Deep soil nitrogen storage slows nitrate leaching through the vadose zone.

Nitrogen (N) fertilizer applications are important for agricultural yield, yet not all the applied N is taken up by crops, leading to surplus N storage in soil or leaching to groundwater and surface water. Leaching loss of fertilizer N represents a cost for farmers and has consequences for human health and the environment, especially in the southern Willamette Valley, Oregon, USA, where groundwater nitrate contamination is prevalent. While improved nutrient management and conservation practices have been implemented to minimize leaching, nitrate levels in groundwater continue to increase in many long-term monitoring wells. To elucidate controls on leaching rates and N dynamics in agricultural soils across soil depths, and in response to seasonal and annual variation in management (e.g., fertilizer input amount and summer irrigation), we intensively monitored the transport of water and nitrate every two weeks for four years through the vadose zone at three depths (0.8, 1.5, and 3.0 m) in a sweet corn (maize) field. Though nitrate leaching was highly variable among lysimeters at the same depth and across years, a strong pattern emerged: annual nitrate leaching significantly decreased with depth across the study, averaging ~104 kg N ha-1 yr-1 near the surface (0.8 m) versus ~56 kg N ha-1 yr-1 in the deep soil (3.0 m), a 54% reduction in leaching between the soil layers. Even though crops were irrigated in summer, most leaching (~72% below 3.0 m) occurred during the wet fall and winter. Based on steady state assumptions, a net equivalent of ~29% of surface N inputs leached below 3.0 m into the deeper soil and groundwater, while ~44% was removed in crop harvest, indicating considerable N retention in the soil (~27% of inputs or approximately 58 kg N ha-1 yr-1). The accumulation and long-term dynamics of deep soil N is a legacy of agricultural management that should be further studied to better manage and reduce nitrate loss to groundwater.

Reuse of concentrated animal feeding operation wastewater on agricultural lands.

Concentrated animal feeding operations (CAFOs) generate large volumes of manure and manure-contaminated wash and runoff water. When applied to land at agronomic rates, CAFO wastewater has the potential to be a valuable fertilizer and soil amendment that can improve the physical condition of the soil for plant growth and reduce the demand for high quality water resources. However, excess amounts of nutrients, heavy metals, salts, pathogenic microorganisms, and pharmaceutically active compounds (antibiotics and hormones) in CAFO wastewater can adversely impact soil and water quality. The USEPA currently requires that application of CAFO wastes to agricultural lands follow an approved nutrient management plan (NMP). A NMP is a design document that sets rates for waste application to meet the water and nutrient requirements of the selected crops and soil types, and is typically written so as to be protective of surface water resources. The tacit assumption is that a well-designed and executed NMP ensures that all lagoon water contaminants are taken up or degraded in the root zone, so that ground water is inherently protected. The validity of this assumption for all lagoon water contaminants has not yet been thoroughly studied. This review paper discusses our current level of understanding on the environmental impact and sustainability of CAFO wastewater reuse. Specifically, we address the source, composition, application practices, environmental issues, transport pathways, and potential treatments that are associated with the reuse of CAFO wastewater on agricultural lands.

Analysis of lagoon samples from different concentrated animal feeding operations for estrogens and estrogen conjugates.

Although Concentrated Animal Feeding Operations (CAFOs) have been identified as potentially important sources for the release of estrogens into the environment, information is lacking on the concentrations of estrogens in whole lagoon effluents (including suspended solids) which are used for land application. Lagoons associated with swine, poultry, and cattle operations were sampled at three locations each for direct analysis for estrogens by GC/ MS/MS and estrogen conjugates by LC/MS/MS. Estrogen conjugates were also analyzed indirectly by first subjecting the same samples to enzyme hydrolysis. Solids from centrifuged samples were extracted for free estrogens to estimate total estrogen load. Total free estrogen levels (estrone, 17alpha-estradiol, 17beta-estradiol, estriol) were generally higher in swine primary (1000-21000 ng/L), followed by poultry primary (1800-4000 ng/L), dairy secondary (370-550 ng/L), and beef secondary (22-24 ng/L) whole lagoon samples. Swine and poultry lagoons contained levels of 17(alpha-estradiol comparable to those of 17beta-estradiol. Confirmed estrogen conjugates included estrone-3-sulfate (2-91 ng/L), 17beta-estradiol-3-sulfate (8-44 ng/L), 17alpha-estradiol-3-sulfate (141-182 ng/L), and 17beta-estradiol-17-sulfate (72-84 ng/L) in some lagoons. Enzymatic hydrolysis indicated the presence of additional unidentified estrogen conjugates not detected bythe LC/MS/MS method. In most cases estrogen conjugates accounted for at least a third of the total estrogen equivalents. Collectively, these methods can be used to better determine estrogen loads from CAFO operations, and this research shows that estrogen conjugates contribute significantly to the overall estrogen load, even in different types of CAFO lagoons.

Quantitation of estrogens in ground water and swine lagoon samples using solid-phase extraction, pentafluorobenzyl/trimethylsilyl derivatizations and gas chromatography-negative ion chemical ionization tandem mass spectrometry.

A method was developed for the confirmed identification and quantitation of 17beta-estradiol, estrone, 17alpha-ethynylestradiol and 16alpha-hydroxy-17beta-estradiol (estriol) in ground water and swine lagoon samples. Centrifuged and filtered samples were extracted using solid-phase extraction (SPE), and extracts were derivatized using pentafluorobenzy] bromide (PFBBR) and N-trimethylsilylimidazole (TMSI). Analysis was done using negative ion chemical ionization (NICI) gas chromatography-mass spectrometry-mass spectrometry (GC-MS-MS). Deuterated analogs of each of the estrogens were used as isotope dilution standards (IDS) and were added to the samples before extraction. A limit of quantitation of 1 ng/l in ground water was obtained using 500 ml of ground water sample, 1.0 ml of extract volume and the lowest calibration standard of 0.5 pg/microl. For a 25 ml swine lagoon sample, the limit of quantitation was 40 ng/l. The average recovery of the four estrogens spiked into 500 ml of distilled water and ground water samples (n = 16) at 2 ng/l was 103% (S.D. 14%). For 25 ml of swine lagoon samples spiked at 500, 1000 and 10,000 ng/l, the average recovery for the four estrogens was 103% (S.D. 15%). The method detection limits (MDLs) of the four estrogens spiked at 2 ng/l in a 500 ml of ground water sample ranged from 0.2 to 0.6 ng/l. In swine lagoon samples from three different types of swine operations, estrone was found at levels up to 25,000 ng/l, followed by estriol and estradiol up to levels at 10,000 and 3000 ng/l, respectively. It was found that pretreatment of swine lagoon samples with formaldehyde was necessary to prevent conversion of estradiol to estrone.