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Concentrated animal feeding operations emit trace gases such as ammonia (NH 3 ), methane (CH 4 ), carbon dioxide (CO 2 ), and nitrous oxide (N 2 O). The implementation of air quality regulations in livestock-producing states increases the need for accurate on-farm determination of emission rates. The objective of this study was to determine the emission rates of , respectively. The open lot areas generated the greatest emissions of NH 3 , CO 2 , and N 2 O, contributing 78, 80, and 57%, respectively, to total farm emissions. Methane emissions were greatest from the lots in the spring (74% of total), after which the wastewater pond became the largest source of emissions (55% of total) for the remainder of the year. Data from this study can be used to develop trace gas emissions factors from open-lot dairies in southern Idaho and potentially other open-lot production systems in similar climatic regions.

The number of dairy cows in Idaho has increased by approximately 80% in the last decade, with the majority of these facilities located in southern Idaho, causing air quality concerns in this region. To determine the potential air quality impacts of these facilities, we measured ammonia (NH 3), methane (CH 4), and nitrous oxide (N 2 O) concentrations over the pens, wastewater storage pond, and composting area on a 700-cow open-lot dairy using open-path Fourier transform infrared spectrometry (OP/FTIR). Concentrations were measured for one or two days at each location during January, March, June, and September. Median NH 3 concentrations over the pens, storage pond, and composting area ranged from 0.14 to 0.39 ppmv, 0.04 to 0.17 ppmv, and 0.06 to 0.22 ppmv, respectively, with concentrations tending to be lower in January. Average CH 4 concentrations over the pens, storage pond, and composting area ranged from 2.07 to 2.80 ppmv, 1.87 to 2.15 ppmv, and 1.71 to 1.76 ppmv, respectively. Average N 2 O concentrations ranged from 0.31 to 0.33 ppmv for all areas, which was similar to global background N 2 O concentrations. Combined ammonia emissions for the pen and storage pond areas, calculated with a backward Lagrangian stochastic inverse-dispersion technique, were 0.

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Phosphorus (P) often limits the eutrophication of streams, rivers, and lakes receiving surface runoff. We evaluated the relationships among selected soil P availability indices and runoff P fractions where manure, whey, or commercial fertilizer applications had previously established a range of soil P availabilities on a Portneuf silt loam (coarse-silty, mixed, superactive, mesic Durinodic Xeric Haplocalcid) surface-irrigated with Snake River water. Water-soluble P, Olsen P (inorganic and organic P), and iron-oxide impregnated paperextractable P (FeO-P,) were determined on a 0.03-m soil sample taken from the bottom of each furrow before each irrigation in fall 1998 and spring 1999. Dissolved reactive phosphorus (DRP) in a 0.45-µm filtered runoff sample, and iron-oxide impregnated paperextractable P (FeO-P" ), total P, and sediment in an unfiltered runoff sample were determined at selected intervals during a 4-h irrigation on 18.3-m field plots. The 1998 and 1999 data sets were combined because there were no significant differences. How-weighted average runoff DRP and Fe0-P,, concentrations increased linearly as all three soil P test concentrations increased. The average runoff total P concentration was not related to any soil P test but was linearly related to sediment concentration. Stepwise regression selected the independent variables of sediment, soil lime concentration, and soil organic P extracted by the Olsen method as related to average runoff total P concentration. The average runoff total P concentration was 1.08 mg ' at a soil Olsen P concentration of 10 mg kg'. Soil erosion control will be necessary to reduce P losses in surface irrigation runoff.

Demonstrating positive environmental benefits of alternative N fertilizer management strategies, without adversely affecting crop growth or yield, was a major goal for the Midwest Management Systems Evaluation Areas (MSEA) program. Our project objectives within this program were to quantify the effects of split-and single-N fertilization strategies on NO3-N concentration and loss in subsurface drain effluent and N accumulation and yield of corn (Zea mays L.) and soybean [Glycine max (L.) Merr.]. The study was conducted on glacial till derived soils in northeast Iowa from 1993 through 1995 using no-till and chisel plow tillage treatments. One-third of the 2,611 effluent samples had NO3-N concentrations greater than 10 mg L-1. Split applying fertilizer N based on pre-sidedress soil nitrate test (PSNT) results significantly increased corn yield for both tillage treatments in the extremely wet 1993 without increasing NO3-N loss in drain effluent. Increased grain yield also resulted in significantly more N removal. When fertilizer N was applied based on the PSNT, no-till and chisel treatments had similar NO3-N losses and concentrations. Average flowweighted NO3-N concentrations in drain effluent were not increased when larger amounts of fertilizer were applied based on PSNT. However, prior crop and tillage practices and differences in drain flow volume caused significant differences in NO3-N losses and concentrations. These results suggest that spatial differences in flow volume are a major factor determining NO3-N loss in drainage effluent. Significant differences suggest that combining no-tillage practices with split N fertilizer management strategies can have positive environmental benefits without reducing corn yield.

Many semiarid and arid soils are prone to irrigation-induced erosion. Polyacrylamide (PAM) greatly reduces erosion from furrow irrigation. We hypothesized that PAM applied via sprinklers will provide erosion control and benefit water infiltration and aggregate stability. Screened (6.4 mm) Rad silt loam (coarse silty, mixed, superactive mesic Durinodic Xeric Haplocambid) was placed in 1.5 by 1.2 by 0.2 m steel boxes with 2.4% slope. An oscillating nozzle, 3 m above the soil, produced a median drop size of 1.2 mm diameter. We applied 0, 1, 2, 4, and 6 kg ha' PAM in 20 mm of water in the first irrigation, followed by two 20-mm water-only irrigations. In a second test, we applied 0, 2, and 4 kg ha ' PAM in 8 mm of water in the first irrigation, followed by two 20-mm water-only irrigations. Two kilograms per hectare PAM in the first 20-mm irrigation reduced runoff 70% and soil loss 75% compared to control. Polyacrylamide in 8 mm of water was less effective. Polyacrylamide in the 20-mm irrigation did not affect tension infiltration; PAM in the 8-mm irrigation doubled tension infiltration following the third irrigation. Wet aggregate stability following the first irrigation was greater in all PAM treatments than on the check. With 2 kg ha" PAM in the 20-mm irrigation, it was 55%; in 8 mm, 77%. Polyacrylamide applied in the first irrigation at low rates effectively reduced runoff and erosion. Erosion was more effectively controlled than runoff.