Land application of manure, while beneficial to soil health and plant growth, can lead to an overabundance of nutrients and introduction of emerging contaminants into agricultural fields. Compared with surface application of manure, subsurface injection has been shown to reduce nutrients and antibiotics in surface runoff. However, less is known about the influence of subsurface injection on the transport and persistence of antibiotic-resistant microorganisms. We simulated rainfall to field plots at two sites (one in Virginia and one in Pennsylvania) 1 or 7 d after liquid dairy manure surface and subsurface application (56 Mg ha-1 ) and monitored the abundance of culturable antibiotic-resistant fecal coliform bacteria (ARFCB) in surface runoff and soils for 45 d. We performed these tests at both sites in spring 2018 and repeated the test at the Virginia site in fall 2019. Manure subsurface injection, compared with surface application, resulted in less ARFCB in surface runoff, and this reduction was greater at Day 1 after application compared with Day 7. The reductions of ARFCB in surface runoff because of manure subsurface injection were 2.5-593 times at the Virginia site in spring 2018 and fall 2019 and 4-5 times at the Pennsylvania site in spring 2018. The ARFCB were only detectable in the 0-to-5-cm soil depth within 14 d of manure surface application but remained detectable in the injection slits of manure subsurface-injected plots even at Day 45. This study demonstrated that subsurface injection can significantly reduce surface runoff of ARFCB from manure-applied fields.

Management-induced changes in soil carbon (C) and nitrogen contents were difficult to document in these soils because much of the observed difference in soil organic matter (SOM) levels was due to the heterogeneity of texture and drainage characteristics. The kinds and amounts of soil amendments applied and plant residues returned impact SOM and related characteristics by their effect on microorganisms, on the supply of plant-available nutrients, and on soil structure. The amount of C translocated to the roots of each plant species in a crop rotation and the structure of these root systems could be the most important factor affecting SOM dynamics. An integral component of a sustainable agroecosystem is the presence of a continual supply of SOM to provide substrate for an active, healthy soil biological community, an environment for vigorous plant-root development which resists soil erosion, and adequate nutrients for plant growth.

Eutrophication and sedimentation are pervasive challenges in many agricultural watersheds. Recent research has promoted shallow-disk manure injection as a means of mitigating phosphorus (P) losses in runoff while maintaining the water quality benefits of no-till, such as reduced particulate P and sediment losses. However, the precision and accuracy of field studies seeking to quantify the effectiveness of shallow-disk injection as a P mitigation strategy are substantially constrained by hydrologic variability across spatial and temporal scales. In this study, overland and subsurface flow from twelve plots in central Pennsylvania (PA) were measured and sampled for all P constituents and total solids (TS) from January 2013 to May 2017. We regressed loads of total P (TP), dissolved P (DP), particulate P (PP), and TS against flow depths to evaluate how P and TS losses changed with increasing flow. The results revealed dilution of all P constituents and near-chemostatic behavior (little change in concentration with change in flow) for TS for both application methods. Shallow-disk injection was found to be more effective than broadcasting in promoting dilution of DP, and to a lesser extent, TP. In contrast, the broadcast plots showed stronger dilution patterns than did the injection plots for PP, and there was no difference between application methods for TS. Variability among plots within each manure application practice was largely dependent on relative contributions of overland and subsurface flow due to increased dilution of P by subsurface flow. Overall, shallow-disk injection appears to be an effective practice to reduce DP and TP losses without negating the erosion-reducing benefits of no-till.

Eutrophication and sedimentation are pervasive challenges in the Chesapeake Bay watershed. Shallow-disk manure injection is a promising technology to mitigate phosphorus (P) losses in runoff while maintaining the water quality benefits of no-till, including reducing particulate P and sediment losses. However, its effectiveness as a P mitigation strategy is not fully understood, as hydrologic variability exists across spatial and temporal scales, confounding the results of field studies seeking to quantify the benefits of shallow-disk injection. In this study, we regressed loads of total solids (TS), total P (TP), dissolved P (DP), and particulate P (PP) against flow depths to evaluate the effectiveness of shallow-disk manure injection versus broadcasting for reducing P and sediment losses. Overland and subsurface flow from twelve plots in central Pennsylvania were measured and sampled for TS and P from January 2013 to May 2017. The plots received manure via either surface broadcasting or shallow-disk injection for three years, followed by two years of broadcasting across all plots. Load-discharge (L-Q) relationships were developed to determine how P and TS losses changed with increasing flow. L-Q analyses revealed dilution of all P constituents and near-chemostatic behavior for TS for both application methods. Shallow-disk injection was more effective in promoting dilution of DP, and to a lesser extent, TP. Though, broadcast plots showed stronger dilution patterns than injection plots for PP, and there was no difference between application methods for TS. Intra-practice variability was largely dependent on relative contributions from overland and subsurface flow, due to increased dilution from subsurface flow. Overall, shallow-disk injection appears to be an effective practice to reduce TP and DP losses without negating the erosion-reducing benefits of no-till.

Most empirical studies of field management effects on runoff water quality rely on edge-of-field monitoring, which is generally unreplicated and prone to high variances, or small plots, which constrain the use of conventional farm equipment and can hinder insight into landscape processes that drive hydrology. We sought to develop field-scale lysimeters that were sufficiently large to support assessment of landscape processes but also replicated to allow quantitative comparisons of hydrologic processes. A hillslope underlain by limestone bedrock with a recent history of hydrologic observation was selected in central Pennsylvania. Twelve 15 m x 27 m plots were established and defined by earthen berms on all sides to isolate and collect overland flow, along with tile drains to collect shallow lateral flow. Over three years, considerable variability in site hydrology was observed between lysimeters, highlighting differences in the extent of hydrologic isolation of some lysimeters as well as in flows that potentially bypassed our collection infrastructure. Even so, clear patterns were observed in surface and subsurface flow that enabled grouping of plots based on hydrologic similarities. Results illustrate the experimental opportunities and limitations of developing field-scale lysimeters for agronomic inference.

Developing successful mitigation strategies for emerging contaminants can be difficult due to incomplete understanding of factors controlling their fate and transport. A variety of data analysis techniques can be used to assess the fate and transport behavior of pollutants in runoff water. Here, we use concentration-discharge, load discharge, and coefficient of variation relationships to examine how two methods of dairy manure application (surface broadcast and shallow disk injection) affect the transport dynamics of estrogens, total dissolved phosphorus (TDP), and dissolved organic carbon (DOC). Nine surface runoff events were sampled from Oct 2014 June 2015 from 12 research plots (six with each application method) in Central Pennsylvania after fall application. The plots received inorganic fertilizer for 15 years, but only four manure applications since 2012. Both TDP and DOC exhibited similar transport behavior under both manure application methods that indicate transport-limited control of export, potentially due to legacy sources in soils. However, estrogen loads exhibited dilution responses, a sign of source-limited controls. The strength of the dilution response for estrogens was greater for surface applied manure relative to the injected manure, suggesting that manure application methods can be used to control the mobilization potential of estrogens. Additionally, results suggest the longer-term application history of inorganic fertilizer led to the transport-limited dynamics exhibited by TDP, while the short-term application history of manure caused estrogen transport to be source-limited. Our findings provide insight into how anthropogenic drivers (application type, method, and history) and natural drivers (hydrology, biogeochemistry) are interconnected in agricultural fields, and point to opportunities for protecting, downstream water quality.

Sustainable nutrient management requires redistribution of livestock manure from nutrient‐excess areas to nutrient‐deficit areas. Field experiments were conducted to assess agronomic and environmental effects of different poultry litter application methods (surface vs. subsurface) and timings (fall vs. spring) in a potential manure‐importing region in the Chesapeake Bay Watershed in the United States. Earn 0.5 CEUs in Nutrient Management by reading this article and taking the quiz at www.certifiedcropadviser.org/certifications/self‐study/798 .

Phosphorus (P) has been linked to eutrophication in surface waters because it is a limiting nutrient for algal growth, and recent studies have shown that P transport through subsurface flow is of growing concern. In this study we amended dairy and poultry manures with lanthanum (La) and ytterbium (Yb) chlorides to assess the efficacy of using rare earth element (REE) chloride amendments in reducing P leaching through intact soil columns and to determine the major pathways of applied P leaching. Significant reductions in dissolved P. (DP; 56% to 64%), particulate P (PP; 22% to 36%), and total P (TP; 41% to 51%) in leachate were seen when dairy manure was amended with REE-chlorides, but no significant reductions in these P fractions were seen in amended poultry litter. Differences in P leaching losses between the two REE-amended manures were likely due to better mixing and dissolution of the REE-chlorides and better precipitation of an insoluble particulate REE-phosphate salt in the liquid manures prior to being applied. Very little vertical transport of REEs was observed in soil leachate over repeated events. Elevated concentrations of REEs along soil macropores at depths greater than 15 cm (5.9 in) suggest the importance of this pathway. However, due to the extremely low concentrations of REEs found at depth and the much higher values of soil P, the ability to "label" the manures with REEs to track P through macropores in the soil was only suggestive and by no means conclusive. Results point to the efficacy of REE-chlorides in lowering P solubility in liquid manures but limited potential in tracking subsurface transport pathways of applied manure P in soils.

Leaching of phosphorus (P) mobilizes edaphic and applied sources of P and is a primary pathway of concern in agricultural soils of the Delmarva Peninsula, which defines the eastern boundary of the eutrophic Chesapeake Bay. We evaluated P leaching before and after poultry litter application from intact soil columns (30 cm diameter × 50 cm depth) obtained from low- and high-P members of four dominant Delmarva Peninsula soils. Surface soil textures ranged from fine sand to silt loam, and Mehlich-3 soil P ranged from 64 to 628 mg kg. Irrigation of soil columns before litter application pointed to surface soil P controls on dissolved P in leachate (with soil P sorption saturation providing a stronger relationship than Mehlich-3 P); however, strong relationships between P in the subsoil (45-50 cm) and leachate P concentrations were also observed ( = 0.61-0.73). After poultry litter application (4.5 Mg ha), leachate P concentrations and loads increased significantly for the finest-textured soils, consistent with observations that well-structured soils have the greatest propensity to transmit applied P. Phosphorus derived from poultry litter appeared to contribute 41 and 76% of total P loss in leachate from the two soils with the finest textures. Results point to soil P, including P sorption saturation, as a sound metric of P loss potential in leachate when manure is not an acute source of P but highlight the need to factor in macropore transport potential to predict leaching losses from applied P sources.

Leaching of nutrients through agricultural soils is a priority water quality concern on the Atlantic Coastal Plain. This study evaluated the effect of tillage and urea application on leaching of phosphorus (P) and nitrogen (N) from soils of the Delmarva Peninsula that had previously been under no-till management. Intact soil columns (30 cm wide × 50 cm deep) were irrigated for 6 wk to establish a baseline of leaching response. After 2 wk of drying, a subset of soil columns was subjected to simulated tillage (0-20 cm) in an attempt to curtail leaching of surface nutrients, especially P. Urea (145 kg N ha) was then broadcast on all soils (tilled and untilled), and the columns were irrigated for another 8 wk. Comparison of leachate recoveries representing rapid and slow flows confirmed the potential to manipulate flow fractions with tillage, albeit with mixed results across soils. Leachate trends in the finer-textured soil suggest that tillage impeded macropore flow and forced greater matrix flow. Despite significant vertical stratification of soil P that suggested tillage could prevent leaching of P via macropores from the surface to the subsoil, tillage had no significant impact on P leaching losses. Relatively high levels of soil P below 20 cm may have served as the source of P enrichment in leachate waters. However, tillage did lower losses of applied urea in leachate from two of the three soils, partially confirming the study's premise that tillage would destroy macropore pathways transmitting surface constituents to the subsoil.

Stacking poultry litter in fields prior to land application is a common practice that provides important logistical benefits to farmers, but may lead to environmental losses of nutrients. A 2-year field study was conducted to evaluate phosphorus (P) and nitrogen (N) losses from poultry litter stacks with and without a protective cover. Surface runoff from the litter stacks and leachate through two texturally contrasting soils (sand and silt loam) was monitored using a combination of runoff collectors and zero-tension lysimetry. Nutrient losses in surface runoff were small (total P < 3 g m−2; total inorganic N < 7 g m−2), particularly when compared with losses in leachate (total P < 60 g m−2; total inorganic N < 290 g m−2). Covering stacks reduced leachate total P losses by 25–100 times and total inorganic N losses by 25–770 times, such that leachate nutrient losses from covered stacks were similar to that in the controls with no manure stacking. Despite relatively small nutrient losses from litter stacks over the 2-year study, results point to substantial nutrient accumulation in soil after repeated stacking. Water-extractable P concentrations in upper 5-cm soils were similar between covered (120–240 mg kg−1) and uncovered stacks (140–250 mg kg−1), but soil nitrate-N concentrations were much higher under the covered stack (80–140 mg kg−1) than the uncovered stack (<5 mg kg−1). This study clearly points to benefits of covering litter stacks, but highlights long-term concerns with regard to soil nutrient accumulation.

The application of poultry (Gallus gallus domesticus) litter to agricultural soils may exacerbate losses of trace elements in runoff water, an emerging concern to water quality. We evaluated trace elements (arsenic [As], mercury [Hg], selenium [Se], and zinc [Zn]) in surface runoff and leachate from an agricultural soil with and without poultry litter application. Litter from a commercial operation was applied by three methods—broadcast application, subsurface placement, and broadcast application followed by disking—to no-till soils with a history of receiving litter. Soil monolith lysimeters (61 by 61 by 61 cm)(24 by 24 by 24 in) were extracted from each of the treatments and subjected to rainfall simulation (1 hour, 61 mm h−1 [2.4 in hr−1]) 15 and 42 days after litter application. Broadcasting poultry litter significantly increased concentrations (mg L−1) and loads (g ha−1) of As and Zn in runoff during the first event relative to other application methods. Notably, incorporating litter, either by disking after broadcasting or by subsurface placement, lowered As and Zn in runoff to near background levels by the second event, and there were no significant differences in As and Zn between any of the treatments. While Hg and Se were detected in runoff, they likely derived from edaphic sources as they were not detected in the litter nor did they differ significantly between treatments. Results point to poultry litter as a temporary source of some trace elements to runoff. This source can be readily controlled by adjusting application method.

Manure presents one of the greatest challenges to livestock (dairy and beef cattle, swine, poultry, equine, sheep, llamas, etc.) operations in the Chesapeake Bay Watershed, serving both as resource and liability. The Chesapeake Bay is threatened by excessive nutrient loadings, and, according to the US Environmental Protection Agency (USEPA), manure is the source of 18% of the nitrogen and 27% of the phosphorus entering the Chesapeake Bay annually (figure 1) (Chesapeake Bay Program 2010). Developing economical, practical, and effective manure management options for livestock producers will not only contribute to the restoration of the Chesapeake Bay, but will also provide a model for other areas where water quality and livestock production objectives must be balanced.

The application of poultry litter to soils is a water quality concern on the Delmarva Peninsula, as runoff contributes P to the eutrophic Chesapeake Bay. This study compared a new subsurface applicator for poultry litter with conventional surface application and tillage incorporation of litter on a Coastal Plain soil under no-till management. Monolith lysimeters (61 cm by 61 cm by 61 cm) were collected immediately after litter application and subjected to rainfall simulation (61 mm h(-1) 1 h) 15 and 42 d later. In the first rainfall event, subsurface application of litter significantly lowered total P losses in runoff (1.90 kg ha(-1)) compared with surface application (4.78 kg ha(-1)). Losses of P with subsurface application were not significantly different from disked litter or an unamended control. By the second event, total P losses did not differ significantly between surface and subsurface litter treatments but were at least twofold greater than losses from the disked and control treatments. A rising water table in the second event likely mobilized dissolved forms of P in subsurface-applied litter to the soil surface, enriching runoff water with P. Across both events, subsurface application of litter did not significantly decrease cumulative losses of P relative to surface-applied litter, whereas disking the litter into the soil did. Results confirm the short-term reduction of runoff P losses with subsurface litter application observed elsewhere but highlight the modifying effect of soil hydrology on this technology's ability to minimize P loss in runoff.

Due to widespread adoption of no-till, there is considerable interest in methods of incorporating manure into soil with minimal disturbance. Watershed and nutrient trading programs rely upon empirical water quality findings to promote manure application methods and to extrapolate the water quality benefits of those methods. Rainfall simulation studies have been a key source of input into the water quality benefits of manure management alternatives. Rainfall simulation studies offer a means of controlling key storm variables and selecting the timing of events, often with an eye to representing worst case scenarios. However, the control offered by these studies results in limited representation of management, climatic, and hydrologic variables. To better understand the effect of assessment method on management recommendations, we compared edge-of-field findings from controlled rainfall events with those obtained under natural conditions.

Incorporation of manure slurry under reduced tillage conditions remains a challenge in the northeastern US. New technologies to directly incorporate slurry are available but their agronomic and environmental benefits have generally not been quantified. This study evaluated the effects of five manure slurry application methods on phosphorus (P) loss in runoff (broadcasting with and without incorporation by tillage, shallow disk injection, banded application and aeration, and pressurized injection) and a control (no manure). Research was conducted over a 2 year period in central Pennsylvania on a well-drained Hagerstown silt loam (fine, mixed, semiactive, mesic Typic Hapludalf) under corn (Zea mays L.) production. Approximately 72 h after dairy (Bos Taurus) slurry application (56,000 l ha−1) to 10 × 13 m plots, a single rainfall simulation (68 mm h−1) was conducted in triplicate on 10 × 2 m areas within the plots. Trends in total P losses in runoff (kg ha−1) from plots varied between years and treatments. Aeration yielded lower losses than all other treatments in 2006 and was amongst the lowest in 2007 with losses statistically similar to shallow disk and pressure injection. Remarkably, few differences were apparent in losses of dissolved reactive P between treatments, reflecting high variability in runoff depths. Indeed, variability in runoff depths resulted in some unexpected trends, including high loads from the unamended control and modest loads from the tillage treatment. Results highlight tradeoffs in alternative manure slurry application practices but point to the potential to significantly lower runoff P losses from reduced tillage systems receiving manure slurry.

Poultry production on Delmarva is a primary source of poultry litter used to fertilize farmland to support staple crop production. This trend over long period of time may cause a build-up of trace elements such as As, Hg and Zn in soils, which can contaminate water resources at relatively low levels. Additionally, the widespread adoption of no-till farming on Delmarva and the usual practice of surface application of poultry litter have led to elevated trace elements transport in surface run-off. Three poultry litter amendment treatments – broadcast (conventional no-till), subsurface application and broadcast/disked were compared in this study with an unamended control (no litter). Immediately after litter application, lysimeters (61 x 61 x 61cm) were collected from each of the treatment areas, set at 3% slope and subjected to rainfall simulation (1 hr, 6.06 cm/hr) 15 and 42 days after litter application. Runoff samples were analyzed for dissolved and particulate trace elements (arsenic, selenium, mercury, and zinc). USDA-ARS subsurface (subsurfer) application and broadcasting followed by disking lowered losses of As and Zn in surface runoff by about 2-fold as compared to the broadcast application after the first rainfall simulation. However, the differences disappeared by the second rainfall event. No differences were observed between treatments in losses of Hg and Se in runoff for both rainfall events. These results suggest that incorporation of poultry litter by subsurface application or broadcast followed by disking would help lower trace elements of concern such as As in surface runoff.

Poultry litter provides a rich nutrient source for crops, but the usual practice of surface-applying litter can degrade water quality by allowing nutrients to be transported from fields in surface runoff while much of the ammonia (NH3)-N escapes into the atmosphere. Our goal was to improve on conventional titter application methods to decrease associated nutrient losses to air and water while increasing soil productivity. We developed and tested a knifing technique to directly apply dry poultry litter beneath the surface of pastures. Results showed that subsurface litter application decreased NH3-N volatilization and nutrient losses in runoff more than 90% (compared with surface-applied litter) to levels statistically as low as those from control (no litter) plots. Given this success, two advanced tractor-drawn prototypes were developed to subsurface apply poultry litter in field research. The two prototypes have been tested in pasture and no-till experiments and are both effective in improving nutrient-use efficiency compared with surface-applied litter, increasing crop yields (possibly by retaining more nitrogen in the soil), and decreasing nutrient losses, often to near background (control plot) levels. A paired-watershed study showed that cumulative phosphorus losses in runoff from continuously grazed perennial pastures were decreased by 55% over a 3-yr period if the annual poultry litter applications were subsurface applied rather than surface broadcast. Results highlight opportunities and challenges for commercial adoption of subsurface poultry litter application in pasture and no-till systems.

Management of poultry litter on the Delmarva Peninsula is critical to reducing phosphorus losses to the Chesapeake Bay. New poultry litter incorporation technologies have shown promise at reducing phosphorus losses, but their effectiveness has not been tested in this environmentally sensitive region. This study evaluates subsurface leaching losses of three litter application methods, including surface broadcast, surface broadcast with disking, and subsurface litter incorporation with a novel litter incorporator developed by the USDA Agricultural Research Service. Cube-shaped soil lysimeters (61 × 61 × 61 cm [24 × 24 × 24 in]) were extracted from high phosphorus (P) (Mehlich-3 P is greater than 500 mg kg−1) agricultural soils on the University of Maryland Eastern Shore Research Farm near Princess Anne, Maryland, and were subjected to two rainfall simulation events that were separated by 11 semiweekly soaking-type irrigation events. The average cumulative total phosphorus loss was highest for the subsurface litter incorporation method (0.48 kg ha−1 [0.43 lb ac−1]) and was lowest for the no litter control (0.19 kg ha−1 [0.17 lb ac−1]). Particulate P loss among manure treatments ranged from 58% to 64% of total P loss. Total phosphorus losses were strongly correlated to total phosphorus concentration in the leachate (coefficient of determination [r2] ≥ 0.84), indicating availability of P in applied litter to be the primary control of P in leachate. Soil properties also impacted P leaching losses, with the soils possessing a higher sand content and having a shallower depth to the sandy subsoil, yielding higher cumulative total P losses (0.64 kg ha−1 [0.57 lb ac−1]). Although the subsurface litter incorporator increased total P leaching losses, a concern on the Delmarva Peninsula, opportunity exists to modify the subsurface incorporator design using zone tillage, potentially reducing the leaching losses.