overcoming the challenges of phosphorus-based … and poultry...litter management in poultry...

375NOV | DEC 2007 VOlumE 62, NumbEr 6

Overcoming the challenges of phosphorus-based management in poultry farmingA.N. Sharpley, S. Herron, and T. Daniel

Abstract: Continued economic and use impacts of accelerated eutrophication of fresh waters caused by elevated phosphorus (P) inputs is placing pressure on agriculture to implement P-based nutrient management strategies, particularly for confined animal feeding operations. As P-based strategies usually have a negative impact on farm operations and economics, current challenges are to define where there is a problem and how big of a problem, to determine how to implement and maintain effective best management practices (BMPs), and to identify the best incentives for farmer adoption. These challenges need to be overcome to develop equitable solutions among those affected (i.e., farming, municipalities, and public). The 1997 US Census showed poultry operations had a higher confined animal unit density (3.23 AU ha-1 [1.31 AU ac-1]) than either dairy (0.89 AU ha-1 [0.36 AU ac-1]) or swine operations (0.77 AU ha-1 [0.31 AU ac-1]). This coupled with the generally greater (two- to four-fold) concentration of P in poultry manure than in other livestock type manure makes P-based management especially challenging for poultry operations. Furthermore, because the N:P ratio in poultry litter or manure (3:1) is much narrower than plants generally need (8:1), there is an inherent long-term increase in soil P and thus, potential for runoff P enrichment when manure or litter is applied to meet crop N needs. Even so, the short-term impacts of land-applying poultry manure or litter can be successfully mitigated with adoption of P-based BMPs. These include feed (enzymes, crop hybrids), manure (chemical and physical treatment, composting, transportation), land (amendments, conservation tillage, critical area targeting, buffers, soil testing), and grazing management (duration and intensity, stream bank fencing). However, developing and planning BMPs at farm and watershed scales is not the single or final solution. Many farmers simply do not have the financial resources to imple-ment and maintain costly remedial measures. Despite many programs to help defray remedial costs, institutional red-tape and conflicting requirements often limit program enrollment and hinder widespread adoption. Obviously, there are still challenges, but if affected parties work together, there is a better chance these challenges can be overcome.

Key words: conservation measures—eutrophication—leaching—nutrient management plan-ning—pasture management—poultry litter—remediation—surface runoff—water quality

Andrew N. Sharpley is a professor in the Depart-ment of Crop, Soil and Environmental Sciences at the University of Arkansas in Fayetteville, Arkansas. Sheri Herron is a soil scientist at Her-ron Soil Interpretations in Farmington, Arkansas. Tommy Daniel is a professor in the Department of Crop, Soil and Environmental Sciences at the University of Arkansas, Fayetteville, Arkansas.

Phosphorus (P) has long been recognized as an essential input for plant and ani-mal production. Dramatic improvements in the economic efficiency of grain and animal protein production over the last 50 years have been coupled with an increasing incidence and severity of freshwater eutro-phication (Boesch et al. 2001; Carpenter et al. 1998). Eutrophication is the process of increasing organic enrichment or biological productivity of a water body and is generally accelerated by greater inputs of P (Sharpley

2000). In most cases, eutrophication restricts water use for fisheries, recreation, drinking, and industry due to the increased growth of undesirable algae and aquatic weeds, oxy-

Reprinted from the Journal of Soil and Water Conservation, Volume 62, Number 6. © 2007 by the Soil and Water Conservation Society. All rights reserved.

376 jOurNal Of sOil aND watEr CONsErVatiON

gen shortages, and formation of carcinogens during water chlorination (Burkholder and Glasgow 1997). For water bodies with natu-rally high salt content, as in estuaries, there are likely unique site-specific and seasonal interactions between nitrogen (N) and P that generally limit aquatic productivity (Howarth et al. 2000). In comparison with point sources of P, such as wastewater treat-ment plants and industry, there has been less success in decreasing non-point sources of P, primarily because they are difficult to identify and thus control.

The economic ramifications of nutri-ent enrichment of surface waters, as well as the revision of nutrient management plan-ning strategies at farm and watershed scales to address both P and N management, are profound. For example, both the fishing and tourist industries have been severely affected by harmful algal bloom outbreaks in the Chesapeake Bay and inland waters of the Delmarva Peninsula and North Carolina. Overall, the economic loss to the affected eastern coastal states is estimated at $1 billion over the last two decades (Goodman 1999; Howarth et al. 2000).

In many areas, action agencies have changed their strategic approach to nutri-ent planning with respect to water quality impacts because remediating nutrient sources is less expensive than treating the symptoms of nutrient enrichment. For example, in the early 1990s, New York City decided that identifying and targeting for remediation the sources of P in its water supply watersheds would be more cost-effective than build-ing a new $8 billion water treatment facility (National Research Council 2000). As a result, the state has invested $10 million in identifying and decreasing nutrient sources in its supply watersheds. Increasing water qual-ity concerns associated with greater P inputs has led to farm management nutrient man-agement planning to consider P as well as N (USDA NRCS 2003b). Phosphorus-based nutrient management planning embodies the concept of applying manure or litter to soil based on the P content of the manure and the soil, as well as that needed by crops or forage cover.

Such a strategy is being put in place to target and remediate sources of P in the Eucha-Spavinaw watershed (ESW) in north-west Arkansas and northeast Oklahoma, which collects and supplies water to the metropolitan area of Tulsa, Oklahoma. The

watershed is typical Ozark Highlands with rolling pastures intermixed with wood-land and is densely populated with poultry (broiler) operations, which utilize litter as a fertilizer source for pastures (DeLaune et al. 2004). In 2003, the City of Tulsa and Tulsa Metropolitan Utility Authority reached an agreement with several poultry integrators and the City of Decatur, Arkansas wastewa-ter treatment plant to address allegations that excess agricultural P runoff from pastures fertilized with poultry litter, as well as waste-water discharge from Decatur, were the cause of prolific algae growth and subsequent taste and odor problems in drinking water (US District Court Case No. 01-CV-0900-EA

(C)). The agreement stated that contract poul-try producers in ESW could not land-apply poultry litter until a new P-based nutrient management protocol was developed for use in the entire watershed (DeLaune et al. 2007). A major component of the agreement was to “ensure that nutrient management protocols are used in the watershed to reduce the risk of harm to plaintiffs’ water supply due to land application of nutrients and the City of Decatur’s wastewater treatment plant discharge, while at the same time recognizing the right of the poultry defendants and their producers to continue to conduct poultry operations in the watershed within such pro-tocols and the importance of clean lakes, safe

Figure 1(A) Change in number of confined animals relative to land area available for manure application, and (B) amount of manure phosphorus available for land application as a function of animal type between 1982 and 1997 (adapted from Kellogg et al. 2000).

Conf

ined

ani

mal

s pe

r lan

d ar

ea a

vaila

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for m

anur

e ap

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U h

a–1)

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(kg

P ha

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4

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01982 1987 1992 1997

(A) Animal density

(B) Manure P available for application

Beef cattle

Dairy cows

Swine

Poultry


drinking water and viable poultry industry to the economies of northeast Oklahoma and northwest Arkansas” (DeLaune et al. 2007). Clearly, these P-related nutrient manage-ment issues in several watersheds across the US have raised awareness of the need to meet several challenges facing livestock operations and manure management in particular.

Not all manures are the same, and this presents different challenges for their man-agement. For instance, there are several factors that combine to make manure and litter management in poultry operations more challenging than in dairy and swine operations:

1. From the 1997 US census, poultry operations had higher confined animal units per hectare available for land application of manure (3.23 AU ha-1 [1.31 AU ac-1]) than either dairy (0.89 AU ha-1 [0.36 AU ac-1]) or swine operations (0.77 AU ha-1 [0.31 AU ac-1]) (Kellogg et al. 2000). Further, poul-try operations showed the greatest increase in density between 1982 and 1997 (1.19 to 3.23 AU ha-1 [0.48 to 1.31 AU ac-1]) (figure 1A).

2. Poultry manure tends to have two to four times more P per ton of manure than other livestock types (Kleinman et al. 2005; Sharpley and Moyer 2000).

3. Combination of the above two points result in an appreciably greater amount of P per unit land area for confined poultry than for other livestock operations (figure 1B; Kellogg et al. 2000).

4. Poultry litter is bulkier than other manures leading to greater challenges with application, treatment, and transport.

Clearly, the limited land base available for manure application, high animal density, and large amount of manure P produced on poul-try operations presents more challenges to making P-based nutrient management work than for other types of livestock operations.

Table 1Farming system and phosphorus budget (data adapted from Lanyon 2000 and Bacon et al. 1990).

Nutrient input in feed Nutrient input in fertilizer Output in produce SurplusFarming system (kg P ha–1 yr–1) (kg P ha–1 yr–1) (kg P ha–1 yr–1) (kg P ha–1 yr–1) Nutrient utilization

Cash crop* — 22 20 2 91%Dairy† 30 11 15 26 37%Swine‡ 105 — 30 75 29%Poultry§ 1,560 — 440 1,120 28%* 30 ha cash crop farm growing corn and alfalfa.† 40 ha farm with 65 dairy Holsteins averaging 6,600 kg milk cow–1 yr–1, 5 dry cows, and 35 heifers. Crops were corn for silage and grain, alfalfa and rye for forage.‡ 30 ha farm with 1,280 hogs; surplus includes 36 kg P ha–1 yr–1 manure exported from the farm.§ 12 ha farm with 74,000 poultry layers; surplus includes 180 kg P ha–1 yr–1 manure exported from the farm.

This paper discusses how the evolution of poultry production has shifted the emphasis of P management from one of agronomic to environmental concern. Because of this, we describe how the fate, transport, and man-agement of P in soil and water on poultry farms relates to development of environ-mentally sound best management practices (BMPs) that integrate sustainable stewardship and viability of poultry production systems (figure 2). Finally, we discuss the challenges of making P-based nutrient management on poultry farms work and how the challenges may be overcome.

Evolution of Poultry Systems and Nutrient Management. With the advent of new tech-nologies, mechanization, increased chemical use, and government incentives, agricultural production has more than doubled and has become concentrated on less agricultural land on fewer, but larger, farms (Evans et al. 1996). Also, farming systems have become more specialized, with crop and animal operations efficiently coexisting but in sepa-rate regions of the country, as seen by the switch from crop- to poultry-based systems in several important agricultural states, such as Alabama, Arkansas, Delaware, Maryland, North Carolina, and Oklahoma (Kellogg et al. 2000; Lanyon 2000).

Spatial separation of crop and poultry production systems results in a large-scale, one-way transfer of nutrients from grain- to poultry-producing areas, which broadened the emphasis of nutrient management strate-gies from field to watershed scales (Lanyon 2005; Sharpley et al. 2005). In attempting to balance P at farm and watershed scales, it must be recognized that measures to man-age nutrients at these scales is a complex and interdependent function of strategic planning within the animal industry and market integrators, economic pressures, and consumer demands. These factors are

external to individual farmer decisions, as well as general farm and nutrient man-agement decisions. Thus, it is critical to develop effective remedial strategies that consider not only which practices to use but how to support their implementation and maintenance.

Even so, the potential for P surplus on poultry operations can be much greater than in cropping systems where nutrient inputs become dominated by feed rather than fer-tilizer (table 1). With a greater reliance on imported feeds, only 28% of P in purchased feed for a 74,000 layer operation on a 12 ha (30 ac) in Pennsylvania could be accounted for in farm outputs (table 1). Similar annual surpluses of P were reported for poultry farms in Delaware (Sims 1997) and Arkansas (Daniel et al. 2005).

The already challenging P management implications of intensified poultry operations are exacerbated by their close proximity to P-sensitive waters in these regions (e.g., Neuse River, North Carolina; Chesapeake Bay; Great Lakes; Lake Champlain; Gulf of Mexico; Illinois River, Arkansas and Oklahoma; and North Bosque River, Texas) (Lander et al. 1998; Kellogg et al. 2000).

Fate of Land-Applied Phosphorus in Poultry Operations. The fate of P in typi-cal poultry operations in the United States is shown in figure 3. Typically, less than one-third of feed P is utilized by poultry, with the remainder excreted in manure and applied to land for crop use (Patterson et al. 2005). Phosphorus uptake and harvest removal by crops ranges from 10% to 40% of applied P, due to low crop demand compared to N and the rapid and only slowly reversible sorption of P to Al, Fe, and Ca compounds in soil (fig-ure 3) (Pierzynski and Logan 1993; Sims and Sharpley 2005). Phosphorus loss in surface runoff is generally greater than in subsur-face flow and depends on the rate, time, and


Figure 3Factors affecting the fate of phosphorus in a poultry farm.

Note: Numbers in parentheses are based on an approximate farm nutrient balance and relative fate of P as a percentage of load (farm gate) or percentage of fertilizer and manure (manure application and land management) (adapted from Howarth et al. 2000; Sims and Sharpley 2005).

Farm gateManure application and land management

FeedFertilizer

Animal produce(30% P)

Manure(70% P)

P sorption,immobilization,mineralization

(80%)

P offtake incrop harvest

(15%)

P runoff(5%)

P leaching(1%)

Preferential flowvia macropores

Groundwater

Tile flow

method of P application; the form of fer-tilizer or manure applied; and amount and time of rainfall after application (Sharpley

and Rekolainen 1997). Leaching of P can occur in sandy, organic, or peaty soils—those with low P adsorption capacities; and in soils

with substantial preferential flow pathways (Bengston et al. 1988; Sharpley and Syers 1979; Sims et al. 1998) (figure 3). Overall,

Figure 2Best management practices that minimize phosphorus loss from poultry farming systems.

Management of P in feedand use of enzymescan enhance nutrientutilization and decreaseexcretion

Manure amendmentand compostingcan reduce P solubility

Appropriate method and timingof manure application increasescrop uptake

Conservation tillagedecreases P runoff

Soil and manure testing for Pcan help tailor appropriatemanure rates to apply

Subsurface applicationof manure decreases P runoff

Pasture regenerationincreases soil infiltrationand decreases runoff

Riparian bufferstrap particulate P and takeup some dissolved P

Stream bank fencingexcludes animals anddecreases direct deposition of P in streams


Figure 4Surface soil (0 to 5 cm) Mehlich-3 P and mean annual dissolved P concentration of surface runoff and subsurface flow (70 cm depth) from bermudagrass before, during, and after poultry litter application (11 Mg ha–1 yr–1; 140 kg P ha–1 yr–1).

Meh

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(mg

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250

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5

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Melich-3 P

Surface runoff P

Subsurface flow P

1989 90 91 92 93 94 95 96 97 98 1999

No litterapplied

Poultry litter applied

140 kg ha–1 yr–1

No litter applied

P loss is agronomically small (generally <2 kg P ha-1 [<1.75 lb P ac-1]), representing a minor proportion of P applied as fertilizer or manure (generally <5%).

The effect of poultry litter applications to bermudagrass (Cynodon dactylon) plots (16 m2 [172 ft2]) in southeastern Oklahoma on P in soil, loss in surface and subsurface (70 cm [28 in] soil depth), and crop uptake was evaluated for 10 years (Heathman et al. 1995; Sharpley 1999). Application of poultry litter (11 Mg ha-1 [5 tn ac-1]; 140 kg P ha-1 [125 lb P ac-1]) to a Ruston fine sandy loam soil (Typic Paleudult) for three years increased Mehlich-3 in the surface soil from 10 to 258 mg kg-1 (figure 4). Prior to litter application, the mean average dissolved P concentra-tion of surface runoff averaged 0.08 mg L-1, increasing to 2.93 mg L-1 the first year of application (1991) and to 4.08 mg L-1 in 1993 (figure 4). When litter application was stopped, there was an immediate decrease in surface soil Mehlich-3 and mean annual dis-solved P concentration (figure 4).

The dissolved P in subsurface flow at a depth of 70 cm (28 in) also increased with litter application, albeit more slowly than in surface runoff after litter was added, peaking in 1994 (1.18 mg L-1). Despite the increase in subsurface flow P with litter application, there was no significant increase in Mehlich-3 P below 20 cm (8 in) in the soil, suggesting the importance of preferential flow (e.g., via macropores, earthworm holes, and old root channels) as a potential pathway for P loss. Hence, the lack of any accumulation of soil P in a subsoil does not preclude the fact that some P may be moving though the profile.

At the end of each growing season, bermudagrass yield and P content were determined and P uptake calculated (table 2). The loss of total P in surface and subsurface flow during each flow event was calculated as the product of total P concentration and flow volume, and a simple annual P budget was determined from the input of P in litter and output in bermudagrass harvest, surface runoff and subsurface flow (table 2). Prior to litter application there was a negative P bal-ance, with about 7 kg P ha-1 yr-1 (6 lb ac-1 yr-1) removed from the plot (table 2). When litter was applied, there was a surplus of 116 kg P ha-1 yr-1 (104 lb ac-1 yr-1). Over the 11-year study, there was a total P surplus of 206 kg P ha-1 yr-1 (184 lb ac-1 yr-1) (table 2). Applying litter to meet the N requirements of bermudagrass for three years, resulted in

applying 365 kg P ha-1 (326 lb ac-1) that was not removed by bermudagrass, which clearly results in an increase in runoff P loss.

After six years (1994 to 1999), Mehlich-3 soil P had declined to 192 mg kg-1, surface runoff had dissolved P to 0.52 mg L-1, and subsurface had dissolved P to 0.22 mg L-1. These soil test P levels are still appreciably greater than local fescue crop requirements (20 to 60 mg kg-1) and surface water thresholds associated with accelerated eutro-phication (0.02 to 0.05 mg L-1).

Phosphorus-Based Nutrient Management MeasuresPhosphorus-based nutrient management embodies a wide array of measures and concepts related to environmentally sound stewardship and sustainable P use. The USDA Natural Resources Conservation Service (NRCS) has developed National Conservation Practice Standards for nutri-ent management plus various other BMPs. Those related to P are listed in table 3 (USDA NRCS 2003a). These measures can be grouped into those related to the management of feed, manure, land, and grazing (table 3). We include grazing in this discussion as beef rearing on pastures is an integral part of many poultry farms in the United States.

Feed Management. Feed management aims

to reduce the amount of P imported onto poultry farms by decreasing mineral P sup-plements in feed, including enzymes in feed that enhance nutrient utilization and absorp-tion by poultry, and use of crop hybrids that contain lower levels of relatively indigestible phytate-P (table 3). However, with inte-grated poultry production, feed ingredients are controlled by integrator companies such that individual farmers have few options for dietary or feed manipulation.

Feed supplements: Supplementing poultry diets with enzymes to enhance the digestion of feedstuffs can decrease the quantity of P excreted. For instance, adding amino acids and phytase to the diet of laying hens can reduce P excretion almost 50%, although this nearly trebled diet cost ($342 t-1 (305 tn-1) compared to $126 t-1 (113 tn-1) for the con-trol diet) (Keshavarz and Austic 2003). As a significant portion of P in corn grain is of low digestibility, feed is supplemented with mineral P which contributes to P enrich-ment of manures and litters. Supplementing feed with enzymes such as phytase that break down phytate into digestible forms reduces the need for P supplements and can decrease the total P content of manure (Maguire et al. 2005). However, the jury is still out as to whether land application of manure or litter from poultry fed phytase translates into decreased losses of P in runoff, unless


litter application is P-based (DeLaune et al. 2001; Moore et al. 1998; Penn et al. 2004). Some have attributed the lack of any effect of dietary phytase on decreasing runoff P, to the possible excretion of microbes continuing to solubilize both manure and soil P (Ajskaiye et al. 2003; Angel et al. 2005).

Corn hybrids are also available which contain low amounts of indigestible phytate P. Poultry fed “low-phytic acid” corn grain excreted less P in manure than those fed conventional corn varieties (Ertl et al. 1998). Currently, the challenge to plant breeders is to incorporate the low-phytate trait into other crops, such as soybeans, because of greater pressures being placed on corn for biofuel production.

Manure Management. Manure and litter can be managed to decrease P solubility with chemical amendments and physical treat-ment, development of alternative uses for manure or litter other than land application, and transport of manure and litter further from where it is produced (table 3).

Manure amendments: Commercially available manure amendments, such as slaked lime or alum, are used to reduce NH3 volatilization in poultry barns, leading to improved animal health and weight gains. Coincidentally, these amendments reduce the solubility of P in poultry litter and when land applied, the dissolved P concentrations in surface runoff (Moore et al. 2000; Shreve

et al. 1995). Perhaps the most important benefit of manure amendments for both air and water quality is to affect an increase in the N:P ratio of manure, via reduced N loss from NH3 volatilization, which more closely matches crop requirements.

Bioenergy: One of the potential end uses of excess manure transported off farms is as a source of “bioenergy.” For example, dried poultry litter can be burned directly or converted by pyrolytic methods into oils suitable for use to generate electric power (MacDonald 2007). This could be at the scale of contributing to rural power networks or to on-farm supplemental energy supplies (Codling et al. 2002; Costello and Roe 2004). As the cost of conventional fuel continues to rise and as the cost and supply of poultry lit-ter is relatively stable, burning litter will be a viable approach to power generation. This process reduces the volume of manure that needs to be managed and produces a P- and K- rich ash that has potential fertilizer value. As the value of clean water and cost of sus-tainable manure management is realized, we can expect that other entrepreneurial uses for manure will be developed, will become more cost-effective, and thus, will create expanding markets.

Composting: Composting may also be considered as a management tool to improve manure distribution because composting makes manure more physically and chemi-

cally uniform, which facilitates even spreading at accurate rates (Day and Funk 1998; Osei et al. 2000). Although composting tends to increase the P concentration of manure, the volume is reduced, thus decreasing transpor-tation costs. Manure can also be used along with biosolids and woodchips to reclaim soils that have been disturbed, for example, by mining and urban construction. In these cases, manure and litter can be used as an excellent soil conditioner for the reclamation of mine sites, urban lawn improvements, and major developments where topsoil or subsoil conditioning is needed.

Physical treatment: Sieving to separate fine and coarse fractions may increase man-agement options for manures such as poultry litter. While P and K are uniformly distrib-uted throughout the litter, the concentration of N is commonly greatest in the fine frac-tion, which results in an increase in the N:P ratio of that fraction (Ndegwa et al. 1991). A larger N:P ratio is desirable because the N:P ratio in unfractionated poultry litter is much smaller than that required by plants.

Transport: In many areas, manure is rarely transported more than ten miles from where it is produced. As a result, manure is often applied to soils that already have suf-ficient nutrients to support crop growth. Mechanisms need to be established to facili-tate movement of manure from surplus to deficit areas. An increasing number and vari-

Table 2Phosphorus budget of poultry litter application, phosphorus uptake by bermudagrass, and total phosphorus loss in surface and subsurface flow from a Ruston fine sandy loam in Oklahoma.

Bermudagrass TotalPlossinflow

Litter P added Yield P uptake Surface SubsurfaceYear (kg ha–1 yr–1) (kg ha–1 yr–1) (kg ha–1 yr–1) (kg ha–1 yr–1) (kg ha–1 yr–1) P balance

Before application1989 0 3,500 5.9 0.2 0.1 –6.21990 0 4,010 6.4 0.2 0.1 –6.7During application1991 140 8,110 16.9 3.8 0.1 +119.21992 140 8,210 18.6 5.1 0.4 +115.91993 140 8,510 20.0 7.8 0.5 +111.7After application1994 0 8,040 22.5 5.6 0.7 –28.81995 0 7,120 18.2 4.2 0.6 –23.01994 0 6,920 15.2 2.2 0.5 –15.91997 0 7,510 19.2 1.6 0.4 –21.21998 0 7,230 18.7 1.3 0.2 –20.21999 0 6,900 17.4 0.9 0.2 –18.5Total 420 76,060 179.0 32.9 3.8 +206.0Notes: Balance of P was determined as litter P added – P uptake by grass +P loss in surface runoff + P loss in subsurface flow. Negative values indicate a net loss of P from the plots and positive values a net gain of P.


Table 3Measures to control nonpoint sources of phosphorus from poultry operations.

ImpactPractice Description on P loss Conservation practice code*

Animal feed managementCrop hybrids Low phytic-acid corn decreases P in manure Decrease 592Feed additives Phytase enzyme increases P utilization by animal Decrease 592Feed supplements Match poultry nutritional requirement Decrease 592

Manure managementApplication method Incorporated or subsurface injection Decrease 370, 590, 633Application rate Match crop/pasture needs Decrease 633Application timing Apply during season with low runoff probability Decrease 370, 590Amendment Adding alum to manure decreases P solubility Decrease 359, 370, 590, 591Bioenergy Specially designed power plants fueled by poultry litter Decrease —Composting Increases bulk density and uses for manure Decrease 317Manure stacking Lengthens the window of time for land application Decrease 313, 367Transfer Move manure from area with surplus to deficit nutrients Decrease 634

Land managementConservation cover Permanent vegetative cover increases soil infiltration and Decrease 327 water holding capacityConservation tillage Reduced and no-till increases infiltration and decreases Decrease TP, soil erosion and total P loss Increase DP 329, 344, 345, 346Cover crops/residues If harvested can reduce residual soil P Decrease TP, 340 Increase DPCritical source area treatment Target sources of P in a watershed for remediation Decrease 590Invert stratified soils Redistribution of surface P through profile by deep tillage Decrease 324Riparian, buffer, wetland areas Removes sediment-bound P Decrease TP, 332, 393, 391, 412, 601,607, Neutral DP 608, 612, 646, 658Soil P testing Applications based on soil P availability and crop P needs Decrease 590Soil amendment Flyash, Fe oxides, gypsum decrease P solubility Decrease 590Strip cropping, contour tillage, terraces Decreases transport of sediment-bound nutrients Decrease TP, 330, 585, 600, 660 Neutral DP

Grazing managementPasture renovation Increases soil aeration and infiltration Decrease 512, 528, 561Stream bank fencing Decreases direct deposition of P and bed erosion in stream Decrease 382, 472, 578, 580Watering facilities Decreases direct deposition of P and bed erosion in stream Decrease 574, 614* USDA NRCS National Conservation Practices Standard Codes from http://www.nrcs.usda.gov/technical/Standards/nhcp.html.Notes: TP is total phosphorus, and DP is dissolved phosphorus.

ety of programs are coming into existence to meet the needs of poultry farmers to move manure across farm, county and even state boundaries. Responding to the restric-tions on land application of poultry litter in the ESW, as a result of a lawsuit settlement agreement, poultry producers are using the services of brokers to arrange for the sale and transport of their litter to crop producers. As an example, BMPs Inc., a non-profit corpo-ration, was established by representatives of five poultry integrator companies to assist in litter export. BMPs Inc. coordinates broiler house clean-out, litter hauling, and spread-ing of litter for poultry producers and litter buyers. This broker currently serves poul-try producers, litter buyers and haulers in

Arkansas, Oklahoma, Missouri and Kansas, as well as managing federal grants for Arkansas and Oklahoma that offset a portion of the hauling costs and pay the producers for their litter. Such brokers will provide increasingly valuable services to poultry producers and crop producers, while establishing a sustain-able system for the future.

The concept of poultry litter brokers and banks has grown to meet the needs of lit-ter buyers who have signed up for subsidized programs and are requesting a “turn-key coordination process,” similar to that used to obtain commercial fertilizer. Crop producers purchasing litter want to be able to contact a broker, order litter to be delivered and have it spread on their fields. On the other

hand, poultry producers need the security of knowing their houses will be cleaned in a timely manner and that they will receive compensation for the P and N sold in their litter. In the case of the ESW, brokers have been successful at facilitating the movement of 80% of the poultry litter produced out of the watershed, rather than have it continued to be applied in the ESW.

Land Management. Land management aims to decrease the potential for P loss in surface and subsurface runoff by use of risk assessment indices to guide the rate, method and timing of poultry manure or litter appli-cation, and by targeting critical source areas of P loss for BMP implementation (table 3).

Soil amendments: As a result of Clean Air


legislation, large amounts of coal combus-tion by-products (CCBs) are being produced annually by power plants (US Environmental Protection Agency 1988). Previous research has shown that these types of CCBs can be safely used to increase soil pH and decrease subsoil acidity (Callahan et al. 2002; Stout et al. 1999; Stout and Priddy 1996). Recent research has also shown that two of these CCBs, fluidized bed combustion flyash and flue gas desulfurization gypsum, can greatly decrease water soluble P levels in soils and surface runoff without appreciably decreas-ing plant available P and plant growth or increasing heavy metals and arsenic in plants or runoff waters (Stout et al. 1998; Stout et al. 2000). Use of these amendments on criti-cal areas of a watershed has the potential to make large albeit short-term reductions in P loss (Stout et al. 1999).

Critical source area management: Transport mechanisms determine whether P sources are translated from being a resource to a loss. Phosphorus loss generally occurs from hydrologically active areas of the water-shed where surface runoff contributing to stream flow is coincident with areas of high soil P (Gburek and Sharpley 1998; Gburek et al. 1996). This is supported by Pionke et al. (2000), who showed that up to 80% of annual P loss comes from <20% of the land area in hill-land watersheds. These areas are hydrologically connected to streams and tend to be within 60 m of the channel (Gburek and Sharpley 1998). Runoff and P can be decreased or even intercepted by infiltration and deposition, respectively, prior to reach-ing a stream channel. Generally, the closer a field is from a stream channel, the greater the potential for runoff to contribute P to the stream. Thus, many states have adopted the premise of implementing more restrictive management for fields close to a stream than for fields further away (Sharpley et al. 2003).

Even in regions where subsurface flow pathways dominate, areas contributing P to drainage waters appear to be restricted to soils with high soil P saturation and hydro-logic connectivity to the drainage network. For example, Schoumans and Breeuwsma (1997) found that soils with high P saturation contributed only 40% of total P load, while a further 40% came from areas where soils have only moderate P saturation but some degree of hydrological connectivity with the drain-age network. It is likely that integration of spatial technology, such as global positioning

Figure 5As soil phosphorus increases so does crop yield and the potential for P loss in surface runoff.

Note: The interval between the critical soil P value for yield and runoff P will be important for P management.

)

)

)

)

Rel

ativ

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op y

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ss in

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Soil test P categories for potential P loss in runoff

Soil test P categories for crop yield response

Low Optimum High

Low Medium High

Criticalvalue

for P loss?

The “gap”

Criticalvalue

for yield

systems, remote sensing, geographical infor-mation systems, and site measurement related to soils, crops, and nutrient management will help target BMPs across watersheds (Berry et al. 2005). These tools can evaluate in time and space how BMPs contribute to decreas-ing P loss at field and watershed scales (Berry et al. 2003). Future development of precision conservation tools could help critical source area management to reduce P loss.

Riparian/buffer areas: As well as reducing P export, riparian areas can increase wildlife diversity and aquatic habitat. In addition to acting as physical buffers to sediment-bound P, plant uptake captures P, resulting in a short-term and long-term accumulation of P in biomass (Groffman et al. 1992; Peterjohn and Correll 1984; Uusi-Kamppa 2000). A paired-watershed study in Connecticut was used to evaluate the effect of a 30-m (98-ft) ripar-ian buffer of fescue (with woody species near the stream edge) adjacent to a field of corn silage (Clausen et al. 2000). Concentrations of total P in surface runoff were reduced by 73%. Another paired-watershed study con-ducted in Vermont was used to evaluate the effectiveness of field-edge buffers of mixed grass-legume (7.5 and 15 m [25 and 49 ft] widths) in minimizing nutrient losses in runoff from a corn field (Jokela et al. 2004). Preliminary results show significant reduc-

tions in total P in runoff with implementation of a 15 m mixed grass-legume buffer.

The effectiveness of conservation buffer areas can vary significantly. For instance, the route and depth of subsurface water flow paths though riparian areas can influence P retention. Conservation buffers are most efficient when sheet flow occurs rather than channelized flow, which often bypasses some of the retention mechanisms. Thus, these areas must be carefully managed to realize their full retention and filtration capabilities.

Soil testing: As we move from agronomic to environmental concerns with P, soil P testing is being used to indicate when P enrichment of runoff may become unac-ceptable. As the use of P-based nutrient management recommendations expand, attention has focused on the paucity of information linking soil P with the poten-tial for P loss. Because of this, a common approach has been to use agronomic soil P standards, following the rationale that soil P in excess of crop requirements is vulnerable to removal by surface runoff or leaching. As agronomic standards already exist for soil test P, this approach required little investment in research and development and can be readily implemented. However, we must be careful how we interpret soil test results for environ-mental purposes (figure 5).


Interpretations given on soil test reports (i.e., low, medium, optimum, high, etc) are based in the expected crop yield response to P and not on soil P release to surface or sub-surface runoff (Sharpley et al. 1994). Some have tried to simply extend crop response levels and say that a soil test that is above the level where a crop response is expected is in excess of crop needs and therefore in poten-tially polluting (figure 5). Although research has shown conventional crop response soil P tests can estimate a soils’ potential to enrich runoff with P, this relationship is neither direct nor quantitative (Daverede et al. 2003; Pierson et al. 2001; Torbert et al. 2002; Vadas et al. 2005). Two factors are of critical impor-tance to the debate on how to use soil test P in environmental risk assessment. Firstly, the gap between crop and environmental soil P thresholds reflects the difference in soil P removed by an acid or base extractant (i.e., Mehlich, Bray, and Olsen agronomic tests) and by less invasive water (i.e., environmen-tal test), which is soil specific. Secondly, soil P is only one of several factors influencing the potential for P loss; soil test P should not be used as the sole criteria for environmentally based P management planning.

Grazing Management. Intensity and dura-tion of grazing: As beef grazing of pastures is an integral component of poultry opera-tions in many regions of the United States, careful management is needed to minimize P from cattle and applied litter. Localized accumulations of P where manure is depos-ited can saturate the P sorption capacity of a soil, increasing the potential for P loss from grazed pastures in runoff or drainage waters (Breeuwsma et al. 1995; Nelson et al. 1996). At field and watershed scales, critical stock-ing factors, such as density and duration will influence both hydrologic and chemical fac-tors controlling P transport. For example, Owens et al. (1997) found that rotational grazing (25 Charolais beef cows on a 1.1 ha [3 ac] pasture) from May through October dramatically reduced runoff (88%) and ero-sion (94%) from a pastured watershed in Ohio compared with continuous year-round grazing, which should lower the potential for P loss. Olness et al. (1975) found that P loss was greater from continuously grazed pas-tures (4.6 kg ha-1 yr-1 [4.1 lb ac-1 yr-1]) rather than rotationally grazed pastures (1.3 kg ha-1 yr-1 [1.2 lb ac-1 yr-1]). In contrast, P loss with continuous grazing was greater than from

alfalfa or wheat (2.7 kg ha-1 yr-1 [2.4 lb ac-1 yr-1]) (Olness et al. 1975).

There will probably be a critical stocking impact above which further compaction by animals will reduce infiltration sufficiently to dramatically increase runoff susceptibility and, thus, P loss. For instance, Sharpley and Syers (1976, 1979) found grazing increased surface runoff (40%) (figure 6), while reduc-ing tile discharge (70%). Although rainfall varied before and after grazing, hence the difference in flow among runoff events, comparison between grazed and ungrazed pastures allowed quantification of grazing effects. The study area was grazed at a stock-ing rate of 25 dairy cattle ha-1 (10.12 AU ac-1) for 24 hours at the beginning of August, as part of the normal grazing plan for the farm. Before grazing, discharge from both fields was similar (figure 6A). In the first runoff event one week after grazing, surface runoff was appreciably greater from the grazed than ungrazed plot (figure 6B). Discharge from the grazed field was still greater than that from the ungrazed field three weeks after grazing (figure 6C). The increase in surface runoff and reduction in tile drainage can be attributed to the disruption of macropores at the top of the soil profile and to surface “pugging” or compaction, which reduced infiltration capacity and preferential flow.

Grazing increased dissolved P concentra-

tions in both surface runoff and tile drainage one day after grazing, with maximum values (1.89 mg L-1 [1.89 ppm] in surface runoff and 0.29 mg L-1 [0.29 ppm] in tile drain-age) attained after only one week (figure 7; Sharpley and Syers 1976, 1979). Over the three-year study, periodic grazing increased surface runoff (1,400 to 1,970 m3 ha-1 yr-1 [1,250 to 1,759 lb ac-1 yr-1]), erosion (280 to 1,190 kg ha-1 yr-1 [250 to 1,063 lb ac-1 yr-1]), dissolved P loss (0.35 to 0.82 kg ha-1 yr-1 [0.31 to 0.73 lb ac-1 yr-1]), and total P loss (1.15 to 2.50 kg ha-1 yr-1 [1.03 to 2.2 lb ac-1 yr-1]).

Stream-bank fencing: By observing four pastured dairy herds with stream access over four intervals during the spring and sum-mer of 2003 in the Cannonsville watershed south central, New York, James et al. (2006) were able to estimate fecal P contributions to streams. They observed cattle were especially likely to defecate in the stream, although they spent only a small proportion of their time there. On average, approximately 30% of all fecal deposits fell on land within 40 m (131 ft) of a stream and 7% fell directly into streams (James et al. 2006). Although water troughs, feeders, salt, and shade located away from the stream did affect where cattle con-gregated, the stream was a consistent draw. Using spatial databases of streams, pasture boundaries, and livestock characteristics (i.e.,

Figure 6Surface runoff from ungrazed and grazed fields on a dairy farm, Palmerston North, New Zealand, from three rainfalls: (A) one week before grazing, (B) one week after grazing, and (C) three weeks after grazing (adapted from Sharpley and Syers 1976).

Surf

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number of cattle, time in pasture, and type of cattle [heifers vs. milk cows]) for 90% of the dairy farms in the Cannonsville watershed, approximately 3,600 kg (3.5 tn) of manure P were estimated as deposited directly into streams with 7,650 kg (7.5 tn) deposited in pasture near streams (<10 m [<33 ft]) from the 11,000 dairy cattle in the watershed (James et al. 2006). This equates to approxi-mately 12% of watershed-level P loadings attributed to agriculture (Scott et al. 1998).

Riparian shade can also attract grazing cattle and influence P loss in stream flow. Byers et al. (2005) found that 0.3 kg ha-1 yr-1

(0.3 lb ac-1 yr-1) dissolved P and 1.2 kg ha-1 yr-1 (1.1 lb ac-1 yr-1) total P were exported in stream flow over three years from a 14.2 ha (35 ac) tall fescue and bermudagrass water-shed grazed by 20 cows in Eatonton, Georgia, with 1.8 ha (4 ac) of non-riparian shade. In comparison, 0.6 kg ha-1 yr-1 (0.5 lb ac-1 yr-

1) dissolved P and 4.6 kg ha-1 yr-1 (4.1 lb ac-1 yr-1) total P were exported in stream flow from a 17.5 ha (43 ac) watershed with only 0.6 ha (1 ac) of non-riparian shade. Byers et al. (2005) concluded that as both watersheds had similar areas of unfenced riparian shade (0.5 ha [1 ac]), the greater area of nonriparian

shade attracted cattle which spent less time in the stream and resulted in a twofold reduc-tion in dissolved and fourfold reduction in total P export.

Recent efforts to exclude cattle from streams as part of the Conservation Reserve Enhancement Program (CREP) are esti-mated to have resulted in a 32% decrease in P loadings to streams within the Cannonsville watersheds (James 2005). Thus, exclusionary programs like CREP and stream bank fenc-ing are working to reduce nutrient loading by fencing cattle out of the stream and adjacent riparian zones. Clearly, grazing management and placement of stream bank fencing is important to minimizing watershed export of P. For instance, herd size, pasturing time, and cattle type could all be used to prioritize sites for fence installation. In addition, field observations by James et al. (2006) show that simply installing alternative water sources does not necessarily preclude continued use of streams as a preferred source of water.

Nutrient Management Planning for Poultry OperationsSeveral studies have shown some water quality benefits of having and following a nutrient management plan in livestock oper-ations (Beegle 2005; USDA NRCS 2003b; Nowak and Cabot 2004; Shepard 2005). Meals (1990) and Jokela et al. (2004) reported some improvement in Lake Champlain water quality as a result of decreased P inputs following implementation of BMPs in the watershed. However, there is less informa-tion on the barriers to overcome in poultry operations before lasting improvements in water quality can be realized. These barriers involve the development, acceptance, imple-mentation, and assessment of the nutrient management process.

Plan Development and Implementation. The process of nutrient management plan-ning is of particular importance to poultry farmers, who tend to operate with a small land base (<40 ha [<99 ac]) (Kellogg et al. 2000). These farmers often turn to confined animal operations to supplement inadequate cash returns on traditional grain and forage pro-duction due to local conditions of inherent low soil fertility, erratic rainfall, and reduced crop prices. Therefore, the need for P inputs to local cropping systems will be lower than in areas of intensive crop or forage production.

The cost of implementing Comprehensive Nutrient Management Plans (CNMPs) on

Figure 7Mean dissolved P concentration in surface runoff and tile drainage before and after grazing on a dairy farm, Palmerston North, New Zealand (adapted from Sharpley and Syers 1976, 1979).

Surface runoff

Ungrazed control

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the 257,200 farms identified in the 1997 Census of Agriculture as needing a plan is estimated to be $17.4 billion over the 10-year implementation period (USDA NRCS 2003b). This is an average $6,748 for each farm and reflects the cost needed to install, modify, and upgrade practices and struc-tures required by the CNMP. To offset these costs to a certain extent, innovative measures are being taken to encourage the imple-mentation and maintenance of BMPs as part of a required CNMP. For example, the Cannonsville Watershed, New York recently implemented a nutrient management enhancement program in which farmers who follow an approved CNMP are given finan-cial credits each year (Watershed Agricultural Council 2004). These credits can be used to purchase or upgrade equipment that would need to be used to implement the plan, such as manure spreaders, injectors, etc.

Plan Adoption. James (2005) recently conducted a survey of farmers in the Cannonsville watershed, New York, on voluntary participation in CREP for improvement in water quality by limit-ing crop production, hay harvesting, and livestock use in sensitive riparian areas and stream corridors. The survey showed CREP participants were generally older and more likely to obtain information from extension agents, consultants, etc., but there was no difference in education level or farming status (full or part time) between partici-pants and non-participants. Overall, negative responses to voluntary enrollment in BMP adoption focused on the loss of productive land and loss of being able to decide inde-pendently what to do on their own land (James 2005). This survey illustrates the com-plexities of adopting nutrient management BMPs among farmers in any given water-shed, complexities that are related not only to the transfer of new BMP technology but to socioeconomic pressures.

There are several sources of technical assistance and financial cost-share and loan programs to help defray plan adoption costs. Despite this, the large number of local, state, and federal agencies a farmer has to deal with can be daunting and can discourage adop-tion of the program and implementation of some BMPs. For example, installation of stream bank enhancement and fencing as part of CREP requires the farmer to interact with, among others, NRCS, the US Fish and Wildlife, state department of environmental

protection, US Army Corps of Engineers, and US Environmental Protection Agency to obtain approval at various stages in the plan-ning process.

Plan Assessment. Does P-based manage-ment work? Most importantly, there has been little coordinated field evaluation of P-based BMPs on a watershed scale, in addition to edge-of-field assessment of individual BMPs, to show where, when, and which work most effectively to minimize P loss. There needs to be a concerted effort to demonstrate to the farming community and public that adoption of appropriate BMPs in the right place in a watershed will result in an improvement in water quality. Research is also needed to eval-uate the spatial and temporal variability in a system’s response to BMP implementation. This will allow us to answer critical questions such as how long before we see an environ-mental response and where would we expect to observe the greatest or least response?

Insight into how successful implementa-tion of nutrient management planning has been in reducing P applications was pro-vided by a survey of 127 dairy farms (90% of all farms) in two watersheds in northeastern Wisconsin (Shepard 2005). Shepard (2005) found that farmers with a nutrient man-agement plan (53% of farms) applied less P (31 kg ha-1 [28 lb ac-1]) than farms without a plan (44 kg P ha-1). This study showed that although having a nutrient management plan reduced P applications, more emphasis needs to be placed on crediting manure as an on-farm P source. For example, only half the farmers with nutrient management plans in the Wisconsin watersheds surveyed actually credited on-farm manure P, and only 75% fully implemented their plan on the major-ity of acres it covered (Shepard 2005). This study survey reinforces our contention that successful P-based nutrient management planning, in terms of bringing about water quality improvements, can only be achieved if technical assistance programs focus on plan implementation and maintenance, rather than achieving goals set for the number of plans written in a given period.

Even so, questions still remain as to whether P-based nutrient management, particularly on farms land-applying manure, will actu-ally decrease soil and runoff P levels and how long is will be before significant decreases are seen, especially to levels below water qual-ity thresholds. Continuing research on the Eastern Shores of Maryland is evaluating the

effect of manure management planning strat-egies on soil and runoff P from an Othello silt loam (fine-silty, mixed, active, mesic Typic Endoaquults) under a corn-soybean rotation that had received poultry litter for the last 20 years and as a result had high soil test P (~400 mg kg-1 as Mehlich-3 P) (Sharpley et al. 2004). Manure management strategies are N-based, where litter is applied to meet crop N requirements (40 to 116 kg P ha-1 yr-1 [36 to 104 lb P ac-1 yr-1]); P-based, where litter is applied to supply crop P uptake (20 to 58 kg P ha-1 yr-1 [18 to 52 lb P ac-1 yr-1]); and soil test P threshold, where no litter is applied as Mehlich-3 P was >75 mg kg-1 (75 ppm) for P-based and soil test P threshold treatments, anhydrous ammonia fertilizer was also added to supplement crop N requirements.

Although the loss of dissolved and total P in surface runoff increased each year as the three strategies were implemented due to increased annual rainfall and runoff vol-umes, the effect of P-based and soil test P strategies on decreasing P loss compared to N-based was evident after three years (i.e., by 2002) (table 4). In the fifth year after plan implementation, dissolved and total P losses were a respective 83% and 80% lower from the soil test P than N-based approach (table 4). Over the same time, surface soil (0 to 5 cm [0 to 2 in] depth) Mehlich-3 P decreased only with the soil test P based litter application (401 to 320 mg P kg-1) (figure 8). As a consequence, corn and soybean yields were not affected by any management approach (table 4).

This research shows that implementation of P-based manure management strategies, whether it be applying manure to match crop P offtake or no manure at all, can decrease runoff P. Nevertheless, it took three years for the effect of these approaches to become evi-dent at this Coastal Plains site on the Eastern Shores of Maryland (Sharpley et al. 2004). Even five years after implementing changes, both mean annual total P concentrations (1.85 and 1.07 mg L-1 for P-uptake and soil test P-based approaches) in runoff and sur-face soil (488 and 320 mg kg-1 for P-uptake and soil test P-based approaches) were still above respective environmental thresholds for flowing waters and soils (0.05 mg L-1 for total P and 75 mg kg-1 for Mehlich-3 P) (Gibson et al. 2000; Maryland Department of Agriculture 2005).

The lag time between BMP implemen-tation and water quality improvements can


Figure 8Mehlich-3 extractable soil phosphorus concentration of surface soil (0 to 5 cm depth) under a corn-soybean rotation as a function of basing poultry litter application on crop nitrogen needs, crop phosphorus needs, and soil test phosphorus, in the Coastal Plains of Maryland.

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320

often exceed the monitoring period due to limited long-term funding opportunities for this type of research (National Research Council 2001). Despite our knowledge of

controlling processes, it is difficult for the public to understand or accept this lack of response. When public funds are invested in remediate programs, rapid improvements

in water quality are usually expected. Thus, assessment of effectiveness of P-based nutri-ent management BMPs should consider the re-equilibration of watershed and lake eco-systems, where P sinks may become sources of P. It is also important in any watershed P loss reduction strategy to address mitigation of nonagricultural sources of P in order to bring about lasting improvements in water quality.

Summary and ConclusionsSummary. Phosphorus-based management on poultry farms embodies a complex array of interdependent factors, watershed pro-cesses, and economic pressures external to the farm. There are many measures and practices that can be used to manage nutrients in rain-fed and irrigated farming systems. Many of these have been assigned codes and standards developed by NRCS to ensure their appro-priate implementation and maintenance (table 1). It must not be forgotten, however, that there is an increasing financial and legal liability being imposed on farmers to man-age their on-farm fertilizer resource, poultry litter and manure in a sustainable manner.

Sustainable P management begins with sound feed decisions, which in the poultry industry lies with the integrator rather than the individual farmer. Phosphorus inputs onto a farm should be matched as closely as possible with P export as poultry or crop products. The short-term impacts of land-applying poultry manure or litter on P loss can be successfully mitigated with many of the nutrient management measures discussed (table 3). Long-term solutions are likely to include development of alternative uses for manure and litter. However, it is clear that P management at both farm and watershed scales involves a complex suite of various options, which must be customized to meet site-specific needs.

Even though there has been a concerted effort to implement remedial measures through voluntary and regulatory means, the long-term challenges of accumulating manure and litter on poultry farms has been and remains difficult to overcome. Research that better quantifies the sinks and sources of P as it is transported through a watershed will help develop realistic expectations for BMPs. However, more research is not the single or final solution. Many farmers simply do not have the financial resources to imple-ment and maintain costly remedial measures.

401

Table 4Runoff, phosphorus loss, and crop yield as a function of basing poultry litter applications on a crop nitrogen requirement (N-based), crop phosphorus requirement (P-based), and soil test phosphorus as Mehlich-3 P (STP) for 0.1 ha plots in Coastal Plains region of Maryland.

Parameter Treatment* 2000 2001 2002 2003 2004

Rainfall (cm) 7.7 37.1 32.2 64.3 108.3Runoff (cm) 0.05 1.25 4.00 4.50 8.00

Runoff phosphorus loss (g ha–1)Dissolved P N-based 0.33 29 466 2,050 3,112 P-based 0.05 34 72 268 1,063 Soil test P 0.07 19 52 144 517 Decrease† 79% 34% 89% 93% 83%Total P N-based 2.37 185 2,067 2,509 3,493 P-based 1.08 170 1,361 1,633 1,386 Soil test P 1.35 124 1,016 1,300 689 Decrease† 43% 33% 51% 48% 80%

Crop yield (bushels ac–1)Corn N-based 205 120 32 110 142 P-based 192 113 51 94 151 Soil test P 181 118 40 100 134Soybeans N-based 55 43 27 42 46 P-based 52 42 29 40 48 Soil test P 50 42 27 40 45* Amounts of P applied in poultry litter averaged 75, 35, and 0 kg P ha–1 for N-based, P-based, and soil test P treatments, respectively.† Percent decrease in runoff P loss from soil test P compared to N-based litter treatment.


Despite there being a variety of programs to help defray remedial costs, institutional red-tape and conflicting requirements often limit program enrollment and hinder wide-spread adoption.

Whatever position one takes, recent lawsuits across the United States, question-ing the sustainability of P management on poultry farms have brought adoption of responsible land stewardship to the forefront of research, extension, and policy-making communities. By stepping up to provide sound science to support BMPs, research-ers can provide an invaluable service to the farming community. By demonstrating good science, extension can gain the confidence of the farming community. By adopting good science and practices, policy makers can actually implement recommendations and legislation that is achievable.

Conclusions. Clearly, there are many challenges facing poultry production to be overcome. These involve the overall sustainability of poultry operations, finding alternative uses for manure and litter, mov-ing manure and litter to areas of feed and forage production, and adoption and main-tenance of innovative BMPs at farm and watershed scales.

In terms of operation sustainability and environmental stewardship, is there a site-specific carrying capacity of the land that is appropriate for such intensive agricultural production? At some stage, the capacity of watersheds to assimilate nutrients, assum-ing some transport of manure from P-rich to P-deficient areas, should be determined and used in strategic planning of future development, expansion, or realignment of poultry operations.

Can more alternative uses for manure and litter be developed? As manure becomes competitive with mineral fertilizer in terms of nutrient value, it is likely alternative uses will be developed. For instance, advanced composting that could include bird mortality, when biosecurity is not an issue, pelletizing and granulation to produce a more valuable product with more use options, and use as a bioenergy source. It is expected that in the near future all these options, particularly bioenergy, will become increasingly viable economically.

Can the transport of manure within and among watersheds be encouraged to fully utilize this valuable P resource? The wider adoption of manure hauling that links

producers with buyers will greatly enhance the sustainability of poultry operations over a larger geographic area. The success of non-profit programs supported by water-shed agricultural councils, industry, and state agencies, such as that in the Eucha-Spavinaw and Illinois River watersheds, will provide a valuable demonstration model for other watersheds.

Can poultry production be environmen-tally sustainable? As with all confined animal feeding operations, sustainability of poultry operations hinges on reducing the P imbal-ance at farm and watershed scales through carefully managed feeding strategies. For example, the water solubility of P in poultry manure and litter is a highly variable prop-erty that has been directly linked to P runoff potential. However, are there some additional dietary options that could be managed or tai-lored to reduce P solubility?

Can cost and P-loss reduction efficien-cies of existing BMPs be enhanced further? Appropriate land management and BMP tar-geting will always be needed to minimize the risk of land applied P entering water ways. Overall, this involves identifying and avoid-ing critical source area applications, use of buffers or riparian zones, grazing manage-ment, stream bank exclusion (e.g., CREP involvement), and subsurface injection with innovative applicators where possible.

However, the bottom line is still who will pay to adopt costly new strategies? Should it be the public who want cheap produce and clean water? Should it be the integra-tors who are meeting a market demand and profitability margins? Or should it be the producers who are managing manure and lit-ter? The answer is all of the above. The crucial question is how can the financial respon-sibility fairly be apportioned among those directly involved in poultry operation and those benefiting from them.

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