Sam Dennis

Down‐regulation of tissue N:P ratios in terrestrial plants by elevated CO2

Increasing atmospheric CO2 concentrations generally alter element stoichiometry in plants. However, a comprehensive evaluation of the elevated CO2 impact on plant nitrogen: phosphorus (N:P) ratios and the underlying mechanism has not been conducted. We synthesized the results from 112 previously published studies using meta-analysis to evaluate the effects of elevated CO2 on the N:P ratio of terrestrial plants and to explore the underlying mechanism based on plant growth and soil P dynamics. Our results show that terrestrial plants grown under elevated CO2 had lower N:P ratios in both above- and belowground biomass across different ecosystem types. The response ratio for plant N:P was negatively correlated with the response ratio for plant growth in croplands and grasslands, and showed a stronger relationship for P than for N. In addition, the CO2-induced down-regulation of plant N:P was accompanied by 19.3% and 4.2% increases in soil phosphatase activity and labile P, respectively, and a 10.1% decrease in total soil P. Our results show that down-regulation of plant N:P under elevated CO2 corresponds with accelerated soil P cycling. These findings should be useful for better understanding of terrestrial plant stoichiometry in response to elevated CO2 and of the underlying mechanisms affecting nutrient dynamics under climate change.

Review of Satellite Remote Sensing Use in Forest Health Studies~!2010-01-27~!2010-04-05~!2010-06-29~!

Satellite remote sensing has been used in forest health management as a method for vegetation mapping, fire fuel mapping, fire risk estimation, fire detection, post-fire severity mapping, insect infestation mapping, and relative water stress monitoring. This paper reviews the use of satellite remote sensing in forest health studies, including current research activities; the satellite sensors, methods, and parameters used; and their accuracy. The review concludes that the Moderate Resolution Imaging Spectroradiometer satellite data (MODIS) are more appropriate for most of the remote sensing applications for forest health than other current satellite data when considering temporal and spatial resolutions, cost, and bands. MODIS has a 1-2 day temporal and a 250-1000 m spatial resolution; the data are free and cover more spectral bands than other satellites (up to 36 bands). We recommend that physical and physiological modeling (e.g., evapotranspiration and biomass growth) be developed for remote sensing of forest health. Some additional satellite sensors, such as for high temperature estimates (as high as 1800 K) and sensors of narrow bands, are also needed.

Ascorbic acid, β-carotene, sugars, phenols, and heavy metals in sweet potatoes grown in soil fertilized with municipal sewage sludge

Municipal sewage sludge (MSS) used for land farming typically contains heavy metals that might impact crop quality and human health. A completely randomized experimental design with three treatments (six replicates each) was used to monitor the impact of mixing native soil with MSS or yard waste (YW) mixed with MSS (YW +MSS) on: i) sweet potato yield and quality; ii) concentration of seven heavy metals (Cd, Cr, Mo, Cu, Zn, Pb, and Ni) in sweet potato plant parts (edible roots, leaves, stem, and feeder roots); and iii) concentrations of ascorbic acid, total phenols, free sugars, and β-carotene in sweet potato edible roots at harvest. Soil samples were collected and analyzed for total and extractable metals using two extraction procedures, concentrated nitric acid (to extract total metals from soil) as well as CaCl2 solution (to extract soluble metals in soil that are available to plants), respectively. Elemental analyses were performed using inductively coupled plasma mass spectrometry (ICP-MS). Overall, plant available metals were greater in soils amended with MSS compared to control plots. Concentration of Pb was greater in YW than MSS amendments. Total concentrations of Pb, Ni, and Cr were greater in plants grown in MSS+YW treatments compared to control plants. MSS+YW treatments increased sweet potato yield, ascorbic acid, soluble sugars, and phenols in edible roots by 53, 28, 27, and 48%, respectively compared to plants grown in native soil. B-carotene concentration (157.5 μg g−1 fresh weight) was greater in the roots of plants grown in MSS compared to roots of plants grown in MSS+YW treatments (99.9 μg g−1 fresh weight). Concentration of heavy metals in MSS-amended soil and in sweet potato roots were below their respective permissible limits.

Corn Yield and Soil Nitrous Oxide Emission under Different Fertilizer and Soil Management: A Three-Year Field Experiment in Middle Tennessee.

Background A three-year field experiment was conducted to examine the responses of corn yield and soil nitrous oxide (N2O) emission to various management practices in middle Tennessee. Methodology/Principal Findings The management practices include no-tillage + regular applications of urea ammonium nitrate (NT-URAN); no-tillage + regular applications of URAN + denitrification inhibitor (NT-inhibitor); no-tillage + regular applications of URAN + biochar (NT-biochar); no-tillage + 20% applications of URAN + chicken litter (NT-litter), no-tillage + split applications of URAN (NT-split); and conventional tillage + regular applications of URAN as a control (CT-URAN). Fertilizer equivalent to 217 kg N ha-1 was applied to each of the experimental plots. Results showed that no-tillage (NT-URAN) significantly increased corn yield by 28% over the conventional tillage (CT-URAN) due to soil water conservation. The management practices significantly altered soil N2O emission, with the highest in the CT-URAN (0.48 mg N2O m-2 h-1) and the lowest in the NT-inhibitor (0.20 mg N2O m-2 h-1) and NT-biochar (0.16 mg N2O m-2 h-1) treatments. Significant exponential relationships between soil N2O emission and water filled pore space were revealed in all treatments. However, variations in soil N2O emission among the treatments were positively correlated with the moisture sensitivity of soil N2O emission that likely reflects an interactive effect between soil properties and WFPS. Conclusion/Significance Our results indicated that improved fertilizer and soil management have the potential to maintain highly productive corn yield while reducing greenhouse gas emissions.

Heavy metals in summer squash fruits grown in soil amended with municipal sewage sludge.

The increasing awareness of the value of vegetables and fruits in the human diet requires monitoring of heavy metals in food crops. The effects of amending soil with compost made from municipal sewage sludge (MSS) and MSS mixed with yard waste (MSS-YW) on Cd, Cr, Mo, Cu, Zn, Pb, and Ni concentrations in soil and the potential bioaccumulation of heavy metals in squash fruits at harvest were investigated. A field study was conducted in a silty-loam soil at Kentucky State University Research Farm. Eighteen plots of 22 × 3.7 m each were separated using metal borders and the soil in six plots was mixed with MSS at 15 t acre−1, six plots were mixed with MSS-YW at 15 t acre−1 (on dry weight basis), and six unamended plots (no-mulch) were used for comparison purposes. Plots were planted with summer squash and heavy metals were analyzed in soil and mature fruits at harvest. Analysis of heavy metals in squash fruits was conducted using inductively coupled plasma spectrometry. Zinc and Cu concentrations in soil mixed with MSS were extremely high compared to other metals. In squash fruits, concentrations of Zn were generally greater than Cu. Total squash marketable yield was greatest in MSS-YW and MSS treatments compared to no-mulch conventional soil. Concentrations of Cd and Pb in soil amended with MSS averaged 0.1 and 1.4 mg kg−1, respectively. These levels were much lower than the limits in the U.S. guidelines for using MSS in land farming. Data revealed that maximum concentrations of Cd and Pb in squash fruits were 0.03 and 0.01 μ g g−1 dry fruit, respectively. Nickel concentration in squash fruits fluctuated among harvest dates reaching a maximum of 2.5 μ g g−1 dry fruit. However, these concentrations were far below their permissible limits in edible fruits.

Responses of corn physiology and yield to six agricultural practices over three years in middle Tennessee.

Different agricultural practices may have substantial impacts on crop physiology and yield. However, it is still not entirely clear how multiple agricultural practices such as tillage, biochar and different nutrient applications could influence corn physiology and yield. We conducted a three-year field experiment to study the responses of corn physiology, yield, and soil respiration to six different agricultural practices. The six treatments included conventional tillage (CT) or no tillage (NT), in combination with nitrogen type (URAN or chicken litter) and application method, biochar, or denitrification inhibitor. A randomized complete block design was applied with six replications. Leaf photosynthetic rate, transpiration, plant height, leaf area index (LAI), biomass, and yield were measured. Results showed that different agricultural practices had significant effects on plant leaf photosynthesis, transpiration, soil respiration, height, and yield, but not on LAI and biomass. The average corn yield in the NT-URAN was 10.03 ton/ha, 28.9% more than in the CT-URAN. Compared to the NT-URAN, the NT-biochar had lower soil respiration and similar yield. All variables measured showed remarkable variations among the three years. Our results indicated that no tillage treatment substantially increased corn yield, probably due to the preservation of soil moisture during drought periods.

Simulated Regional PM10 Dispersion from Agricultural Tilling Operations Using HYSPLIT

Particulate matter (PM) of aerodynamic diameter less than or equal to 10 µm (PM10) is regulated by the U.S. Environmental Protection Agency (EPA) as part of the National Ambient Air Quality Standards (NAAQS). This article reports on the calibration and evaluation of the HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) version 4.9 model to simulate regional dust dispersion from a disking operation. Disking operations in a cotton field in Las Cruces, New Mexico, were conducted, and boundary layer PM10 concentrations were sampled using a DustTrak sampler on an airplane flown at altitudes between 200 and 500 m and several kilometers downwind. Using North American Mesoscale (NAM) forecast meteorological data (NAM12km, 12 km resolution) with vertical profiles, the model is capable of reasonably simulating regional PM10 dispersion (simulated data = 1.048 × measured data with R2 = 0.85).

Drench Treatments for Management of Larval Japanese Beetle (Coleoptera: Scarabaeidae) in Field-Grown Balled and Burlapped Nursery Plants

Abstract Insecticide drenches were applied to postharvest field-grown nursery plants harvested as 60-cm-diameter balled and burlapped (B&B) root balls for controlling third instars of Japanese beetle, Popillia japonica Newman (Coleoptera: Scarabaeidae). Bifenthrin, chlorpyrifos, lambda-cyhalothrin, and thiamethoxam were drench-applied in fall and spring tests at volumes of runoff (1×; ≈2.57 liters per drench per root ball) or twice runoff (2×). Tests also examined consecutive drenches (two, four, or six) and B&B rotation between drenches. Fall-applied drenches did not meet the Domestic Japanese Beetle Harmonization Plan (DJHP) standards of ≤1 grub and ranged from 0 to 90% control. However, most fall-applied drenches significantly reduced grub numbers relative to the untreated root balls. Spring-applied drenches were more effective than fall drenches: chlorpyrifos treatments gave 94–100% control, whereas other spring-applied treatments were less consistent, including thiamethoxam (83–100% control) and bifenthrin (61–100% control). Lambda-cyhalothrin was not effective. A higher drench volume (2×) did not significantly improve treatment efficacy; however, grub numbers decreased as the number of drenches increased for fall-applied chlorpyrifos and thiamethoxam and spring-applied bifenthrin. Rotation of root balls significantly reduced grub numbers compared with nonrotated treatments for fall-applied chlorpyrifos (six drenches) and bifenthrin (two or six drenches), but these treatments did not meet DJHP standards. The study indicates chlorpyrifos, bifenthrin, and thiamethoxam drenches can control Japanese beetle in the spring and may provide a new postharvest option to certify B&B plants for Japanese beetle.

Modeling PM10 Regional Transport from Disking Operations

Particulate matter (PM) of aerodynamic diameter less than or equal to 10 microns, PM10, is regulated by the U.S. Environmental Protection Agency (EPA) as part of the National Ambient Air Quality Standards (NAAQS). PM10 emitted from agricultural field operations (e.g., disking, listing, leveling, planting, harvesting) can be dispersed downwind in the far-field (i.e., > 1 km). This paper reports on the calibration and evaluation of the Hysplit4 (Hybrid Single-Particle Lagrangian Integrated Trajectory) model to simulate regional dust dispersion from a disking operation. Disking operations in a cotton field at Las Cruces, NM, were conducted, and boundary layer PM10 concentrations were sampled using a Dustrack™ sampler on an airplane flown at altitudes between 200 m and 550 m and downwind several kilometers. Based on the measured data, the model parameters of released particle number, grid size, and particle release height were calibrated. Using NAM12km meteorological data with vertical profiles, the model is capable of reasonably simulating regional PM10 dispersion (the simulated data =1.048×measured data with R2=0.85) when the PM10 was released at ground level. However, using measured point meteorological data at ground level and when the simulated particles were released at ground level, the model error was 90%. The smaller simulated values may be caused by the model’s inability to capture the surface layer micrometeorology that transports ground-level dusts to higher altitudes. When using ground measurements of meteorological data, different release heights (50, 100, 150, and 200 m) of the particles were tested, and at the release height of 200 m (top of surface layer), the model performance was the best - the error was 10%, and the R2 was 0.65.