LOADING FUNCTIONS FOR PREDICTING NUTRIENT LOSSES FROM COMPLEX WATERSHEDS1

ABSTRACT: A loading function methodology is presented for predicting runoff, sediment, and nutrient losses from complex watersheds. Separate models are defined for cropland, forest, urban and barnyard sources, and procedures for estimating baseflow nutrients are provided. The loading functions are designed for use as a preliminary screening tool to isolate the major contributors in a watershed. Input data sources are readily available and the functions do not require costly calibrations. Data requirements include watershed land use and soil information, daily precipitation and temperature records and rainfall erosivities. Comparison of predicted and measured water, sediment, and nutrient runoff fluxes for the West Branch Deleware River in New York, indicated that runoff was underpredicted by about 14 percent while dissolved nutrients were within 30 percent of observed values. Sediment and solid-phase nutrients were overpredicted by about 50 percent. An annual nutrient budget for the West Branch Delaware River showed that cornland was the major source of sediment, solid phase nutrients, and total phosphorus. Waste water treatment plants and ground water discharge contributed the most dissolved phosphorus and dissolved nitrogen, respectively.     

Prairie and turf buffer strips for controlling runoff from paved surfaces

Eutrophication of surface waters due to nonpoint source pollution from urban environments has raised awareness of the need to decrease runoff from roads and other impervious surfaces. These concerns have led to precautionary P application restrictions on turf and requirements for vegetative buffer strips. The impacts of two plant communities and three impervious/pervious surface ratios were assessed on runoff water quality and quantity. A mixed forb/grass prairie and a Kentucky bluegrass (Poa pratensis L.) blend were seeded and runoff was monitored and analyzed for total volume, total P, soluble P, soluble organic P, bioavailable P, total suspended solids, and total organic suspended solids. Mean annual runoff volumes, all types of mean annual P nutrient losses, and sediment loads were not significantly affected by treatments because over 80% of runoff occurred during frozen soil conditions. Total P losses from prairie and turf were similar, averaging 1.96 and 2.12 kg ha(-1) yr(-1), respectively. Vegetation appeared to be a likely contributor of nutrients, particularly from prairie during winter dormancy. When runoff occurred during non-frozen soil conditions turf allowed significantly (P < or = 0.10) lower runoff volumes compared with prairie vegetation and the 1:2 and 1:4 impervious/pervious surface ratios had less runoff than the 1:1 ratio (P < or = 0.05). In climates where the majority of runoff occurs during frozen ground conditions, vegetative buffers strips alone are unlikely to dramatically reduce runoff and nutrient loading into surface waters. Regardless of vegetation type or size, natural nutrient biogeochemical cycling will cause nutrient loss in surface runoff waters, and these values may represent baseline thresholds below which values cannot be obtained.     

Ecological Patterns and Comparative Nutrient Dynamics of Natural and Agricultural Mediterranean-Type Ecosystems

An agricultural watershed, situated on an island of the Aegean archipelago, was studied in order to gain insight into the structure and the design of a typical terrestrial ecosystem of the Mediterranean region. Fieldwork was focused on the comparative study of seasonal patterns of inorganic nutrients, organic nitrogen, and erosion over the most abundant vegetation types of the area, such as olive groves, maquis, and wetlands. Nutrient losses via the pathway of erosion were provided by the determination of nutrient concentrations in runoff sediments. Results showed that nutrient levels are higher and more susceptible to rapid changes in the zones that host agricultural activities and animal husbandry. The behavior of nitrogen and phosphorus showed remarkable stability in the maquis, where dynamic processes were mainly affected by soil erosion, which led gradually to land degradation, especially on sloping terrains. The aim of this study was to form the basis for the quantification of the interconnections within the Mediterranean-type ecosystems and to conceptualize their operational properties.     

Water quality impacts of converting to a poultry litter fertilization strategy

When improperly managed, land application of animal manures can harm the environment; however, limited watershed-scale runoff water quality data are available to research and address this issue. The water quality impacts of conversion to poultry litter fertilization on cultivated and pasture watersheds in the Texas Blackland Prairie were evaluated in this three-year study. Edge-of-field N and P concentrations and loads in surface runoff from new litter application sites were compared with losses under inorganic fertilization. The impact on downstream nutrient loss was also examined. In the fallow year with no fertilizer application, nutrient losses averaged 3 kg N ha(-1) and 0.9 kg P ha(-1) for the cultivated watersheds and were below 0.1 kg ha(-1) for the pasture watersheds. Following litter application, PO(4)-P concentrations in runoff were positively correlated to litter application rate and Mehlich-3 soil P levels. Following litter application, NO(3)-N and NH(4)-N concentrations in runoff were typically greater from cultivated watersheds, but PO(4)-P concentrations were greater for the pasture watersheds. Total N and P loads from the pasture watersheds (0.2 kg N ha(-1) and 0.7 kg P ha(-1)) were significantly lower than from the cultivated watersheds (32 kg N ha(-1) and 5 kg P ha(-1)) partly due to lower runoff volumes from the pasture watersheds. Downstream N and P concentrations and per-area loads were much lower than from edge-of-field watersheds. Results demonstrate that a properly managed annual litter application (4.5 Mg ha(-1) or less depending on litter N and P content) with supplemental N should supply necessary nutrients without detrimental water quality impacts.     

Dry Weather Water Quality Loadings in Arid,Urban Watersheds of the Los Angeles Basin,California, USA1

Abstract: Dry weather runoff in arid, urban watersheds may consist entirely of treated wastewater effluent and/or urban nonpoint source runoff, which can be a source of bacteria, nutrients, and metals to receiving waters. Most studies of urban runoff focus on stormwater, and few have evaluated the relative contribution and sources of dry weather pollutant loading for a range of constituents across multiple watersheds. This study assessed dry weather loading of nutrients, metals, and bacteria in six urban watersheds in the Los Angeles region of southern California to estimate relative sources of each constituent class and the proportion of total annual load that can be attributed to dry weather discharge. In each watershed, flow and water quality were sampled from storm drain and treated wastewater inputs, as well as from in‐stream locations during at least two time periods. Data were used to calculate mean concentrations and loads for various sources. Dry weather loads were compared with modeled wet weather loads under a range of annual rainfall volumes to estimate the relative contribution of dry weather load. Mean storm drain flows were comparable between all watersheds, and in all cases, approximately 20% of the flowing storm drains accounted for 80% of the daily volume. Wastewater reclamation plants (WRP) were the main source of nutrients, storm drains accounted for almost all the bacteria, and metals sources varied by constituent. In‐stream concentrations reflected major sources, for example nutrient concentrations were highest downstream of WRP discharges, while in‐stream metals concentrations were highest downstream of the storm drains with high metals loads. Comparison of wet vs. dry weather loading indicates that dry weather loading can be a significant source of metals, ranging from less than 20% during wet years to greater than 50% during dry years.     

Water Quality Functions of Riparian Forest Buffers in Chesapeake Bay Watersheds

/ Maryland, Virginia, and Pennsylvania, USA, have agreed to reduce nutrient loadings to Chesapeake Bay by 40% by the year 2000. This requires control of nonpoint sources of nutrients, much of which comes from agriculture. Riparian forest buffer systems (RFBS) provide effective control of nonpoint source (NPS) pollution in some types of agricultural watersheds. Control of NPS pollution is dependent on the type of pollutant and the hydrologic connection between pollution sources, the RFBS, and the stream. Water quality improvements are most likely in areas of where most of the excess precipitation moves across, in, or near the root zone of the RFBS. In areas such as the Inner Coastal Plain and Piedmont watersheds with thin soils, RFBS should retain 50%-90% of the total loading of nitrate in shallow groundwater, sediment in surface runoff, and total N in both surface runoff and groundwater. Retention of phosphorus is generally much less. In regions with deeper soils and/or greater regional groundwater recharge (such as parts of the Piedmont and the Valley and Ridge), RFBS water quality improvements are probably much less. The expected levels of pollutant control by RFBS are identified for each of nine physiographic provinces of the Chesapeake Bay Watershed. Issues related to of establishment, sustainability, and management are also discussed.KEY WORDS: Riparian forest buffers; Chesapeake Bay; Nonpoint source pollution; Nitrogen; Phosphorus; Sediment     

Agroforestry practices,runoff, and nutrient loss: a paired watershed comparison

A paired watershed study consisting of agroforestry (trees plus grass buffer strips), contour strips (grass buffer strips), and control treatments with a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation was used to examine treatment effects on runoff, sediment, and nutrient losses. During the (1991-1997) calibration and subsequent three-year treatment periods, runoff was measured in 0.91- and 1.37-m H-flumes with bubbler flow meters. Composite samples were analyzed for sediment, total phosphorus (TP), total nitrogen (TN), nitrate, and ammonium. Calibration equations developed to predict runoff, sediment, and nutrients losses explained 66 to 97% of the variability between treatment watersheds. The contour strip and agroforestry treatments reduced runoff by 10 and 1% during the treatment period. In both treatments, most runoff reductions occurred in the second and third years after treatment establishment. The contour strip treatment reduced erosion by 19% in 1999, while erosion in the agroforestry treatment exceeded the predicted loss. Treatments reduced TP loss by 8 and 17% on contour strip and agroforestry watersheds. Treatments did not result in reductions in TN during the first two years of the treatment period. The contour strip and agroforestry treatments reduced TN loss by 21 and 20%, respectively, during a large precipitation event in the third year. During the third year of treatments, nitrate N loss was reduced 24 and 37% by contour strip and agroforestry treatments. Contour strip and agroforestry management practices effectively reduced nonpoint-source pollution in runoff from a corn-soybean rotation in the clay pan soils of northeastern Missouri.     

Effects of stream channelization on exports of nitrogen and phosphorus from north Carolina coastal plain watersheds

Nitrogen and phosphorus exports from channelizedstream watersheds were elevated over those from nearby natural swamp-stream watersheds. Nitrate exports were significantly greater from channelized-stream watersheds, and higher exports were attributed to faster groundwater drawdown, continual streamflow, and transformation of former floodplain to croplands following channelization. Exports of total organic nitrogen and total nitrogen were also significantly greater from channelized-stream watersheds. Differences in the exports of ammonium, filterable reactive phosphorus, and filterable unreactive phosphorus between the two watershed types were not detectable. Particulate phosphorus exports were significantly higher from channelized-stream watersheds, presumably because of greater erosion potential of nearby croplands and steep channel banks in the altered watersheds. The presence of nonpoint sources of pollution increased watershed exports of nutrients regardless of stream morphology. Examination of nutrient budgets for a portion of swamp floodplain at the base of one natural-stream watershed revealed that changes in local groundwater hydrology and stream morphology associated with channelization appeared to have greater effect on nutrient exports than simply the loss of bordering forested floodplain.     

MUNICIPAL POINT SOURCE AND AGRICULTURAL NONPOINT SOURCE CONTRIBUTIONS TO COASTAL EUTROPHICATION1

ABSTRACT: Tidally influenced reaches of several coastal rivers in eastern North Carolina are suffering from very serious water quality problems — massive surface blooms of noxious blue-green algae, major fish kills from anoxic water, epidemics of red sore disease among fish, fresh water intrusion into estuarine waters, and declining commercial and sports fisheries. An intensive investigation of point source and nonpoint source inputs of nutrients was conducted in one of the eutrophic rivers, the Chowan River. Nonpoint source loading dominated the estimated annual flu of nutrients from the river basin. Automated water quality samplers were utilized to record nutrient levels in stormflow and baseflow from several small agricultural watershed in the basin. Levels of nitrate nitrogen and total phosphorus were from five to 40 times greater in these agricultural watersheds than levels in mostly forested watersheds. Existing water quality data in these eutrophic river basins implicate agricultural activities – particularly animal operations and cropland in watersheds with extensive drainage improvements – as the major contributing factor to the water quality problems.     

MODEL PREDICTIONS OF WATERSHED HYDROLOGIC COMPONENTS: COMPARISON AND VERIFICATIION1

ABSTRACT: Model predictions of the relatively simple soil compartment model SESOIL are compared with those of the more data-intensive terrestrial ecosystem hydrology model AGTEHM. Comparisons were performed using data from a deciduous forest stand watershed, a grassland watershed, and two agricultural field plots. Good agreement was obtained between model predictions for annual values of infiltration, evapotranspiration, surface runoff, and groundwater runoff. SESOIL model predictions also compare well with empirical measurements at the forest stand and the grassland watersheds.     

SOIL CONSERVATION PRACTICES AND WATER QUALITY: IS EROSION CONTROL THE ANSWER?1

ABSTRACT: This paper is a computer simulation analysis of an agricultural nonpoint pollution problem. Computer modeling is a universally applicable tool that can be used for establishing the linkages between and the quality of agricultural runoff in both surface and subsurface flow. The tradeoffs between the costs of soil conservation practices and water quality are reported, and the economic implications of such tradeoffs are discussed. Soil and nutrient losses resulting from crop production practices are analyzed using a field-scale computer simulation model (CREAMS). No-till planting, reduced tillage, and sod waterway systems are more cost effective than other practices for controlling soil and nutrient runoff losses. Nitrate leaching losses are increased slightly by most soil conservation practices. Terrace systems and permanent vegetative cover impose the greatest societal cost for water quality protection. Public cost sharing and tax incentives encourage farmers to adopt expensive structural practices, and policies are needed to get cost-effective practices implemented on critical acreage. Extensive treatment of land is necessary for agricultural best management practices (BMPs) to significantly improve water quality in areas that are intensively farmed.     

NITROGEN AND ORGANIC MATTER LOSSES IN NO‐TILL CORN CROPPING SYSTEMS1

ABSTRACT: Intensive cropping systems based on mechanical movement of soil have induced land degradation in most agricultural areas due to soil erosion and soil fertility losses. Thus, farmers have been increasing fertilization rates to maintain an economically competitive crop yield. This practice has resulted in water quality degradation and lake eutrophication in many agricultural watersheds. Research was conducted in the Patzcuaro watershed in central Mexico to develop appropriate technology that prevents nonpoint source pollution from fertilizers. Organic matter (OM) and nitrogen (N) losses in runoff and nitrate (NO₃‐N) percolation in Andisols with corn under conventional till (CT) and no‐till (NT) treatments using variable percentages of crop residue as soil cover were investigated for steep‐slope agriculture. USLE type runoff plots were used to collect water runoff, while suction tubes with porous caps at 30, 60, and 90 cm depth were used to sample soil water solutes for NO₃‐N analyses. Results indicated a significant reduction of N and OM losses in runoff as residue cover increased in the NT treatments. Inorganic N in runoff was 25 kg/ha for NT without residue cover (NT‐0) and 6 kg/ha for the NT with 100 percent residue cover (NT‐100). Organic matter losses in runoff were 157 and 24 kg/ha for the NT‐0 and NT‐100 treatments, respectively. Nitrate‐N percolation was evident in CT and NT with 100 percent residue cover (NT‐100). However, NT‐100 had higher NO₃‐N concentration at the root zone, suggesting the possibility of reducing fertilization rates with the use of NT treatments.     

OPTIMAL PROFITS UNDER ENVIRONMENTAL CONSTRAINTS: IMPLICATIONS OF NUTRIENT AND SEDIMENT STANDARDS1

To reduce nonpoint source pollution from nutrient, chemical, and sediment runoff, a number of environmental policy standards have been proposed. Such standards could be used to reduce nonpoint source pollution from nutrient, chemical, and sediment runoff to impaired water bodies. State governments can use voluntary approaches to meet nonpoint source pollution reduction goals. However, the practices that lower net returns will not be voluntarily adopted by farmers. Crop rotations and tillage practices may help producers to comply with the environmental standards while minimizing losses in farm profits. This study compares runoff from crop rotation practices and conventional continuous row cropping systems in Mississippi. The results are compared for different tillage systems in order to examine robustness of results. Nutrient runoff and sediment runoff are simulated using the Erosion Productivity Impact Calculator (EPIC). Sensitivity analysis of the sediment and nitrate reductions at 15 percent, 25 percent, and 35 percent are conducted. Under these scenarios, net returns are optimized under environmental constraints, and the marginal cost of sediment reduction ranges from US$1.61 to US$9.63 per ton depending on soil conditions, while the corresponding nitrate and phosphorus reductions costs range from US$1.21 to US$7.08 per kg and from US$0.09 to US$31.91, respectively. The empirical results from this study indicate that a nitrate reduction policy is relatively less costly than a sediment reduction policy. The results also demonstrate the importance of geophysical conditions and policy costs, which vary across regions.     

Role of rainfall intensity and hydrology in nutrient transport via surface runoff

Loss of soil nutrients in runoff accelerates eutrophication of surface waters. This study evaluated P and N in surface runoff in relation to rainfall intensity and hydrology for two soils along a single hillslope. Experiments were initiated on 1- by 2-m plots at foot-slope (6%) and mid-slope (30%) positions within an alfalfa (Medicago sativa L.)-orchardgrass (Dactylis glomerata L.) field. Rain simulations (2.9 and 7.0 cm h(-1)) were conducted under wet (spring) and dry (late-summer) conditions. Elevated, antecedent soil moisture at the foot-slope during the spring resulted in less rain required to generate runoff and greater runoff volumes, compared with runoff from the well-drained mid-slope in spring and at both landscape positions in late summer. Phosphorus in runoff was primarily in dissolved reactive form (DRP averaged 71% of total P), with DRP concentrations from the two soils corresponding with soil test P levels. Nitrogen in runoff was mainly nitrate (NO3-N averaged 77% of total N). Site hydrology, not chemistry, was primarily responsible for variations in mass N and P losses with landscape position. Larger runoff volumes from the foot-slope produced higher losses of total P (0.08 kg ha(-1)) and N (1.35 kg ha(-1)) than did runoff from the mid-slope (0.05 total P kg ha(-1); 0.48 kg N ha(-1)), particularly under wet, spring-time conditions. Nutrient losses were significantly greater under the high intensity rainfall due to larger runoff volumes. Results affirm the critical source area concept for both N and P: both nutrient availability and hydrology in combination control nutrient loss.     

Rate of fall-applied liquid swine manure: effects on runoff transport of sediment and phosphorus

Reducing the delivery of phosphorus (P) from land-applied manure to surface water is a priority in many watersheds. Manure application rate can be controlled to manage the risk of water quality degradation. The objective of this study was to evaluate how application rate of liquid swine manure affects the transport of sediment and P in runoff. Liquid swine manure was land-applied and incorporated annually in the fall to runoff plots near Morris, Minnesota. Manure application rates were 0, 0.5, 1, and 2 times the rate recommended to supply P for a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation. Runoff volume, sediment, and P transport from snowmelt and rainfall were monitored for 3 yr. When manure was applied at the highest rate, runoff volume and sediment loss were less than the control plots without manure. Reductions in runoff volume and soil loss were not observed for spring runoff when frozen soil conditions controlled infiltration rates. The reduced runoff and sediment loss from manure amended soils compensated for addition of P, resulting in similar runoff losses of total P among manure application rates. However, losses of dissolved P increased with increasing manure application rate for runoff during the spring thaw period. Evaluation of water quality risks from fall-applied manure should contrast the potential P losses in snowmelt runoff with the potential that incorporated manure may reduce runoff and soil loss during the summer.     

Modeling watershed-scale effectiveness of agricultural best management practices to reduce phosphorus loading

Planners advocate best management practices (BMPs) to reduce loss of sediment and nutrients in agricultural areas. However, the scientific community lacks tools that use readily available data to investigate the relationships between BMPs and their spatial locations and water quality. In rural, humid regions where runoff is associated with saturation-excess processes from variable source areas (VSAs), BMPs are potentially most effective when they are located in areas that produce the majority of the runoff. Thus, two critical elements necessary to predict the water quality impact of BMPs include correct identification of VSAs and accurate predictions of nutrient reduction due to particular BMPs. The objective of this research was to determine the effectiveness of BMPs using the Variable Source Loading Function (VSLF) model, which captures the spatial and temporal evolutions of VSAs in the landscape. Data from a long-term monitoring campaign on a 164-ha farm in the New York City source watersheds in the Catskills Mountains of New York state were used to evaluate the effectiveness of a range of BMPs. The data spanned an 11-year period over which a suite of BMPs, including a nutrient management plan, riparian buffers, filter strips and fencing, was installed to reduce phosphorus (P) loading. Despite its simplicity, VSLF predicted the spatial distribution of runoff producing areas well. Dissolved P reductions were simulated well by using calibrated reduction factors for various BMPs in the VSLF model. Total P losses decreased only after cattle crossings were installed in the creek. The results demonstrated that BMPs, when sited with respect to VSAs, reduce P loss from agricultural watersheds, providing useful information for targeted water quality management.     

GENERALIZED WATERSHED LOADING FUNCTIONS FOR STREAM FLOW NUTRIENTS1

ABSTRACT: Loading functions are proposed as a general model for estimating monthly nitrogen and phosphorus fluxes in stream flow. The functions have a simple mathematical structure, describe a wide range of rural and urban nonpoint sources, and couple surface runoff and ground water discharge. Rural runoff loads are computed from daily runoff and erosion and monthly sediment yield calculations. Urban runoff loads are based on daily nutrient accumulation rates and exponential wash off functions. Ground water discharge is determined by lumped parameter unsaturated and saturated zone soil moisture balances. Default values for model chemical parameters were estimated from literature values. Validation studies over a three-year period for an 850 km² watershed showed that the loading functions explained at least 90 percent of the observed monthly variation in dissolved and total nitrogen and phosphorus fluxes in stream flow. Errors in model predictions of mean monthly fluxes were: dissolved phosphorus - 4 percent; total phosphorus - 2 percent; dissolved nitrogen - 18 percent; and total nitrogen - 28 percent. These results were obtained without model calibration.     

Capacity of biochar application to maintain energy crop productivity: soil chemistry, sorghum growth, and runoff water quality effects

Pyrolysis of crop biomass generates a by-product, biochar, which can be recycled to sustain nutrient and organic C concentrations in biomass production fields. We evaluated effects of biochar rate and application method on soil properties, nutrient balance, biomass production, and water quality. Three replications of eight sorghum [ (L.) Moench] treatments were installed in box lysimeters under greenhouse conditions. Treatments comprised increasing rates (0, 1.5, and 3.0 Mg ha) of topdressed or incorporated biochar supplemented with N fertilizer or N, P, and K fertilizer. Simulated rain was applied at 21 and 34 d after planting, and mass runoff loss of N, P, and K was measured. A mass balance of total N, P, and K was performed after 45 d. Returning 3.0 Mg ha of biochar did not affect sorghum biomass, soil total, or Mehlich-3-extractable nutrients compared to control soil. Yet, biochar contributed to increased concentration of dissolved reactive phosphorus (DRP) and mass loss of total phosphorus (TP) in simulated runoff, especially if topdressed. It was estimated that up to 20% of TP in topdressed biochar was lost in surface runoff after two rain events. Poor recovery of nutrients during pyrolysis and excessive runoff loss of nutrients for topdressed biochar, especially K, resulted in negative nutrient balances. Efforts to conserve nutrients during pyrolysis and incorporation of biochar at rates derived from annual biomass yields will be necessary for biochar use in sustainable energy crop production.     

Phosphorus forms in biosolids-amended soils and losses in runoff: effects of wastewater treatment process

Continuous addition of municipal biosolids to soils based on plant nitrogen (N) requirements can cause buildup of soil phosphorus (P) in excess of crop requirements; runoff from these soils can potentially contribute to nonpoint P pollution of surface waters. However, because biosolids are often produced using lime and/or metal salts, the potential for biosolids P to cause runoff P losses can vary with wastewater treatment plant (WWTP) process. This study was conducted to determine the effect of wastewater treatment process on the forms and amounts of P in biosolids, biosolids-amended soils, and in runoff from biosolids-amended soils. We amended two soil types with eight biosolids and a poultry litter (PL) at equal rates of total P (200 kg ha(-1); unamended soils were used as controls. All biosolids and amended soils were analyzed for various types of extractable P, inorganic P fractions, and the degree of P saturation (acid ammonium oxalate method). Amended soils were placed under a simulated rainfall and all runoff was collected and analyzed for dissolved reactive phosphorus (DRP), iron-oxide-coated filter paper strip-extractable phosphorus (FeO-P), and total phosphorus (EPA3050 P). Results showed that biosolids produced with a biological nutrient removal (BNR) process caused the highest increases in extractable soil P and runoff DRP. Alternatively, biosolids produced with iron only consistently had the lowest extractable P and caused the lowest increases in extractable soil P and runoff DRP when added to soils. Differences in soil and biosolids extractable P levels as well as P runoff losses were related to the inorganic P forms of the biosolids.     

Subsurface application of poultry litter in pasture and no-till soils

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.