C. Wesley Wood

Role of aquaculture pond sediments in sequestration of annual global carbon emissions

Aquaculture ponds sequester about 16.6MTyr(-1) of organic carbon worldwide representing around 0.21% of annual, global carbon emissions.

Ammonia emissions from field-simulated cattle defecation and urination.

Atmospheric ammonia (NH(3)) is a concern because of its environmental impact. The greatest contribution to atmospheric NH(3) comes from agricultural sources. This study quantified NH(3) volatilization from cattle defecation and urination on pasture under field conditions in Auburn, Alabama. Treatments consisted of beef feces, dairy feces, dairy urine, and a control. The experiment was conducted during four seasons from June 2003 to April 2004. Fresh feces or urine was applied onto grass swards, and NH(3) volatilization was measured up to 14 d after application using an inverted chamber method. Dairy urine was the only significant source of NH(3). Ammonia nitrogen (N) loss differed among seasons, ranging from 1.8% in winter to 20.9% during the warmer summer months. Cumulative volatilization was best described in this experiment by the equation % NH(3)-N loss = N(max) (1 - e(-ct))(i). The highest rate of NH(3) volatilization generally occurred within 24 h. This study suggests that NH(3) volatilization from cattle urine on pasture is significant and varies with season, whereas NH(3) volatilization from cattle feces is negligible.

Nitrogen budget for fescue pastures fertilized with broiler litter in major land resource areas of the southeastern US

The southeast US produces a tremendous number of broiler chickens (Gallus gallus), which in turn produce massive quantities of litter (manure and bedding materials). In the Southeast, litter is most often disposed of via land application to pastures, however, the ultimate fate of much of the applied nitrogen (N) is not known. We have constructed N budgets for three sites across the southeastern U.S. in an effort to determine how much of the applied N is useful for plant production and how much is left to be absorbed by the environment. Study sites were located in the Coastal Plain (Alabama), Piedmont (Georgia), and Cumberland Plateau (Tennessee) Major Land Resource Areas (MLRA) of the southeastern US. Litter was applied in the Spring of two consecutive years at a rate to supply 70 kg of available N ha−1. The total amount of N applied ranged from 103 to 252 kg N ha−1 depending on site and year. Nitrogen fluxes monitored in this study were broiler litter N, ammonia (NH3) volatilization, denitrification, plant uptake, and leaching. Plant uptake represented the largest flux of applied N, averaging 43% of applied N. Losses due to NH3 volatilization and denitrification combined were only 6% of applied N on average. Loss of N due to NO3-N leaching appeared to be significant only at the Coastal Plain site where NO3-N concentrations in the groundwater peaked at 38 mg N l−1. We believe the majority of excess N shown in these budgets is likely accounted for by leaching losses and soil accumulation. Regardless of these assumptions and low gaseous losses, it is apparent that on average, 57% of applied N is destined for a fate other than plant uptake. The results of this study indicate that land-application of broiler litter at currently recommended rates has the potential for negative impacts on the environment of the southeastern U.S. in the long-term.

Nutrient Loss in Leachate and Surface Runoff from Surface-Broadcast and Subsurface-Banded Broiler Litter

Subsurface band application of poultry litter has been shown to reduce the transport of nutrients from fields in surface runoff compared with conventional surface broadcast application. Little research has been conducted to determine the effects of surface broadcast application and subsurface banding of litter on nutrients in leachate. Therefore, a field experiment was conducted to determine the effects of subsurface band application and surface broadcast application of poultry litter on nutrient losses in leachate. Zero-tension pan and passive capillary fiberglass wick lysimeters were installed in situ 50 cm beneath the soil surface of an established tall fescue ( Schreb.) pasture on a sandy loam soil. The treatments were surface broadcast and subsurface-banded poultry litter at 5 Mg ha and an unfertilized control. Results of the rainfall simulations showed that the concentrations of PO-P and total phosphorus (TP) in leachate were reduced by 96 and 37%, respectively, in subsurface-banded litter treatment compared with the surface-applied litter treatment. There was no significant difference in PO-P concentration between control and subsurface-banded litter treatment in leachate. The trend in the loading of nutrients in leachate was similar to the trend in concentration. Concentration and loading of the nutrients (TP, PO-P, NH-N, and NO-N) in runoff from the subsurface-banded treatment were significantly less than for the surface-applied treatment and were similar to those from control plots. These results show that, compared with conventional surface broadcast application of litter, subsurface band application of litter can greatly reduce loss of P in surface runoff and leachate.

Population dynamics and genetic variability of Escherichia coli in a mixed land-use watershed

Better understanding of Escherichia coli population dynamics and genetic variability in the secondary habitat is essential to improve fecal contamination monitoring and contamination pathway characterization. In this study, water samples were collected monthly over a one-year period at eight locations in the Catoma Creek watershed, a mixed land-use watershed in Central Alabama. E. coli concentrations varied from 17 to 12,650 CFU/100 ml and were well correlated with stream flow rates. Repetitive sequence-based PCR DNA fingerprinting was used to generate 271 unique DNA fingerprint patterns from 502 E. coli isolated from water samples. Cluster analysis showed an overall similarity of 32.8% across all DNA fingerprints. Multivariate analysis of variance (MANOVA) showed that E. coli genotypes had a tendency to cluster according to season and stream flow rather than sampling sites. MANOVA of a subset of data within a given season and flow rate, however, revealed some geographical differentiation between urban and rural sampling sites. The results indicate that genetic diversity of E. coli populations was not only high in the secondary habitat but also varied with season, flow conditions and, to a lesser extent, sampling location. To our knowledge, this is the first report relating E. coli genotype to stream flow.

Differentiation of Life-History Traits among Palmer Amaranth Populations (Amaranthus palmeri) and Its Relation to Cropping Systems and Glyphosate Sensitivity

Palmer amaranths ability to evolve resistance to different herbicides has been studied extensively, but there is little information about how this weed species might be evolving other life-history traits that could potentially make it more aggressive and difficult to control. We characterized growth and morphological variation among 10 Palmer amaranth populations collected in Florida and Georgia from fields with different cropping histories, ranging from continuous short-statured crops (vegetables and peanut) to tall crops (corn and cotton) and from intensive herbicide use history to organic production. Palmer amaranth populations differed in multiple traits such as fresh and dry weight, days to flowering, plant height, and leaf and canopy shape. Differences between populations for these traits ranged from 36% up to 87%. Although glyphosate-resistant (GR) populations collected from cropping systems including GR crops exhibited higher values of the aforementioned variables than glyphosate-susceptible (GS) populations, variation in traits was not explained by glyphosate resistance or distance between populations. Cropping system components such as crop rotation and crop canopy structure better explained the differences among populations. The higher growth of GR populations compared with GS populations was likely the result of multiple selection forces present in the cropping systems in which they grow rather than a pleiotropic effect of the glyphosate resistance trait. Results suggest that Palmer amaranth can evolve life-history traits increasing its growth and reproduction potential in cropping systems, which explains its rapid spread throughout the United States. Furthermore, our findings highlight the need to consider the evolutionary consequences of crop rotation structure and the use of more competitive crops, which might promote the selection of more aggressive biotypes in weed species with high genetic variability. Nomenclature: glyphosate; Palmer amaranth, Amaranthus palmeri S. Wats.; corn, Zea mays L.; cotton, Gossypium hirsutum L.; peanut, Arachis hypogaea L.

Evaluation of Nitrogen Bioavailability Predictors for Poultry Wastes

Long-term land application of manure, litter, and dead-bird compost generated during poultry (Gallus, gallus) production may oversupply nitrogen (N) and result in nitrate (NO3-N) contamination of groundwater. A barrier to judi- cious use of poultry waste as a fertilizer is the absence of management tools for prediction of waste-derived N released during the plant growing season. This study was conducted to establish an N extraction method for poultry wastes as a predictor of soil N release owing to land application of poultry waste. We correlated N released from 87 different poultry wastes in a 60-day incubation with seven bioavailability predictors. Bioavailability predictors included autoclave-calcium chloride (CaCl2) extraction, bicarbonate extraction, Walkley-Black (acid dichromate) digestion, acid permanganate diges- tion, pepsin digestion, protein extraction, and barium hydroxide extractable glucose. Results indicate that acid permanga- nate digestion (r=0.77) has the highest potential for predicting N mineralized from poultry wastes followed by sodium bi- carbonate extraction (r=0.51). However, the relationships are not strong enough to indicate that these methods would be useful in a practical, predictive sense.

Effect of Fish Pond Effluents Irrigation on French Beans in Central Kenya

Abstract When fish are recovered from ponds, the effluent is often drained presenting both an environmental challenge and an agricultural opportunity. The effects of irrigation with pond effluent and its interaction with applied fertilizer were assessed in a field experiment using French bean (Phaseoulus vulgaris) over two growing seasons near Sagana, Kenya. Fresh yield of beans was recorded at harvest, and leaf samples were collected for determination of tissue nutrient concentration. In the first season plots receiving canal water and fertilizer at recommended rates had the highest yield (9.1 Mg fresh pod ha−1), while those receiving no fertilizer or irrigation had the least yield (1.3 Mg fresh pod ha−1). In the second season, the highest (4.4 Mg ha−1) fresh pod yield was observed in pond effluent irrigated and fertilized plots, while the lowest (1.3 Mg ha−1) was observed in nonirrigated/unfertilized plots. Low nutrient status in the pond water was responsible for low yield where it was substituted for canal water. Pond water from the Sagana Fish Farm supplied low amounts of nitrogen (N) and phosphorus (P) for crops, indicating that recommended rates of mineral fertilizers should be used when pond water is used for irrigation.

Nitrogen, phosphorus, and potassium effects on biomass yield and flavonoid content of American skullcap (Scutellaria lateriflora)

ABSTRACT Greenhouse experiments were conducted to determine the effects of nitrogen (N), phosphorus (P), and potassium (K) fertilizer on biomass yield and flavonoid content of American skullcap (Scutellaria lateriflora). Each experiment was carried out two times and consisted of six levels of each nutrient. The regressions gave maxima for dry matter, baicalein yield, and chrysin yield at 446, 412, and 351 kg N/ha for N fertilizer, respectively. Dry matter yield exhibited linear response to P application. The yield of scutellarein, baicalin, baicalein, and chrysin increased with addition of P. The regression gave maximum for dry matter at 208 kg K/ha for K fertilizer. A linear response to K fertilization was observed for scutellarein concentration. P application had the greatest effect on the flavonoids analyzed, whereas K had least, which may be attributed in part to the presence of K in the fritted clay medium.

Harvesting Number and Timing Effects on Shoot Yield and Flavonoid Content in Organically Grown American Skullcap (Scutellaria lateriflora)

A field experiment was conducted in Alabama to determine the effect of timing and frequency of harvest on shoot yield and flavonoid content of American skullcap. In the first year (2008), harvesting twice gave 36% higher yield than harvesting once. In the second year (2009), plant die-off late in the season prevented a comparison of two and three harvests, so only the effects of early and late harvest were compared. There was no difference in yield between early or late harvesting. Plant height and density, percent dry matter, and shoot yield were higher in the first harvest than the second harvest. In 2008, the yield and concentration of flavonoid baicalein was the highest. In 2009, the yield and concentration of baicalin was the highest, followed by baicalein and apigenin. There were no differences in flavonoid yield between early and late harvest. Flavonoid yield in 2009 was 58% higher in the first harvest than in the second.