Ann-Marie Fortuna

Links among Nitrification, Nitrifier Communities, and Edaphic Properties in Contrasting Soils Receiving Dairy Slurry

Soil biotic and abiotic factors strongly influence nitrogen (N) availability and increases in nitrification rates associated with the application of manure. In this study, we examine the effects of edaphic properties and a dairy (Bos taurus) slurry amendment on N availability, nitrification rates and nitrifier communities. Soils of variable texture and clay mineralogy were collected from six USDA-ARS research sites and incubated for 28 d with and without dairy slurry applied at a rate of ~300 kg N ha(-1). Periodically, subsamples were removed for analyses of 2 M KCl extractable N and nitrification potential, as well as gene copy numbers of ammonia-oxidizing bacteria (AOB) and archaea (AOA). Spearman coefficients for nitrification potentials and AOB copy number were positively correlated with total soil C, total soil N, cation exchange capacity, and clay mineralogy in treatments with and without slurry application. Our data show that the quantity and type of clay minerals present in a soil affect nitrifier populations, nitrification rates, and the release of inorganic N. Nitrogen mineralization, nitrification potentials, and edaphic properties were positively correlated with AOB gene copy numbers. On average, AOA gene copy numbers were an order of magnitude lower than those of AOB across the six soils and did not increase with slurry application. Our research suggests that the two nitrifier communities overlap but have different optimum environmental conditions for growth and activity that are partly determined by the interaction of manure-derived ammonium with soil properties.

The role of biochar porosity and surface functionality in augmenting hydrologic properties of a sandy soil

This paper reports studies to elucidate the potential relationships between porosity and surface functionality of biochar and soil water retention characteristics. The biochars studied were produced from pine wood (PW), hybrid poplar wood (HP), and pine bark (PB) at temperatures of 350°C and 600°C. The resulting materials were then oxidized under air at 250°C to generate oxygenated functional groups on the surface. All biochar were thoroughly characterized (surface and bulk properties) and their hydrological properties measured in blends with Quincy sand. We prepared 39 microcosms for this study to examine the effect of biochar functionalities and porosity on the hydro-physical properties of Quincy sand. Each biochar was thoroughly mixed with the soil at 20gkg-1. The field capacity, wilting point, and total available soil moisture of the bio-char/Quincy sand mixtures were measured for both dry and wet ranges. The soil water potentials and soil water contents were fitted using the model of van Genuchten. Our results indicated that the amount of oxygenated functional groups on the surface of biochars clearly differentiated the biochars in terms of hydrophilicity, with the oxidized biochars being superior, followed by the low-temperature biochars, while the high temperature biochars possessed lowest hydrophilicity. As a result, oxidized biochars exhibited better wettability compared to unoxidized biochars, regardless their feedstock source. Significant correlation occurred between the total acidic functional groups on biochar surface and water contents at different matric potentials. Over a wide range of soil water potentials, oxidized biochar-soil mixtures held more water than the unoxidized biochar-soil mixtures except in the region between -0.1 and -5kPa of ψ, which is near saturation. Soil water contents at different matric potentials were significantly inter-correlated (P<0.01) and correlated with bulk densities of biochar-amended soil samples.

Biosolids applications to tall fescue have long-term influence on soil nitrogen, carbon, and phosphorus.

Repeated applications of biosolids provide long-term benefits by increasing soil organic matter and N supply but can cause excess accumulation of P. Our objective was to determine the residual effects of repeated surface applications of biosolids on N availability and fate, tall fescue ( Schreb.) response, soil C, and P. A field experiment was started in 1993 to compare two biosolids products, each applied at three rates (6.7, 13.4, and 20.1 Mg ha yr), with synthetic N fertilizer (0 and 403 kg N ha yr as ammonium nitrate). Treatments were surface applied for 10 yr, followed by a 9-yr residual period where all plots received a reduced rate of inorganic N (202 kg N ha yr). Annual measurements included forage yield, N uptake, and soil nitrate N. Soil samples collected in 2002 and 2011 were analyzed for total C and N and Bray-1 P. Cumulative apparent N recoveries in harvested grass (1993-2010) were 51% for biosolids N and 72% for ammonium nitrate. Net fall soil nitrate N summed for the period 1993-2002 ranged from <1 to 3% of N applied. The N applied that was accounted for in forage and soil averaged 74% for biosolids and 73% for ammonium nitrate. Soil C increased in the biosolids treatments, and the increase was equivalent to 27% of biosolids C. Bray-1 P remained at excessive levels (338-629 mg P kg soil) 9 yr after the last biosolids application.

Long-Term Crop and Soil Response to Biosolids Applications in Dryland Wheat

Biosolids have the potential to improve degraded soils in grain-fallow rotations. Our objectives were to determine if repeated biosolids applications in wheat ( L.)-fallow could supply adequate but not excessive N for grain production and increase soil C without creating a high risk of P loss. A replicated on-farm experiment was established in 1994 in central Washington, comparing anaerobically digested biosolids with anhydrous NH and a zero-N control. Biosolids were applied at 5, 7, and 9 Mg ha every fourth year through 2010 and incorporated 10 cm deep, while anhydrous NH plots received 56 kg ha N every second year. Grain yield and protein were determined. Soil chemical, biological, and bulk density analyses were made in 2012. Medium and high biosolids rates significantly increased grain yield (3.63 vs. 3.13 Mg ha) and protein (103 vs. 85 g kg) compared with anhydrous NH averaged across all crops. The medium biosolids rate had significantly lower bulk density (1.05 vs. 1.22 g kg) and greater total C (0-10-cm depth) (16.9 vs. 9.4 g kg), mineralizable N (156 vs. 52 mg kg), and extractable P (114 vs. 16 mg kg) than anhydrous NH. The P index site vulnerability increased from low for anhydrous NH to medium for the biosolids treatments. Soil NO-N was nearly always <10 mg N kg soil (0-30-cm depth). Medium and high biosolids rates significantly increased bacteria/fungi ratios, Gram-negative bacteria, and anaerobic bacteria markers compared with anhydrous NH. Biosolids can be an agronomically and environmentally sound management practice in wheat-fallow systems.

Using NIRS to predict fiber and nutrient content of dryland cereal cultivars.

Residue from cultivars of spring wheat (Triticum aestivum L.), winter wheat, and spring barley (Hordeum vulgare L.) was characterized for fiber and nutrient traits using reference methods and near-infrared spectroscopy (NIRS). Calibration models were developed for neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL), carbon (C), sulfur (S), nitrogen (N), and C:N. When calibrations were tested against validation sets for each crop year, NIRS was an acceptable method for predicting NDF (standard error of prediction (SEP)<0.87; R2>0.90) and ADF (SEP< 0.81; R2>0.92) and moderately successful for ADL in 1 year of the study (SEP=0.44; R2=0.81) but less successful for C, S, N, and C:N (R2 all<0.57). These results indicate that NIRS can predict the NDF and ADF of cereal residue from dryland cropping systems and is a useful tool to estimate residue decomposition potential.

Gaseous Nitrogen and Bacterial Responses to Raw and Digested Dairy Manure Applications in Incubated Soil

A study was conducted under laboratory conditions to compare rates of nitrous oxide (N(2)O) and ammonia (NH(3)) emissions when soil was amended with anaerobically digested dairy manure slurry containing <30% food byproducts, raw dairy manure slurry, or urea. Slurries were applied via surface and subsurface methods. A second objective was to correlate genes regulating nitrification and denitrification with rates of N(2)O production, slurry treatment, and application method. Ammonia volatilization from incubated soil ranged from 140 g kg(-1) of total N applied in digested slurry to 230 g kg(-1) in urea. Subsurface application of raw dairy manure slurry decreased ammonia volatilization compared with surface application. Anaerobic digestion increased N(2)O production. Cumulative N(2)O loss averaged 27 g kg(-1) of total N applied for digested slurry, compared with 5 g kg(-1) for raw dairy slurry. Genes of interest included a 16S rRNA gene selective for β-subgroup proteobacterial ammonia-oxidizers, amoA, narG, and nosZ quantified with quantitative polymerase chain reaction (qPCR) and real-time polymerase chain reaction (RT-PCR). Application of anaerobically digested slurry increased nitrifier and denitrifier gene copies that correlated with N(2)O production. Expression of all genes measured via mRNA levels was affected by N applications to soil. This study provides new information linking genetic markers in denitrifier and nitrifier populations to N(2)O production.

Influence of Seeding Ratio, Planting Date, and Termination Date on Rye-Hairy Vetch Cover Crop Mixture Performance under Organic Management

Cover crop benefits include nitrogen accumulation and retention, weed suppression, organic matter maintenance, and reduced erosion. Organic farmers need region-specific information on winter cover crop performance to effectively integrate cover crops into their crop rotations. Our research objective was to compare cover crop seeding mixtures, planting dates, and termination dates on performance of rye (Secale cereale L.) and hairy vetch (Vicia villosa Roth) monocultures and mixtures in the maritime Pacific Northwest USA. The study included four seed mixtures (100% hairy vetch, 25% rye-75% hairy vetch, 50% rye-50% hairy vetch, and 100% rye by seed weight), two planting dates, and two termination dates, using a split-split plot design with four replications over six years. Measurements included winter ground cover; stand composition; cover crop biomass, N concentration, and N uptake; and June soil NO3 --N. Rye planted in mid-September and terminated in late April averaged 5.1 Mg ha-1 biomass, whereas mixtures averaged 4.1 Mg ha-1 and hairy vetch 2.3 Mg ha-1. Delaying planting by 2.5 weeks reduced average winter ground cover by 65%, biomass by 50%, and cover crop N accumulation by 40%. Similar reductions in biomass and N accumulation occurred for late March termination, compared with late April termination. Mixtures had less annual biomass variability than rye. Mixtures accumulated 103 kg ha-1 N and had mean C:N ratio <17:1 when planted in mid-September and terminated in late April. June soil NO3 --N (0 to 30 cm depth) averaged 62 kg ha-1 for rye, 97 kg ha-1 for the mixtures, and 119 kg ha-1 for hairy vetch. Weeds comprised less of the mixtures biomass (20% weeds by weight at termination) compared with the monocultures (29%). Cover crop mixtures provided a balance between biomass accumulation and N concentration, more consistent biomass over the six-year study, and were more effective at reducing winter weeds compared with monocultures.

Comparison of Raw Dairy Manure Slurry and Anaerobically Digested Slurry as N Sources for Grass Forage Production

We conducted a 3-year field study to determine how raw dairy slurry and anaerobically digested slurry (dairy slurry and food waste) applied via broadcast and subsurface deposition to reed canarygrass (Phalaris arundinacea) affected forage biomass, N uptake, apparent nitrogen recovery (ANR), and soil nitrate concentrations relative to urea. Annual N applications ranged from 600 kg N ha−1 in 2009 to 300 g N ha−1 in 2011. Forage yield and N uptake were similar across slurry treatments. Soil nitrate concentrations were greatest at the beginning of the fall leaching season, and did not differ among slurry treatments or application methods. Urea-fertilized plots had the highest soil nitrate concentrations but did not consistently have greatest forage biomass. ANR for the slurry treatments ranged from 35 to 70% when calculations were based on ammonium-N concentration, compared with 31 to 65% for urea. Slurry ANR calculated on a total N basis was lower (15 to 40%) due to lower availability of the organic N in the slurries. No consistent differences in soil microbial biomass or other biological indicators were observed. Anaerobically digested slurry supported equal forage production and similar N use efficiency when compared to raw dairy slurry.

Potential carbon sequestration and nitrogen cycling in long-term organic management systems

The fertility and soil health of organic agroecosystems are determined in part by the size and turnover rate of soil carbon (C) and nitrogen (N) pools. Our research contrasts the effects of best management practices (BMP) (reduction in soil disturbance, addition of organic amendments) on C and N cycling in soils from two field sites representing five organic agroecosystems. Total soil organic C (SOC), a standard measure of soil health, contains equal amounts of biologically and non-biologically active C that is not associated with release of mineral N. A three-pool first-order model can be used to estimate the size and turnover rates of C pools but requires data from a long-term incubation. Our research highlights the use of two rapid C fractions, hydrolysable and permanganate (0.02 M) oxidizable C, to assess shifts in biologically active C. Adoption of BMP in organic management systems reduced the partitioning of C to the active pool while augmenting the slow pool C. These pools are associated with potentially mineralizable N supplied by residues, amendments and soil organic matter affecting the concentration and release of mineral N to crops. Our data show that minimizing disturbance (no tillage, pasture) and mixed compost additions have the potential to reduce carbon dioxide emissions while enhancing slow pool C and or its turnover, a reservoir of nutrients available to the soil biota. Use of these rapid, sensitive indicators of biological C activity will aid growers in determining whether a BMP fosters nutrient loss or retention prior to shifts in total SOC.

Characterization of zinc oxide nanoparticle (nZnO) alginate beads in reducing gaseous emission from swine manure

ABSTRACT Hydrogen sulfide (H2S) and greenhouse gases’ emission from livestock production facilities are of concern to human welfare and the environment. Application of nanoparticles (NPs) has emerged as a potential option for minimizing these gaseous emissions. Application of bare NPs, however, could have an adverse effect on plants, soil, human health, and the environment. To minimize NPs’ exposure to the environment by recovering them, NPs were entrapped in polymeric beads for treating livestock manure. The objectives of the research were to understand the mechanism of gaseous reduction in swine manure treated for 33 days with zinc oxide nanoparticles (nZnO) or nZnO-entrapped alginate (alginate-nZnO) beads by different characterization techniques. Headspace gases from treated manure flasks were collected in 2–6-day intervals during the experimental period and were analyzed for methane (CH4), carbon dioxide (CO2), and H2S concentrations. The microbial analysis of manure was carried out using bacterial plate counts and Real-Time Polymerase Chain Reaction methods. Morphology and chemical composition of alginate-nZnO beads were analyzed by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and X-ray Photoelectron Spectroscopy (XPS). Alginate-nZnO beads or bare nZnO proved to be an effective NP in reducing H2S (up to 99%), CH4 (49–72%), and CO2 (46–62%) from manure stored under anaerobic conditions and these reductions are likely due to the microbial inhibitory effect from nZnO, as well as chemical conversion. Both SEM-EDS and XPS analysis confirmed the presence of zinc sulfide (ZnS) in the beads, which is likely formed by reacting nZnO with H2S.