| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
USDA-ARS, J. Phil Campbell Sr. Natural Resource Conservation Center, 1420 Experiment Station Road, Watkinsville, GA 30677-2373
* Corresponding author (afranz{at}uga.edu).
Received for publication May 19, 2003.
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONSREFERENCES |
|---|
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONSREFERENCES |
|---|
One concern with repeated animal manure application is the accumulation of trace elements that might become toxic to plants, animals, and humans (Pierzynski et al., 2000). Repeated application of broiler litter with significant concentrations of trace elements may therefore pose an environmental threat with time, although sufficient long-term evaluations under various management conditions are currently not available. Kingery et al. (1994) observed more than threefold increases in surface-soil (0–15 cm) concentrations of Cu and Zn following 21 ± 4 yr of heavy application of poultry litter (1.1 ± 0.5 kg m–2 yr–1) to variably managed tall fescue (Festuca arundinacea Schreb.) stands. This study was from a survey of 12 sites managed in a variety of manners without experimental control.
Various elements are added to poultry rations, such as As, Co, Cu, Fe, Mn, Se, and Zn (Moore, 1998). Copper sulfate is often added to the diet of broilers to increase weight gain and avoid diseases (Johnson et al., 1985). Other elements are added to feed so that young birds can tolerate various stresses under high-population conditions in the house (Tufft and Nockels, 1991). It is generally assumed that concentrations of these elements applied to soil do not reach toxic levels, although various trace elements have been detected in surface runoff from pastures fertilized with broiler litter (Moore, 1998). Accumulation of Cu in soil may have adverse effects on plant growth, as well as the activity of aquatic organisms should excessive runoff occur following broiler litter application (Pierzynski et al., 2000). Detectable levels of As were found in cattle hair samples when cattle grazed pastures fertilized with broiler litter, suggesting potential animal health impacts (Isaac et al., 1978).
Although the quantity of trace elements supplied with broiler litter may not be high enough to cause acute toxicity in plants, animals, or humans (Moore et al., 1995), there is growing concern for the possibility of subclinical effects due to long-term exposure to slightly elevated quantities of various trace elements (Pierzynski et al., 2000). Long-term grazing management studies are needed to document the levels of various trace elements that might accumulate in soil, which could ultimately affect soil microorganisms, plants, animals, and humans through various interactions in the food chain (McLaughlin et al., 1999). The Environmental Protection Division of the Georgia Department of Natural Resources has established critical soil concentrations of various trace elements that would trigger notification requirements (Environmental Protection Division, 1994).
Grazing of a forage crop compared with haying returns much of the manure directly to the land, which should affect trace element distribution in soil (Follett and Wilkinson, 1995). To better understand trace element cycling in forage management systems receiving broiler litter, comparisons are needed along a gradient in forage utilization from unharvested (no utilization) to grazing (forage consumption with excreta returned to soil) to hay harvest (full utilization with aboveground forage removed). Harvest management would be expected to alter the distribution of trace elements among soil depths, because of the effects of animal traffic, ruminant processing of forage (i.e., biological transformation of nutrients), and nutrient removal with hay.
The extent of trace element accumulation within the immediate surface soil layers under repeated broiler litter application has not been adequately investigated. Our objective was to characterize the concentration and depth distribution of various trace elements in response to broiler litter fertilization under different forage utilization strategies. We hypothesized that with equivalent amounts of total N applied, fertilization with broiler litter versus inorganic or a combination of inorganic plus biological N fixation would affect the quantity and depth distribution of trace elements in soil.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONSREFERENCES |
|---|
Experimental Design
The experimental design (3 x 4 factorial arrangement) was a split-plot with three replications. Individual paddocks were 0.69 ± 0.03 ha. Spatial design of paddocks minimized runoff contamination and handling of animals through a central roadway. Each paddock contained a 3- x 4-m shade, mineral feeder, and water trough placed in a line 15 m long near the top of the landscape. Unharvested and hayed exclosures within a paddock were 100 m2. Whole plots were fertilization strategy (n = 3) and split-plots were harvest strategy (i.e., forage utilization) (n = 4) for a total of 36 experimental units.
Fertilization was targeted to supply 20 g total N m–2 yr–1 using one of the following strategies: (i) inorganic fertilizer as NH4NO3 broadcast in split applications in May and July, (ii) inorganic fertilizer with half of the N as NH4NO3 broadcast in July and the other half assumed fixed and released by crimson clover (Trifolium incarnatium L.) cover crop during the previous winter and spring, and (iii) by broiler litter broadcast in split applications in May and July (Table 1). Broiler litter was supplied by the same chicken producer, who spread the manure with wood-shaving bedding (houses cleaned every 8 wk) with a commercial truck. We assumed that crimson clover would provide the equivalence of 11 g N m–2 yr–1 based on the results of a 3-yr study at a nearby site, where equivalent ‘Coastal’ bermudagrass hay yield (1.3 kg m–2 yr–1) was obtained with half the inorganic N when overseeded with crimson clover as with bermudagrass alone supplied with 22 g total N m–2 yr–1 (Carreker et al., 1977). Phosphorus and K applications varied among treatments, because excess P and K were applied with broiler litter to meet N requirements, while triple super phosphate and muriate of potash were applied based on soil testing recommendations with inorganic only and clover + inorganic fertilization. Dolomitic limestone (224 g m–2 event–1) was applied based on soil testing to inorganic only and clover + inorganic treatments in February 1995 and only to the inorganic treatment in November 1996. Crimson clover was direct-drilled in clover treatments at approximately 1 g m–2 in October each year. All paddocks were mowed in late April following soil sampling and residue was allowed to decompose [i.e., clover biomass in the clover + inorganic treatment and winter annual weeds (primarily Lolium annuum L. and Bromus catharticus Vahl.) in the other treatments].
|
Sampling and Analyses
Broiler litter was sampled by compositing approximately 1 kg of material from three to four different areas of each truckload just before application to the pasture. Three or four samples of litter (one from each truckload) per application period were digested (1 g of litter in a mixture of 10 mL concentrated nitric acid + 5 mL concentrated perchloric acid) with heating on a hot plate (for 5 min beyond the time when white, dense perchloric acid fumes appeared). The cooled digest was diluted with 10 mL of 25% HCl and brought to 100 mL volume with deionized water and subsequently analyzed for total element concentrations with inductively coupled plasma spectroscopy by the University of Georgia Agricultural and Environmental Services Laboratory (2003).
Soil was sampled in February 1999 at the end of 5 yr of management from a composite of eight 4.1-cm-diameter soil cores collected at depths of 0 to 3 and 3 to 6 cm. Surface residue from randomly selected areas (0.04 m2 each) within each of three zones within paddocks (i.e., 0- to 30-, 30- to 70-, and 70- to 120-m distances from shades) and within each exclosure was removed before soil coring. Soil was oven-dried (55°C, 72 h) and gently crushed to pass a 4.75-mm screen. The three subsamples within a paddock were composited before laboratory analyses.
Soil bulk density was calculated from the oven-dried soil weight and coring device volume and was reported along with soil organic C in Franzluebbers et al. (2001). Trace elements in soil were analyzed with inductively coupled plasma spectroscopy following the same digestion procedure previously described for broiler litter by the University of Georgia Agricultural and Environmental Services Laboratory. The effects of management on soil organic C and bulk density (Franzluebbers et al., 2001), particulate and biologically active soil C (Franzluebbers and Stuedemann, 2003), soil N (Franzluebbers and Stuedemann, 2001), soil P (Franzluebbers et al., 2002), and soil pH and nutrient cations (A.J. Franzluebbers, unpublished data, 2003) during this same evaluation period were reported elsewhere.
Trace element concentrations for the 0- to 6-cm depth were weighted based on bulk density differences among soil depth increments. Analysis of variance was conducted for each depth separately according to the split-plot design with three replications using SAS (SAS Institute, 1990). Effects were considered significant at p 
0.05. The fertilizer comparison was between broiler litter and the average of inorganic only and clover + inorganic regimes. In a preliminary analysis, there were few differences in soil trace element concentrations between inorganic only and clover + inorganic fertilization regimes. Correlations among soil variables at a depth of 0 to 6 cm were evaluated from a total of 36 observations.
|
RESULTS AND DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONSREFERENCES |
|---|
|
Forage utilization led to significant differences in Cu concentration at a depth of 0 to 3 cm (Table 2). Soil under grazed treatments had higher Cu concentration than under ungrazed treatments with broiler litter fertilization, but not with inorganic fertilization, although there was a similar tendency. At a depth of 0 to 3 cm, soil Cu concentration was 1.7 times greater under grazed than under ungrazed management with broiler litter and 1.3 times greater under grazed than under ungrazed management with inorganic fertilization. These changes in Cu concentration with respect to forage utilization coincided with similar changes in soil organic C concentration (Franzluebbers et al., 2001), although the association was rather weak (p = 0.07; Table 3). Apart from other trace element concentrations, soil microbial biomass C concentration was the most highly related property to soil Cu concentration (p = 0.004; Table 3), suggesting that Cu was associated with biological transformations of soil organic matter. Although extreme contamination of soil with various trace elements can inhibit soil microbial activity (Brookes, 1995), lower levels of trace element additions can stimulate microbial activity (Stuczynski et al., 2003). Soil Cu concentrations were within the range considered normal in soil (i.e., 2–60 mg kg–1; Bowie and Thornton, 1985), but greater than the levels of 1 to 4 mg kg–1 from Typic and Plinthic Kandiudults from the Coastal Plain region in Georgia (Gaskin et al., 2003).
|
Soil B and Mo concentrations were unaffected by the application of broiler litter compared with inorganic fertilization (data not shown). The quantity of B applied with broiler litter was minor (Table 1) and well below the natural variability that occurred among soil samples. Soil B (generally <0.6 mg kg–1, which was the analytical detection limit) and soil Mo (<0.5 mg kg–1, which was the analytical detection limit) concentrations were below the range considered normal for many soils (2–100 mg B kg–1 and 0.2–5 mg Mo kg–1; Brady, 1990). Even the minor amounts of these trace elements supplied with broiler litter would probably be beneficial to these eroded Ultisols.
Non-Essential Trace Elements
Soil Cd concentration was not affected by fertilization regime at either soil depth (Table 4). At both 0- to 3- and 3- to 6-cm depths, soil Cd concentration was greater under high grazing pressure than under unharvested and hayed management when averaged across fertilization regimes. There was also a tendency for Cd concentration to be higher under low grazing pressure than under ungrazed systems. Soil Cd concentration was highly related to particulate organic and microbial biomass C pools (p < 0.01; Table 3). These organic pools of C were higher with grazed than with ungrazed management (Franzluebbers and Stuedemann, 2003) and probably contributed to stronger sorption of Cd within various organic components during the cycling of Cd (Düring et al., 2002; Kaschl et al., 2002). The quantity of Cd supplied with broiler litter was minor (1.3 mg m–2 yr–1; Table 1) and about the same as what might have been applied with inorganic and clover + inorganic fertilization regimes (average of 1.5 mg m–2 yr–1) according to assumed Cd contaminant levels in P, K, and lime amendments (Pierzynski et al., 2000). Soil Cd concentrations were at the upper end of the range considered normal in soils (<1 to 2 mg kg–1; Bowie and Thornton, 1985; Holmgren et al., 1993), but these levels were not due to recent management inputs since values were high under all systems. On Typic and Plinthic Kandiudults from the Coastal Plain region in Georgia, soil Cd concentrations were <0.2 mg kg–1 and unaffected by long-term sewage sludge application (Gaskin et al., 2003).
|
Soil Ni concentration was unaffected by fertilization regime (Table 4). Nickel supplied with broiler litter was minor, but varied considerably from year to year (Table 1). Soil Ni concentration was unrelated to soil organic matter pools, but highly related to the concentration of soil Cr, Cu, Mn, Pb, and Zn (p < 0.01; Table 3), as well as to soil Al, K, and Na (data not shown). It appears likely that inherent soil characteristics, which were differentially exposed at the soil surface by previous land use and erosion, were responsible for variations in soil Ni and several other trace elements. Soil Ni concentrations were within the range considered normal (2–100 mg kg–1; Bowie and Thornton, 1985) and similar to levels (1–2 mg kg–1) for Typic and Plinthic Kandiulults from the Coastal Plain region in Georgia (Gaskin et al., 2003).
Soil Pb concentration was generally unaffected by fertilization regime, except for significantly higher soil Pb concentration with broiler litter than inorganic fertilization regimes under unharvested management at a depth of 3 to 6 cm (Table 4). It is unclear why this difference occurred at a depth of 3 to 6 cm and not at 0 to 3 cm. Forage utilization had no effect on soil Pb concentration. The quantity of Pb supplied with broiler litter was minor (10 mg m–2 yr–1; Table 1), but still larger than what might have been applied with inorganic and clover + inorganic fertilization regimes (average of 2.3 mg m–2 yr–1) according to assumed Pb contaminant levels in P, K, and lime amendments (Pierzynski et al., 2000). Soil Pb concentration was within the range considered normal (10–150 mg kg–1; Bowie and Thornton, 1985) and similar to those (5–22 mg kg–1) reported for a loamy sand in England (Keller et al., 2002).
|
CONCLUSIONS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONSREFERENCES |
|---|
0.01) and Cr and Zn (p 0.1), and negatively associated with concentration of B. It appears that the distribution of trace elements in soil was significantly modified by the dynamics of soil organic matter, which allowed greater sorption of many trace elements at the soil surface, especially with the generally greater application of trace elements with broiler litter fertilization. The risk of trace element contamination to receiving bodies of water following broiler litter application to grazed bermudagrass pastures might not be as great as perceived, despite elevated concentrations at the soil surface, because interactions of trace elements with high organic matter at the soil surface may limit transfer of these elements across the landscape. Further studies are needed to assess the bioavailability, in addition to total concentration, of both plant-essential and non-essential trace elements supplied to differently managed pastures with broiler litter application. |
ACKNOWLEDGMENTS |
|---|
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONSREFERENCES |
|---|
Related articles in JEQ:
This article has been cited by other articles:
|
|
 |
|
  J. A. Stuedemann and A. J. Franzluebbers Cattle performance and production when grazing Bermudagrass at two forage mass levels in the southern Piedmont J Anim Sci, May 1, 2007; 85(5): 1340 - 1350. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| The SCI Journals | Agronomy Journal | Crop Science | |||
| Vadose Zone Journal | Journal of Plant Registrations | ||||
| Journal of Natural Resources and Life Sciences Education |
Soil Science Society of America Journal |
