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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2009.02.003 Byline: Michael B. Jenkins (a), Dinku M. Endale (a), Harry H. Schomberg (a), Peter G. Hartel (b), Miguel L. Cabrera (b) Abbreviations: NT, no-till; CT, conventional-till; PL, poultry litter; CF, conventional fertilizer Abstract: Thirteen metric tons of poultry litter are produced annually by poultry producers in the U.S. Poultry litter contains the sex hormones estradiol and testosterone, endocrine disruptors that have been detected in surface waters. The objective of this study was to evaluate the potential impact of poultry litter applications on estradiol and testosterone concentrations in subsurface drainage and surface runoff in irrigated crop land under no-till and conventional-till management. We conducted an irrigation study in fall of 2001 and spring of 2002. Four treatments, no-till plus poultry litter, conventional-till plus poultry litter, no-till plus conventional fertilizer, and conventional-till plus conventional fertilizer, were evaluated. Flow-weighted concentration and load ha.sup.-1 of the two hormones were measured in drainage and runoff. Soil concentrations of estradiol and testosterone were measured. Based on comparisons to the conventional fertilizer (and control) treatments, poultry litter did not add to the flow-weighted concentration or load ha.sup.-1 of either estradiol or testosterone in subsurface drainage or surface runoff. Significant differences were, however, observed between tillage treatments: flow-weighted concentrations of estradiol were greater for no-till than conventional-till plots of the June irrigation; and runoff loads of both estradiol and testosterone were less from no-till than conventional-till plots for the November irrigation. Although the differences between no-till and conventional-tillage appeared to affect the hydrologic transport of both hormones, the differences appeared to have inconsequential environmental impact. Author Affiliation: (a) Southern Piedmont Conservation Research Unit, USDA-ARS, J. Phil Campbell, Sr., Natural Resource Conservation Center, 1420 Experiment Station Road, Watkinsville, GA 30677, USA (b) University of Georgia, Athens, GA 30605, USA Article History: Received 19 June 2008; Revised 8 January 2009; Accepted 8 February 2009

A major concern of the broiler industry is the volatilization of ammonia (NH3) from the mixture of bedding material and broiler excretion that covers the floor of broiler houses. Gypsum has been proposed as a litter amendment to reduce NH3 volatilization, but reports of NH3 abatement vary among studies and the mechanism responsible for decreasing NH3 volatilization is not well understood. The goal of this study was to evaluate the effect of adding 20 or 40% flue-gas desulfurization gypsum (FGDG) to broiler litter on pH, electrical conductivity (EC), water potential, urea-degrading bacteria abundance, NH3 and carbon dioxide (CO2) evolution, and nitrogen (N) mineralization in several 21-d experiments. The addition of FGDG to broiler litter increased EC by 24 to 33% (P < 0.0001), decreased urea-degrading bacteria by 48 to 57% (P = 0.0001) and increased N mineralization by 10 to 11% (P = 0.0001) as compared to litters not amended with FGDG. Furthermore, the addition of FGDG to broiler litter decreased NH3 volatilization by 18 to 28% (P < 0.0001), potentially resulting from the significantly lower litter pH values compared to un-amended litter (P < 0.0001). Findings of this study indicate that amending broiler litter with 20% FGDG can decrease NH3 volatilization and increase the fertlizer value of broiler litter. [ABSTRACT FROM AUTHOR]

Abstract: We studied the effect of five bedding materials (wood shavings, sawdust, peanut hulls, wheat straw and shredded paper) and PLT™ (a commercial formulation of Na bisulfate) in factorial combinations, on NH3 emissions from broiler manure. Treatments were incubated for 11 days at 25°C and 98% relative humidity. Ammonia was trapped in 0.1N H2SO4 and measured colorimetrically as , and CO2 was monitored with an infrared analyzer. Ammonia and CO2 emissions were suppressed by PLT™ throughout the study. Wheat straw, wood shavings, and sawdust, with C(total)/N(total)>50 or C(biodegradable)/N>20, had low NH3 emissions. Total NH3 emissions from peanut hulls and shredded paper were the highest, probably due to peanut hulls’ low C/N ratio and shredded paper’s alkaline pH. No significant interactions on NH3 emissions were detected between PLT™ and bedding materials. [Copyright &y& Elsevier]

A tool to estimate the amount of net N mineralized under field conditions would be useful to adjust N fertilizer rates. A simulation model of soil N may be useful to develop such estimates, but must first be evaluated under the conditions in which it will be used. In this work, we implemented the N subroutine of CERES-N in Stella 6.0 modeling software to simulate net N mineralized from soil organic matter and cotton residues at three locations in a Coastal Plain field of south Georgia. The model was first calibrated with laboratory data of net N mineralized from an incubation study of cotton leaves and stems, and then used to simulate net N mineralized at three field locations. The calibrated model underestimated net N mineralized at two of the field locations by 45% and 56%, respectively. This underestimation was apparently caused by an underestimation of N mineralized from soil organic matter. To explore possible reasons for the underestimation, we collected soil samples monthly for 1 year to measure potentially mineralizable N at the three field locations, and used the data to modify the rate of soil organic matter mineralization throughout the year according to a sinusoidal wave. Simulated values of net N mineralized with this modification were within the 95% confidence interval for field-measured values. These results suggest that further research should be conducted to study the dynamics of the microbial population and microfauna present in soil, which may be partially responsible for seasonal changes in N mineralization rates. [Copyright &y& Elsevier]

Nitrogen (N) mineralization rates in forest systems typically decrease with decreasing temperature. Temperature decreases with increasing elevation. Thus, N mineralization rates are expected to decrease with increasing elevation. However, soil N mineralization rates at the Coweeta Hydrologic Laboratory, NC, USA are higher at the highest elevation. Causes of higher mineralization rates at the higher elevation have yet to be explained. Alternative hypotheses to explain patterns of mineralization rates along this elevation gradient include (1) a mineralization promoter in decomposing herbs, leaf litter, or soil of the high elevation, (2) low pH in the low elevation soils which inhibit mineralization, (3) greater total N pools at the high elevation, (4) low moisture availability in low elevation soils, (5) differences in soil texture, and (6) differences in biological communities. Previous studies did not support our N mineralization promoter hypothesis, nor does soil pH explain mineralization rates. In this study we constructed N budgets for a high elevation northern hardwood and a low elevation oak-pine site to determine if differences in N pools and fluxes are sufficient to explain differences in N mineralization rates. Evaluating N in the upper 0–10 cm of mineral soil, forest floor, overstory biomass, annual canopy litter fall, understory herb turnover, rainfall, canopy throughfall, and in soil solution, we found that the high elevation stand has more stored N and greater N fluxes than does the low elevation stand. The high elevation stand has many characteristics of a stand in an early stage of N saturation, while the low elevation stand characterizes an N-limited forest. Causes of greater N storages and fluxes at the high elevation northern hardwood site are not obvious. [Copyright &y& Elsevier]

Cotton has become a dominant crop in the southeastern USA, but only about 12% of the 620,000 ha of cotton (Gossipium hirsutum L.) in Georgia, for example, is under conservation tillage. Georgia and bordering states produce about 42% of the poultry in the United States and in Georgia alone, this results in over 1.6 million Mg of poultry litter (PL) annually. The fertilizer value of PL is well-recognized but much of it is applied to pastures and only a small percentage is applied to crop land. Limited information is available on the response of cotton to PL as fertilizer in conservation tillage systems in the Southeast. The performance of cotton under two tillage and two fertilizer treatments was evaluated from 1996 to 1999 to highlight management options for increased adoption of conservation tillage and PL use. Cotton, followed by a rye (Secale cereale L.) cover crop, was grown under a factorial arrangement of tillage (no-till (NT) vs conventional tillage (CT)) and fertilizer (ammonium nitrate, as conventional fertilizer (CF) vs PL) on a Cecil sandy loam (clayey, kaolinitic thermic Typic Kanhapludult; Chromi-Alumic Acrisol) near Watkinsville, Georgia. Average lint yield from 1996 to 1999 was in the sequence no-till poultry litter (NTPL)>no-till conventional fertilizer (NTCF)>conventional tillage poultry litter (CTPL)>conventional tillage and fertilizer (CTCF). Differences were significant at P≤0.05 for NTPL vs CTPL, NTPL vs CTCF, and NTCF vs CTCF. Average yield differences were also significant between NT and CT but not PL and CF. PL yielded more than CF only in 1997. NT generally had a more favorable soil water regime than CT. Yield differences among treatments occurred during the first 3 years only. Drought in the fourth year reduced yield across all treatments and negated treatment effects. Lint yield would increase in the southeastern USA and an additional outlet for the PL would be created by adopting NT and fertilizing with PL in cotton production. [Copyright &y& Elsevier]

To increase microalgae biomass production and support high density cultures in photobioreactors artificial illumination systems have been designed to increase photosynthetic activity. Supplemental lighting systems are commonly composed by a combination of chlorophyll ( a + b ) strongly absorbed wavelengths, while weakly absorbed wavelengths are not present. At this work we compared the photosynthetic activity and biomass production induced by chlorophyll ( a + b ) strongly versus weakly absorbed wavelengths in Scenedesmus bijuga microalgae cultures at different biomass densities. Photosynthetic activity and biomass production induced by 4 different wavelengths using LEDs (blue – peak at λ470 nm; green – peak at λ530 nm; red – peak at λ655 nm; and white-4100 K) were measured and analyzed on high-density cultures of S. bijuga . As culture density increased the chlorophyll ( a + b ) weakly absorbed green light penetrated deeper into the samples inducing higher oxygen evolution at culture concentration of 1.45 g L −1 compared to the chlorophyll ( a + b ) strongly absorbed red light. High-density culture (2.19 g L −1 ) cultivated under green light showed higher biomass production rate (30 mg L −1 d −1 ) with a 8.43% biomass growth in a 6-day period compared to the same quantum flux of red light that induced 4.35% biomass growth on the same period. The integration of green LEDs into photobioreactors lighting apparatus could improve the existing systems composed predominantly by red and blue LEDs increasing biomass productivity of high-density cultures at latter stages of microalgae cultivation. [ABSTRACT FROM AUTHOR]

While several studies have documented the effect of no-till (NT) and conventional-till (CT) practices on soil organic matter and nutrients, very limited information is available on the effect of tillage practices on amino acids in soil. This study was conducted to measure the concentrations of bound amino acids in humic (HA) and fulvic acids (FA) in samples collected from soils under NT and CT management. Samples were obtained from two long-term studies at the Horseshoe Bend Experimental Area and at the Bledsoe Research Farm in Georgia, USA. The total amount of bound amino acids in HA was higher in NT than in CT samples. In contrast, the concentration of bound amino acids in FA was higher in CT than in NT samples. Neutral amino acids dominated in all samples of HA and FA. Acidic amino acids had the lowest concentrations. In all samples of HA and FA, the dominant amino acids were: glutamic acid, alanine, glycine and valine. β-alanine and lysine concentrations in HA and FA were higher in NT than in CT, indicating a higher microbial biomass in NT soils. Proline concentrations in FA were higher in CT than in NT samples. Electron paramagnetic resonance (EPR) was applied to characterize HA and FA extracted from soils under NT and CT. The level of native radicals for each sample of HA and FA was estimated. Strong effects of gaseous ammonia on spin concentration enhancement and also higher values of g-value were found to be associated with the formed “transient” radicals. HA from NT management was characterized by higher molecular weight and a higher degree of condensation of aromatic constituents than HA from CT. [Copyright &y& Elsevier]

Soil microorganisms play a critical role in cover crop (CC) residue decomposition and nutrient cycling in agroecosystems. However, the impact of CC residue management and dry-wet cycles on soil and residue microbiota and their potential ecosystem functions is largely unknown. To fill these knowledge gaps, an incubation experiment was conducted with two CC residues, crimson clover (Trifolium incarnatum L.) and cereal rye (Secale cereale L.), and two residue placements (incorporated vs surface-applied). Each CCs by placement treatment was subjected to four dry-wet cycles (20-d each) for a total of 80-d. Crimson clover residues had higher water storage capacities than cereal rye, and the rate at which water was lost from surface-applied CC residues increased after each successive wetting event. Rapid drying of surface-applied CC residues quickly suppressed CO 2 fluxes, which increased immediately upon rewetting. Incorporated CC residues maintained water content for longer duration than surface-applied residues and showed greater colonization by soil prokaryotes and saprophytic fungi. Thus, significantly more C and N were mobilized from incorporated residues by 80-d than from surface-applied residues (p < 0.05). Due to differences in residue chemistry, CC residue types have a stronger impact on soil N levels than residue placement. Thus, residue chemistry strongly influenced soil prokaryotic and fungal diversity, community structure, and functionality. While crimson clover-amended soils (N-rich environments) were dominated by copiotrophs, oligotrophs dominated cereal rye-amended soils (N-poor soil environments). On the other hand, residue placement may have a greater effect than residue type in determining residue microbiota, particularly prokaryotes. Based on these findings, we can conclude that the effect of residue placement on C and N mineralization during repeated dry-wet cycles is primarily explained by differences in water dynamics between incorporated and surface-applied CC residues. • Cover crop residue type, residue placement, and dry-wet cycles strongly influenced microbial processes and functions. • Incorporated residues mineralized more C and N than surface-applied residues. • C mineralization from surface-applied residues quickly dropped following rewetting due to rapid loss of water. • Residue type influenced soil prokaryotic and fungal diversity, community structure, and functionality. • When incorporated, residues are more colonized by soil prokaryotes and saprophytic fungi. [ABSTRACT FROM AUTHOR]