windrow composting practice with a fly ash composting pad surface and vegetative filter strip (VFS) buffers on losses of runoff, runoff percent of rainfall, total solids, nitrate-nitrogen, ortho-phosphorus (PO 4 -P), and total-phosphorus during natural rainfall events. Runoff data from six events were collected during June and July (early season) and August and September (late season) 60-day duration composting periods from 2002 through 2004 at an Iowa State University research farm near Ames, central Iowa, US...

Windrow-composted livestock manure has been shown to be less hazardous to the environment compared to manure directly applied to cropland and other agricultural areas. Although offsite contaminant losses through runoff and leaching can occur during the composting process, these losses are suspected to increase under different compost moisture conditions and as composted materials mature. This research quantified the effects of windrow-composted livestock manure and straw bedding components on runoff and infiltration characteristics from laboratory rainfall simulations. Compost samples collected on three dates at approximately the beginning (day 0), middle (day 30), and end (day 60) of a June-July 2004 field research windrow composting period were used for this rainfall simulation study. Replicated compost windrow-shaped cross-section samples were constructed in a specially-designed Plexiglas container apparatus for viewing and recording infiltrated leachate wetting front position boundary movement from simulated rainfall events. Runoff and leachate samples were collected and analyzed for drainage volumes and concentrations and total mass losses of sediment, nitrate-nitrogen (NO 3 -N), and ortho-phosphorus (PO 4 -P) during and following rainfall simulation trials. Leachate wetting front position boundary movement was significantly lower for day 60 compost samples compared among day 0 and day 30 compost sample material. Drainage volume analysis results indicated significantly higher average runoff versus leachate volumes within all compost sampling dates, and runoff volumes were significantly higher among day 30 and day 60 compost samples compared to runoff volumes from day 0 compost samples. Average sediment, NO 3 -N, and PO 4 -P concentrations were significantly higher in leachate versus runoff within all compost sampling dates. Conversely, the total mass losses of these contaminants were significantly higher in runoff compared to leachate within all compost sampling dates. Results of this study suggest that biological and mechanical functions of the composting process reduced compost sample aggregates and increased compost bulk density. We hypothesize that these changes in compost material structure and porosity volume decreased infiltration and increased runoff sediment, NO 3 -N, and PO 4 -P losses during the second and final compost sampling stages of a field windrow composting period. DisciplinesAgricultural Science | Agriculture | Agronomy and Crop Sciences | Bioresource and Agricultural Engineering Comments

The Midwest is well known for agriculture, and Iowa is a leader in corn (Zea mays L.) and soybean (Glycine max [L.] Merr.) production. Fertilizers and chemical pesticides used to increase crop production can adversely affect the soil and water health. Midwest farmers also produce livestock and graze cattle on pastureland that can lead to excessive surface runoff and soil erosion. Establishing vegetative filter strips (VFSs) along the edge of farmland is one of the best management practices (BMPs) to reduce nutrient and sediment loss. However, studies have revealed that the classic VFS design along the length of an agricultural field does not adequately address nonuniform flow through the buffer. New designs are being researched to increase the efficiency of the VFS. In order to accurately implement new design strategies, the runoff flowpaths into the VFS need to be accurately modeled. This research assesses the performance of existing established VFS buffers of selected sites by modeling and analyzing the flow accumulation from the field into the VFS using geographic information system (GIS) and light detection and ranging (LiDAR) derived digital elevation model (DEM) 5 × 5 m data. This study also employed the new coefficient of flow interception (CFI) approach that improves the process of identifying areas where flow is concentrated and designing more efficient filter strips to account for concentrated runoff. In this study, the performance of VFS in three sites was evaluated by developing and using the CFI. Among the three sites, site 1 had very poor efficiency and no flow passes through the VFS, site 2 had low efficiency, and site 3 had excellent efficiency.

Management practices for applying liquid swine manure to minimize surface runoff water pollution and improve crop production can be evaluated by conducting long-term field studies. This article documents results from a sixyear (1996-2001) central Iowa field study that evaluated the effects of swine manure application management practices on soil nutrients, organic matter, pH, crop yield, and discusses potential water quality implications. Swine manure management practices included single-rate (SR) and double-rate (DR) nitrogen (N) based application rates (168 and 336 kg N ha-1 , respectively), three timings (fall injection [FI], winter broadcast [WB], and spring injection [SI]), and two methods (broadcast and injection) of liquid swine manure. Analysis of these practices involved comparing levels of residual soil total phosphorus (P) as Bray-1 available P (RSP), residual soil nitrate-nitrogen (RSN), percent organic matter (OM%), pH, carbon:nitrogen (C:N) ratio, and crop yields (kg ha-1) in a corn-soybean rotation cropping practice. Manure application rates were based on standard crop-available N levels as applied to corn plots and were adjusted for environmental losses. Soil samples were collected immediately prior to commencing the study and after harvest each year and analyzed for RSP, RSN, OM%, pH, and C:N ratio at selected depths in the top 0.30 m of the soil profile. Deep soil core (0-1.22 m) samples also were collected after harvest in 1996 and 2000 and analyzed for RSN as a function of depth in the soil profile. When averaged over the six project years and manure application times for corn plots, these findings showed that DR application plots had significantly higher accumulation of RSP and RSN (32.6% and 36.5%, respectively) versus SR application plots in the top 0.30 m of the soil profile. The RSP for the SI (38.2%) and WB (32.8%) treatments was significantly higher than for the FI treatment on corn plots. The RSN accumulation also was found to be significantly higher for the SI (33.4%) and WB (17.4%) treatments than for the FI treatment on corn plots. The 0-1.22 m deep soil core analysis indicated a higher RSN accumulation in up to 88% of the 1.22 m soil profile depth range for the DR and SI treatments. When averaged across the six years and application rates, corn yield was significantly higher for SI plots (9,596 kg ha-1) versus FI plots (9,236 kg ha-1). The reduction in FI plot corn yield results may have been due largely to excessive leaching of nutrients through the soil profile from post-harvest rainfall during the fall-spring duration. Swine manure SI plots with the higher DR application rate produced the highest average corn yield (10,093 kg ha-1). When averaged over project years and application times, the SI treatment showed an increase of 4.0% in corn yield over the FI treatment. While there were short-term significant increases in OM% for the SI1 treatment during 1996 and 1997, there were no significant cumulative differences in OM% as well as pH and C:N ratio in the soil profile after six ...