J. Thomas Sims’s research while affiliated with University of Delaware and other places

Phosphorus (P) Index evaluations are critical to advancing nutrient management planning in the United States. However, most assessments until now have focused on the risks of P losses in surface runoff. In artificially drained agroecosystems of the Atlantic Coastal Plain, subsurface flow is the predominant mode of P transport, but its representation in most P Indices is often inadequate. We explored methods to evaluate the subsurface P risk routines of five P Indices from Delaware, Maryland (two), Virginia, and North Carolina using available water quality and soils datasets. Relationships between subsurface P risk scores and published dissolved P loads in leachate (Delaware, Maryland, and North Carolina) and ditch drainage (Maryland) were directionally correct and often statistically significant, yet the brevity of the observation periods (weeks to several years) and the limited number of sampling locations precluded a more robust assessment of each P Index. Given the paucity of measured P loss data, we then showed that soil water extractable P concentrations at depths corresponding with the seasonal high water table (WEP WT ) could serve as a realistic proxy for subsurface P losses in ditch drainage. The associations between WEP WT and subsurface P risk ratings reasonably mirrored those obtained with sparser water quality data. As such, WEP WT is seen as a valuable metric that offers interim insight into the directionality of subsurface P risk scores when water quality data are inaccessible. In the long term, improved monitoring and modeling of subsurface P losses clearly should enhance the rigor of future P Index appraisals. Core Ideas We evaluated subsurface P routines of five P Indices in artificially drained soils. Subsurface P ratings mostly accorded with P loads in leachate and ditch drainage. Water extractable P at the seasonal high water table was a proxy for ditch P loss. Useful P Index predictions hinged on accurate depictions of subsurface water flux. Increased monitoring and modeling of subsurface P loss is needed to test P Indices.

Application of phosphorus (P) fertilizers and animal manures to P-rich soils due to the historic use of P inputs can lead to greater P losses. In these soils, we need to manage legacy and new inputs of P in a way that they do not lead to P loss. Studies were conducted to (i) determine the effect of soil type on P leaching and (ii) investigate if changes in dairy and poultry diets can lead to lower P in manures and loss when manures are land applied. Earn 2 CEUs in Soil & Water Management by reading this article and taking the quiz at www.certifiedcropadviser.org/ certifications/self-study/799.

Application of phosphorus (P) fertilizers and animal manures to P‐rich soils due to the historic use of P inputs can lead to greater P losses. In these soils, we need to manage legacy and new inputs of P in a way that they do not lead to P loss. Studies were conducted to (i) determine the effect of soil type on P leaching and (ii) investigate if changes in dairy and poultry diets can lead to lower P in manures and loss when manures are land applied. Earn 2 CEUs in Soil & Water Management by reading this article and taking the quiz at www.certifiedcropadviser.org/certifications/self‐study/799 .

New dietary modifications for dairy (reducing P content in feed) and poultry (addition of feed additives such as phytase) aim to reduce P excretion in manures. Our objective was to investigate if dietary changes were effective at reducing P leaching loss on land application of manures. We used 54 undisturbed lysimeters (30 cm diameter, 50 cm deep) collected from three typical mid‐Atlantic soils. Lysimeters received 85 kg total P ha ⁻¹ from fertilizer (superphosphate), dairy manures generated from low‐ or high‐P diets, or broiler litters generated from normal diet or reduced P‐ and phytase‐amended diets. Lysimeters were irrigated with 50 mm of water each week for 9 wk. The major forms of P in the leachate were dissolved (dissolved unreactive P > dissolved reactive P [DRP]) rather than particulate (total particulate P). The higher P solubility (100%) in superphosphate resulted in greater leaching of DRP, whereas the lower P solubility (<30%) in dairy manures or broiler litters resulted in lower DRP leaching from soils. Preferential flow in two soils caused greater DRP leaching; this effect was more pronounced in the superphosphate‐amended than in the manure/litter‐amended lysimeters. The dairy and poultry dietary modification was effective at reducing the amount of P in manures and litters. However, the application of treatments at similar P rate (85 kg ha ⁻¹ ) resulted in the addition of a higher amount of manure (54–66%) in lysimeters that received low‐P dairy manure–amended and phytase‐amended broiler litter, which then controlled P leaching from soils. Core Ideas Dissolved unreactive P was the major form leached from the mid‐Atlantic soils. Existence of preferential flow pathways in soils caused greater P leaching. Soil and manure characteristics controlled P leaching from soils.

Core Ideas Higher P leaching from P‐saturated mid‐Atlantic soils. Preferential flow caused more P leaching in fine‐textured soils. Matrix flow reduced P leaching from coarse‐textured soils. Use both P saturation ratio and flow pathways to predict the risk of P leaching. Application of phosphorus (P) inputs to soils saturated with legacy P can significantly increase the risk of P leaching and deteriorate water quality. Our objectives were to quantify the effect of soil type and extent of P saturation on P leaching and determine the suitability of a rapid, inexpensive soil P saturation test for use in P leaching risk assessment protocols. We collected 18 undisturbed lysimeters (30‐cm diameter, 50 cm deep), using a tractor‐mounted corer, from three typical mid‐Atlantic soils in Delaware, where P leaching is a concern. The soils were selected on the basis of Mehlich‐3 P saturation ratio (M3‐PSR) of optimum (<0.10) to environmental (>0.15) thresholds. Lysimeters were irrigated with the equivalent of 50 mm of water each week for a total of 16 wk. Concentrations of dissolved reactive P (DRP) and total P in leachate were not significantly different between optimum and environmental M3‐PSR lysimeters before fertilizer application (Weeks 1–8). However, concentrations of DRP and total P significantly increased after fertilizer application at 85 kg P ha ⁻¹ (Weeks 9–16) in the environmental M3‐PSR lysimeters. Among three soils in both M3‐PSR categories, concentrations and loads of P leached were higher from the Matapeake silt loam and Pocomoke sandy loam due to preferential leaching that limited contact of flowing water and P with the soil P‐fixing constituents (Fe, Al, and Ca), while P leaching was lower from Woodstown sandy loam due to matrix flow that resulted in greater interaction of water and P with the soil constituents. These results provide clear evidence of a greater risk of P leaching from P‐saturated soils with preferential flow pathways and show that the M3‐PSR along with information about preferential flow pathways should be used to predict the risk of P leaching.

Animal manures are a valuable source of nutrients for crops and grasslands. However, global intensification of animal production concentrates manure within smaller areas, creating nutrient hot spots. In contrast, nutrient deficits often develop in areas with limited animal production that could benefit from manure applications. A comprehensive approach to manure application is necessary to maximize agricultural value and minimize environmental and human health effects. Regulations and incentive programs that promote beneficial reuse can enhance productive use of manures and prevent environmental problems. Manure transportation programs and infrastructure are needed to relocate manures from areas of nutrient surplus to deficit areas.

The Atlantic Coastal Plain region has had a long history of experimental and applied efforts to exclude phosphorus (P) from drainage waters. Early research focusing upon the chemical controls of soil and sediment P has given way to field studies aimed at refining our understanding of hydrologic pathways and sources of P in drainage effluent. To some extent monitoring has helped to prioritize remedial strategies, with farmstead sources serving as principal sources of concern followed by soils of highest P status. Even then, soils of the Atlantic Coastal Plain are far from homogeneous. While drainage systems are generally designed to address regional water tables, textural discontinuities in coastal plain soils often serve to perch water, routing interflow along surface soil horizons and areas of highest P sorption saturation. Targeting surface soil P alone, however, can neglect substantial reserves in the subsoil. Recent trends in converting drainage ditches to subsurface tile drains present new concerns with regard to P leaching, especially following manure application. Integration of nutrient management, drainage management and agronomic management is necessary to overcome the many pathways that can exacerbate P transfers in this region.

Rapid infiltration basin systems (RIBS) are receiving increased interest for domestic wastewater disposal in rural areas. They rely on natural treatment processes to filter pollutants and use extremely high effluent loading rates, much greater than natural precipitation, applied to a small geographic area instead of disposal to surface water. Concerns exist today that adopting RIBS in areas with shallow groundwater and sandy soils may increase ground and surface water pollution. We conducted a field study of RIBS effects on N and P concentrations in soils and groundwater at Cape Henlopen State Park, Delaware, where a RIBS designed and operated following USEPA guidance has been used for >25 yr. Site and wastewater characteristics (water table of 8 m, Fe- and Al-oxide coatings on soils, organic-rich effluent) were favorable for denitrification and P sorption; however, we found high P saturation, reduced soil P sorption capacity, and significant total P accumulation at depths >1.5 m, factors that could lead to dissolved P leaching. Very low soil inorganic N levels suggest that wastewater N was converted rapidly to NO-N and leached from the RIBS. Extensive groundwater monitoring supported these concerns and showed rapid offsite transport of N and P at concentrations similar to the effluent. Results suggest that high hydraulic loads and preferential flow led to flow velocities that were too large, and contact times between effluent and soils that were too short, for effective N and P attenuation processes. These findings indicate the need for better site characterization and facility designs to reduce and monitor contaminant loss from RIBS in similar settings.

Dissolved organic carbon (DOC) provides a reactive substrate that can facilitate the transport of organic and inorganic contaminants in runoff. The aromatic fractions of DOC are especially important since contaminants are preferentially sorbed onto these fractions. Agricultural practices such as land application of manure can provide substantial inputs of both DOC as well as associated contaminants to agroecosystems. We explored the exports of DOC, estrogens and trace elements in surface runoff from agricultural plots receiving poultry litter. The study was conducted on agricultural soils of the coastal plain in Delaware. Estrogens included free forms: estrone, 17β–estradiol, and estriol; and their glucuronide and sulfate conjugates. Trace elements studied were arsenic, copper, and zinc. Litter treatments included raw litter, pelletized litter and control (no-litter). Treatment plots were 5m wide and 12m long with reduced and no–tillage management practices. The aromatic content of DOC was characterized using specific ultra violet absorbance (SUVA). Surface runoff samples were collected for seven natural storm events over the summer (April-July, 2008). Flow-weighted concentrations of DOC and SUVA from plots receiving litter were significantly (p≤0.10) greater than the control plots. Plots in reduced tillage with raw litter yielded higher DOC concentrations and SUVA values (more aromatic) compared to plots with the pelletized litter. No significant differences (p≤0.10) in DOC and SUVA were observed for litter treatments in no-tillage. Mass exports of estrogens and the trace elements were positively and significantly (p≤0.10) correlated with DOC and SUVA, indicating that DOC, especially its aromatic fractions, played significant role in the exports of these contaminants.

Murine norovirus 1 (MNV-1), Aichi virus (AiV), and human adenovirus 41 (Ad41) were seeded in dairy manure and composted for 60 days, and both the stability of virus genomes and infectious viruses were evaluated. For compost started in late fall, pile temperature reached approximately 54.5 degrees C on day 1 and remained between 55 and 60 degrees C for 3 days. For viral genomes, AiV had an approximate 1.4-log loss of viral genome after 1 day and more than a 3.1-log loss after 2 days; while for MNV-1, there was a roughly 0.6-log reduction on day 1 and a more than 4-log reduction after 5 days. For compost started in late spring, the center temperature reached about 70 degrees C on day 1 and remained warmer than 65 degrees C for 3 days. The MNV-1 viral genome level was below the detection limit (ca. 3.4 log reverse transcriptase and quantitative PCR unit per g) after 1 day. Compared with RNA viruses, the Ad41 DNA genome was more stable in compost started in late spring; there was no reduction in DNA after 1 day, and ca. a 2.1-log loss at 5 and 7 days. For viral infectivity, the AiV infectious concentration was below the detection limit (about 2.8 log tissue culture infectious dose assay per g) after day 1 for both trials 1 and 2, and for Ad41, there was a greater than 4-log reduction of infectivity after 1 day for trial 2. Overall, temperature is a critical factor, which affects the survival of viruses in compost, and the fate of the viral genome in the generated heat is virus dependent as well. For U.S. Environmental Protection Agency Class A compost, current compost regulations require maintaining temperatures between 55 and 70 degrees C for at least for 3 days for a static aerated-pile system. This study indicated that these temperature conditions could effectively inactivate MNV-1, AiV, and Ad41.