Raw Dairy Manure Research Articles

Optimization of Ammonia Nitrogen Removal and Recovery from Raw Liquid Dairy Manure Using Vacuum Thermal Stripping and Acid Absorption Process: A Modeling Approach Using Response Surface Methodology

Dairy manure adds a substantial amount of nitrogen to wastewater due to its high levels of associated nutrients. Removal and recovery of ammonia nitrogen (NH3-N) from raw liquid dairy manure (RLDM) is greatly valued. This study was focused on the vacuum thermal stripping–acid absorption (VTS-AA) process for NH3-N from RLDM, followed by modeling and optimization. Using the response surface methodology (RSM)-based central composite design (CCD) approach, the critical operational parameters of the vacuum thermal stripping process, including temperature (50–70 °C), pH (9–11), vacuum pressure (35–55 kPa), and treatment time (60–90 min), were optimized. With the specified parameters set at temperature 69.9 °C, pH 10.5, vacuum pressure 53.5 kPa, and treatment time 64.2 min, the NH3-N removal efficiency attained was 98.58 ± 1.05%, aligning closely with the model prediction. Furthermore, the recovered ammonium sulfate ((NH4)2SO4) closely matched their commercial counterparts, confirming the effectiveness of the VTS-AA process in recovering NH3-N from RLDM. The distinct advantage of the employed technology lies in the concurrent energy demand reduction achieved by introducing a vacuum system. These findings contribute valuable insights into the practical implementation of the VTS-AA process for treating raw dairy manure, particularly in large-scale operational contexts.

Microalgae-bacteria consortia for the treatment of raw dairy manure wastewater using a novel two-stage process: Process optimization and bacterial community analysis

The major objective of this study was to develop a functional microalgae-bacteria consortium for the treatment of dairy manure wastewater (DMW). Chlorella sorokiniana AK-1 was selected as the proficient microalgal strain for treating unsterilized DMW. AK-1 was directly grown in 50% raw DMW, and the addition of an acclimated mixed bacterial culture enriched from dairy manure improved treatment efficiency. Culture conditions for DMW treatment using the AK-1 mixed bacterial consortium were optimized as follows: 50% raw DMW, 0.4 g/L mixed bacterial inoculum on day 1, followed by 0.1 g/L AK-1 inoculum on day 3, and further incubation for 3 days. The achieved removal efficiencies for COD, BOD, TN, NH3-N, and TP were 84.3%, 97.8%, 90.2%, 99.1%, and 100%, respectively. Bacterial 16S rDNA sequencing was conducted to analyze the shift in the bacterial community during wastewater treatment. In DMW, Firmicutes emerged as the dominant phylum, whereas Proteobacteria took over after microalgal inoculation. Additionally, Actinobacteria and Bacteroidetes were consistently present in all samples. Interestingly, Patescibacteria and Planctomycetes were found in varying proportions. At the species level, the predominant bacteria identified during the treatment process were Rhizobiaceae, Sericytochromatia_unclassified, Pirellula_sp, Owenweeksia, Devosia_unclassified, Acinetobacter_towneri, and Acinetobacter_unclassified. Despite the significant diversity of the microbial community among the different processes, optimal microalgal biomass production and maximum nutrient removal efficiencies were achieved using this designer microalgae-bacteria consortium.

Biofertilizer derived from dairy manure increases raspberry fruit weight and leaf magnesium concentration

Dairy manure is often readily available in the area where the processed red raspberry industry is concentrated. The successful transformation of raw dairy manure waste to a valuable organic-derived fertilizer could alleviate environment threats and provide multiple soil health benefits. The value of raw dairy manure could be enhanced through new technologies that composts, blends, and pelletizes manure into a concentrated form. However, the potential benefits of this alternative manure-derived fertilizer have not been characterized in any commercial crop. The objective of this project is to evaluate the effects of composted, blended, and pelletized manure (i.e., CBP) on raspberry growth and production. Treatments of urea and CBP fertilizers blended with 10% and 20% (w/w) canola meal were surface applied at low and high rates (56 and 90 kg N ha−1, respectively) to an established ‘Meeker’ raspberry field 2020 and 2021 in a randomized complete block design with three replications. Plant growth and productivity variables were analyzed. The utilization of CBP with 20% or 10% canola meal enhanced fruit weight and leaf magnesium concentration compared to urea, respectively. CBP fertilizers decreased leaf manganese concentration more than urea. There were no other fertilizer source treatment effects for all other measured variables. Additionally, there were no fertilizer rate effects for total yield, fruit quality, plant growth, and leaf nutrient concentrations. Based on the results, CBP fertilizer did not compromise plant growth and productivity relative to urea and could be an alternative to conventional fertilizer .

Microbial Safety of Dairy Manure Fertilizer Application in Raspberry Production.

Dairy manure, a by-product in the dairy industry, is also a potential source of nutrients for crops. However, improper application of biological soil amendments of animal origin can be a source of contamination with enteric foodborne pathogens. A 2-year field study was conducted to evaluate impacts of dairy manure fertilizer application on the microbial safety of red raspberry (Rubus idaeus L) production. Fertilizers, including a standard synthetic fertilizer (CON), straight lagoon raw manure (SL), anaerobically digested liquid effluent (DLE), compost (COM) and dairy manure-derived refined fertilizers including ammonium sulfate (AS) and phosphorous solid (PS), were randomly applied in quadruplicate to raspberry plots. Soil, fertilizer, foliar, and raspberry fruit samples were collected during the cropping season for the quantification of indicator microorganisms (total coliform and generic Escherichia coli) and detection of important foodborne pathogens (Shiga toxin-producing E. coli (STEC), Salmonella, and Listeria monocytogenes). Counts of total coliforms in soil were stable over the 2017 cropping season and were not impacted by fertilizer application. In 2018, total coliforms increased with season and soils treated with COM had a significantly higher coliform number than those treated with CON. Both total coliform and generic E. coli in raspberry fruit samples were below the detectable level (3 most probable number/g) regardless of fertilizer types. In both years, no STEC or L. monocytogenes was detected from any of the collected samples regardless of fertilizer treatments. However, Salmonella were detected in some of the fertilizers, including PS (2017), DLE (2018), and SL (2018), which were transferred to soil samples taken directly after application of these fertilizers. Salmonella were not detected in soil samples 2 or 4 months post fertilizer application, foliar, or raspberry fruit samples regardless of fertilizer applications. In summary, one-time application of raw dairy manure or dairy manure-derived fertilizers more than 4 months prior to harvest has no major impact on food safety of red raspberry (6 ft. tall) production in Lynden sandy loam under good agricultural practices.

Fate of Pirlimycin and Antibiotic-Resistant Fecal Coliforms in Field Plots Amended with Dairy Manure or Compost during Vegetable Cultivation.

Identification of agricultural practices that mitigate the environmental dissemination of antibiotics is a key need in reducing the prevalence of antibiotic-resistant bacteria of human health concern. Here, we aimed to compare the effects of crop (lettuce [ L.] or radish [ L.]), soil amendment type (inorganic fertilizer, raw dairy manure, composted dairy manure, or no amendment), and prior antibiotic use history (no antibiotics during previous lactation cycles vs. manure mixed from cows administered pirlimycin or cephapirin) of manure-derived amendments on the incidence of culturable antibiotic-resistant fecal coliforms in agricultural soils through a controlled field-plot experiment. Antibiotic-resistant culturable fecal coliforms were recoverable from soils across all treatments immediately after application, although persistence throughout the experiment varied by antibiotic class and time. The magnitude of observed coliform counts differed by soil amendment type. Compost-amended soils had the highest levels of cephalosporin-resistant fecal coliforms, regardless of whether the cows from which the manure was derived were administered antibiotics. Samples from control plots or those treated with inorganic fertilizer trended toward lower counts of resistant coliforms, although these differences were not statistically significant. No statistical differences were observed between soils that grew leafy (lettuce) versus rooted (radish) crops. Only pirlimycin was detectable past amendment application in raw manure-amended soils, dissipating 12 to 25% by Day 28. Consequently, no quantifiable correlations between coliform count and antibiotic magnitude could be identified. This study demonstrates that antibiotic-resistant fecal coliforms can become elevated in soils receiving manure-derived amendments, but that a variety of factors likely contribute to their long-term persistence under typical field conditions.

Patterns of dairy manure management in China

Abstract: The dairy industry in China is rapidly developing, particularly in terms of the upscaling of dairy farms. However, nutrient-rich manure brings challenges to the sustainability of the dairy industry. This study investigated and reviewed the patterns of dairy manure management in China, and the results indicate that dairy manure could be used as an organic fertilizer because of its high organic nutrient content and low metal content. However, legislation prohibits the application of untreated (raw) dairy manure. An existing technology for handling animal slurry is the separation into a liquid and a solid manure fraction. The solid fraction can be used as compost and bedding materials, and it has limited environmental risk. However, the emissions from the storage of liquid manure need further attention. The cycle of manure production, collection, transportation, separation and storage can only be closed if the nutrients are eventually applied to grass and arable land according to crop needs. Therefore, distribution of knowledge on nutrient levels, crop needs and nutrient management plans, supported by legislation on maximum application standards, is needed. In this way, an environmentally friendly development of dairy manure management might be possible. Keywords: dairy manure, manure handling pattern, legislation, nutrient recycling, emissions DOI: 10.3965/j.ijabe.20171003.3048 Citation: Li C Y, Qiao W, Melse R W, Li L J, de Buisonje F E, Wang Y J, et al. Patterns of dairy manure management in China. Int J Agric & Biol Eng, 2017; 10(3): 227–236.

ANAEROBICALLY DIGESTED DAIRY MANURE AS AN ALTERNATIVE NITROGEN SOURCE TO MITIGATE NITROUS OXIDE EMISSIONS IN FALL-FERTILIZED CORN

Anaerobically digested dairy manure (AD) has been proposed as an alternative nitrogen source to reduce soil nitrous oxide (N2O) emissions compared with raw dairy manure (RM). The aim of this research was to compare soil N2O emissions associated with AD and RM according to three application methods: surface broadcasting (SB), incorporation (SBI), and injection (INJ). The field experiment was conducted on a loam soil at Elora, ON, from November 2012 to November 2014, using a randomized block design with four replications. Manure was applied in mid-November (fall), and corn (Zea mays) was planted in late-May of each year. Nitrous oxide flux was measured using nonsteady state chambers sampled weekly or bi-weekly. Cumulative N2O emissions were significantly affected by the interaction between source and method (F = 3.99, P < 0.01), with the highest value for surface broadcast AD (6.4 kg N2O-N ha−1) and the lowest value for injected AD (2.6 kg N2O-N ha−1). Manure source affected cumulative N2O emissions (F = 4....

Field Nitrogen Losses Induced by Application Timing of Digestate from Dairy Manure Biogas Production.

Anaerobic digestion of dairy manure has environmental benefits, but the impact of effluent (i.e., digestate [DG]) application on environmental nitrogen (N) losses from soils has not been well quantified. Our objective was to evaluate how field application of DG affected nitrous oxide (NO) emissions and nitrate (NO) leaching compared with raw dairy manure (RM) in spring versus fall applications. We measured N losses year-round for 2.5 yr in silage corn on tile-drained clay soil in Alfred, Ontario, Canada. Treatments were: digestate applied in spring (DS) and fall (DF), raw dairy manure applied in spring (RS) and fall (RF), urea applied in spring, and a control. Overall, the source of N had no effect on annual NO emissions (overall average DG and RM, 4.9 kg NO-N ha yr), but more NO leached from DS than RS treatments (8.8 and 4.8 kg NO-N ha yr on average, respectively). Estimated indirect NO emissions from leached NO-N were small (<0.2 kg NO-N ha yr). Timing of application did not affect annual NO emissions but did shift emissions to the non-growing season for fall applications (65% on average) and to the growing season for spring applications (60% on average). Overall environmental N losses (NO-N + NO-N) from DG were similar to RM when applied at the same time. For the conditions of our study, downstream emissions from anaerobic digestion (i.e., emissions induced by applied digestate) do not present an adverse trade-off to the environmental benefits incurred during the biogas production phase.

Occurrence and Dispersal of Indicator Bacteria on Cucumbers Grown Horizontally or Vertically on Various Mulch Types

No data exist on the impact of cultivation practices on food safety risks associated with cucumber. Cucumbers are typically grown horizontally over a mulch cover, with fruit touching the ground, but this vining plant grows well in vertical systems. To assess whether production system affects bacterial dispersal onto plants, field trials were conducted over 2 years. Cucumber cultivar 'Marketmore 76' was grown horizontally on plastic, straw, or bare ground or vertically on trellises installed on bare ground in soil previously amended with raw dairy manure. Fruit, flower, leaf, and soil samples were collected to quantify Escherichia coli , thermotolerant coliforms, and enterococci by direct plating. E. coli isolates were characterized by BOX-PCR to evaluate relatedness among strains. Although thermotolerant coliforms and enterococci were significantly less abundant on fruit in year 1 (P < 0.05), this result was not seen in year 2 when more rain was recorded. Instead, fruit from straw-mulched beds had higher levels of enterococci compared with fruit grown on bare ground (P < 0.05). Leaves on bare ground occasionally had more bacteria than did leaves on plastic mulch beds (P < 0.05). Production system did not impact flower-associated bacterial levels. E. coli isolates (n =127) were genotyped, generating 21 distinct fingerprints. Vertical production did not appear to be a barrier for E. coli dispersal to the crop, as suggested by numerous related isolates from soil and flowers on bare ground, straw-mulched, and trellised beds (subcluster B1). None of the isolates from soil and flowers in this subcluster were related to isolates recovered from fruit, showing that flower colonization does not necessarily lead to fruit colonization. One cluster of isolates contained those from flowers and fruits but not soil, indicating a source other than manure-amended soil. Straw may be a source of E. coli ; a number of closely related E. coli isolates were retrieved from soil and fruits from straw-mulched beds. Our approach revealed E. coli dispersal patterns and could be used to assess bacterial transmission in other production systems.

Bioenergy production from algae using dairy manure as a nutrient source: Life cycle energy and greenhouse gas emission analysis

Abstract This study estimated the potential of algal bioenergy production using nitrogen and phosphorus present in the dairy manure (produced in the US). State wise dairy manure production and energy mixes were used to estimate algal bioenergy production and associated life cycle nonrenewable primary energy demand and greenhouse gas emissions for the four scenarios. These scenarios were constructed using various combination of following processes (i) anaerobic digestion, (ii) algal biodiesel production using effluent from (i), (iii) pyrolysis, and (iv) enzymatic hydrolysis. Bioenergy production, nonrenewable primary energy demand and greenhouse gas emissions of each state were aggregated to estimate the total bioenergy production, nonrenewable primary energy requirement and greenhouse gas emissions for the US. Two different cases were simulated for each scenario, one without taking into account the nutrient values (N, P) of applied sludge generated from the bioenergy production (Case B) while in the other one, nutrient values of sludge were considered (Case A). For incorporation of nutrient values of sludge, system expansion approach was used. It was estimated that by using dairy manure, 0.56 billion GJ/yr bioenergy could be produced. Minimum “nonrenewable primary energy requirement (NRPER)” (GJ/GJ) [Total primary nonrenewable energy requirement/bioenergy produced] and GHG emissions (kg CO2 eq./GJ bioenergy produced) for the four scenarios (1–4) for case B were as follows (1) 0.37, 27 (2) 0.51, −30; (3) 0.55, 47 and (4) 0.70, 15 respectively. In case A, NRPER did not change as compared to case B. GHG emissions increased in case A scenarios as compared to case B scenarios. The increase in GHG emission was mostly due to incorporation of reference scenario (raw dairy manure was applied on the ground) and N2O emission from the sludge amended soil.

Effect of Manure Treatment on Ammonia Emission during Storage under Ambient Environment

The effect of anaerobic digestion (AD), coarse solids removal, and a manure additive More Than ManureTM (MTMTM) on ammonia (NH3) emission from raw (Non AD) dairy manure and AD manure was studied during 110 days of storage. The study consisted of eight treatments in duplicate: AD manure and non AD manure, with and without coarse solids, and with and without MTMTM additive. These studies were conducted in a naturally ventilated barn. The nitrogen content of manure, especially the ammoniacal nitrogen, played an important role in NH3 emission. During the first 11 weeks of the storage, AD manure had significantly greater peak (33 to 38 ppm) concentrations of NH3, and NH3 fluxes (94 to 130 μg min−1 m−2) compared to raw manure (14 to 25 ppm and 55 to 81 μg min−1 m−2, respectively). From the 11th week until the end of storage, there was no significant difference in NH3 emissions across the manure treatments. The presence of course solids resulted in significanlty less peak NH3 for non AD manure when data were evaluated for the whole storage period. The manure additive MTMTM did not have a significant effect on NH3 emissions during storage, however, temperature was positively related to NH3 emissions. Total ammoniacal nitrogen and solids concentration in manure was the most important factors affecting NH3 emissions during storage.

Organic Amendment and Transitional Cropping System Effects on Crop Diseases

Organic inputs have been suggested to have either suppressive or conducive effects on levels of plant diseases. In this study, we compared effects of organic matter amendments and transitional cropping systems on plant diseases during the transition from conventional to organic agricultural production and 2 yr following. During the 3‐yr transition, organic amendments included raw dairy manure, composted dairy manure, and non‐amended treatment superimposed on three cropping systems (perennial pasture, cash grain crops, and vegetable crops). Two years of post‐transition crops included tomato (Lycopersicon esculentum Mill.) and bell pepper (Capsicum annuum L. var. annuum) in the first year and soybean [Glycine max (L.) Merr.] in the second. During transition, raw manure amendments resulted in higher levels of diseases caused by some biotrophic pathogens, including rusts in corn (Zea mays L.) and orchardgrass (Dactylis glomerata L.). However, raw manure applications were also found to suppress some diseases caused by necrotrophic pathogens, including anthracnose and Septoria leaf spot in tomato. Manure applications promoted higher soybean yields. Powdery mildew of cucurbits (Curbubita moschata Duchesne) was suppressed by composted manure. After transition, tomato plants grown in plots previously under the vegetable system had the highest levels of anthracnose, and soybean grown in plots previously in the pasture system had the highest levels of bacterial pustule, despite the fact that these same plots produced the highest yields in soybean. Yield benefits resulting from applications of raw manure to a pasture transition system may be attractive for farmers, but disease management strategies will need to be considered to prevent increased disease levels.

Nematode indicators as integrative measures of soil condition in organic cropping systems

Even though indicators based on nematode community composition are among the best developed metrics of soil health, little research has been done to support their application to management. This work tested the hypothesis that organic farming systems could enhance nematode community structure where soil resource condition had been enhanced by reducing disturbance and using organic fertility inputs. We tested this hypothesis by exploring the relationship between soil biology and the condition of the soil resource in an organic trial using the Nematode Maturity (MI), Plant Parasitic (PPI), Enrichment (EI), Channel (CI), and Structure (SI) indices. Shifts in nematode indices occurring during the growing season were compared with measures of labile soil organic matter and N availability [particulate organic matter-C and -N (POM-C, POM-N), particulate organic matter C:N ratio (POM C:N), potentially mineralizable N (PMN), hydrolysable N estimated with the Illinois-N test (IL-N), and heterotrophic activity estimated with fluorescein diacetate hydrolysis (FDA)]. Soil samples were collected four times during a single growing season from plots that had been transitioned from conventional to organic management under Ley-, Row Crop- and Vegetable-based regimes. Each of the three transition scenarios included three subplots that were either supplied with organic matter from raw and composted dairy manure or cover crop residues. High EI and low CI values revealed a greater dominance of the bacterial decomposition pathway in soils transitioned under the Ley system and values were positively associated with measures of microbial activity and available N. Increases in the PPI values were stimulated where nutrient availability (and likely crop root growth) were enhanced. The SI was positively associated with the POM fraction and declined after primary tillage. This signalled a shift in the community towards an early stage of succession and demonstrates the detrimental effects of tillage on soil food web complexity. Recommendations for soil stewardship that are guided by nematode food web indices would encourage practices that enhance soil organic matter, reduce the frequency of cultivation, and conserve structure.

The Effects of Microwave Pretreatment of Dairy Manure on Methane Production

This study was undertaken to evaluate the efficiency of a liquid-solids separation process and microwave pretreatment, as well as anaerobic biodegradability of microwave pretreated dairy manure. Liquid-solids separation of raw dairy manure resulted in solid and liquid fractions having different properties, with the solid fractions richer in total and volatile solids content and liquid fractions richer in nutrients and metal ions. Substantial amounts of soluble chemical oxygen demand and nutrients were released into the solution after the microwave treatment. The microwave pretreated dairy manure was also subjected to anaerobic digestion. The kinetic parameters of methane production potential, maximum methane production rate and lag time were determined using the modified Gompertz equation. Anaerobic digestion of liquid manure, without microwave treatment, outperformed the sets with microwave treatment. The microwave-treated liquid dairy manure, without acid addition had better results in terms of methane potential and methane production, than with acid addition. Thermophilic digestion exhibited a higher maximum methane production rate than that of mesophilic digestion, but lower methane yields. The microwave pretreatment of dairy manure resulted in high soluble chemical oxygen demand; however, methane yield was not increased.

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.

Waste Streams from Methane Digesters: Exporting Nutrients through Turfgrass and Forage Production Systems

Similar to manure, residual manure solids (MS) from methane digesters require cropping systems and management practices that optimize nutrient export to prevent large increases in soil P levels. The objectives were to compare forage and turfgrass sod production systems with respect to effects of MS management practices on soil properties and crop productivity and to compare mass balance of N and P on field scale. A 2‐yr field experiment was conducted on a fine sandy loam soil receiving MS to compare nutrient imports, forms in soil, and export by Tifton 85 bermudagrass (Cynodon spp.) grown for forage and Tifway bermudagrass [C. dactylon (L.) Pers. × C. transvaalensis (Burtt‐Davy)] grown for turfgrass sod. Five soil treatments for each crop included MS with and without Alum topdressed (250 kg total phosphorus [TP] ha−1) annually or a single application of MS (500 kg TP ha−1) incorporated compared to soil without MS. One harvest of Tifway sod removed 2.7 times more total nitrogen (TN) and 2.8 times more TP than three harvests of Tifton 85 forage biomass during the first year of production. Greater biomass production and nutrient uptake by Tifton 85 forage during the second production season reduced the difference in nutrient export between Tifton 85 and Tifway sod. Turfgrass sod production systems can be used by producers to increase export of MS applied nutrients compared to forage production and enable waste streams from methane digesters to be recycled.

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−1in 2009 to 300 g N ha−1in 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.

Earthworm abundance and species composition in organic forage production systems of northern Colorado receiving different soil amendments

We evaluated the effects of soil amendments on earthworm communities in organic annual forage and perennial pasture systems in northern Colorado. In the annual forage study (1) an annual warm season grass teff (Eragrostis tef) and (2) bare fallow were main plot treatments and received one of three soil amendments: (1) composted dairy manure (CDM), (2) raw dairy manure (RDM), and (3) no amendment as control. For the perennial pasture study, CDM was topdressed onto a grass mixture consisting of orchardgrass, smooth and meadow bromegrass at rates ranging from 0 to 44.8Mgha−1. At both sites, earthworm and soil samples were collected in July 2009. The earthworms identified from both systems were composed of endogeic species Aporrectodea rosea (Savigny), A. tuberculata (Eisen), and A. turgida (Eisen), the first being found only in the perennial pasture. In the annual forage study, earthworm total abundance did not differ between teff and bare fallow treatments. However, within bare fallow treatment, earthworm total abundance was significantly affected by soil amendment, with CDM averaging approximately 1.4 and 5.4 times greater earthworm total abundance than RDM and the control, respectively. Earthworm total abundance was found to be positively correlated with soil Cu (R=0.51, P=0.03) and K (R=0.58, P=0.01). In the perennial pasture, earthworm total abundance tended to increase with an increase in the CDM rate to 33.6Mgha−1. However, no further increase was observed when the CDM rate was increased to 44.8Mgha−1. At this site, earthworm total abundance was negatively correlated with EC (R=−0.37, P=0.02). Our results suggest that high quality (low C/N ratio) dairy manure is important for maintaining a high earthworm population. Larger CDM application rates appear to discourage earthworm populations probably due to salinity stress. Further study is necessary to elucidate the exact effects of manure quality and quantity on earthworm populations in annual forages and perennial pastures.

Redroot Pigweed (Amaranthus retroflexus) Seedling Emergence and Growth in Soils Amended with Composted Dairy Cattle Manure and Fresh Dairy Cattle Manure under Greenhouse Conditions

Organic soil amendments are known to affect the composition and density of annual weed communities. The objective of this research was to measure the effect on emergence and growth of redroot pigweed seedlings when soil was amended with composted dairy manure at 18, 36, and 54 T/ha, or with raw dairy manure at 41, 82, and 123 T/ha. Data recorded (1) seedling emergence over 12 days, (2) number of leaves and total leaf area, (3) shoot and root dry weight, and (4) seed number. Maximum seedling emergence (32%) occurred in nonamended soil (the control). Emergence declined in a linear fashion when soil was amended with manure or with compost. Compost additions affected seedling emergence more severely than did manure additions. For every measure of redroot pigweed growth except seed production, amendment with manure at 123 T/ha retarded growth compared to soil alone or compost-amended mixes. Manure applied at 82 T/ha reduced leaf area and plant height relative to other treatments. Growth of redroot pigweed in soil amended with compost at 36 and 54 T/ha was always equal to or greater than growth in soil that was not amended. Seed production in one of two runs of the experiment was more than double in soils amended with compost at 36 and 54 T/ha compared to the nonamended soil. These results suggest that amending soils with raw dairy manure may decrease the competitiveness of redroot pigweed, whereas amending with composted manure is likely to increase competitiveness.

Compost, Manure and Synthetic Fertilizer Influences Crop Yields, Soil Properties, Nitrate Leaching and Crop Nutrient Content

From 1993 to 2001, a maize-vegetable-wheat rotation was compared using either 1) composts, 2) manure, or 3) synthetic fertilizer for nitrogen nutrient input. From 1993 to 1998, red clover (Trifolium pratense L.) and crimson clover (Trifolium incarnatum L.) were used as an annual winter legume cover crop prior to maize production. From 1999 to 2001, hairy vetch (Vicia villosa Roth.) served as the legume green manure nitrogen (N) source for maize. In this rotation, wheat depended entirely on residual N that remained in the soil after maize and vegetable (pepper and potato) production. Vegetables received either compost, manure, or fertilizer N inputs. Raw dairy manure stimulated the highest overall maize yields of 7,395 kg/ha (approximately 140 bushels per acre). This exceeded the Berks County mean yield of about 107 bushels per acre from 1994 to 2001. When hairy vetch replaced clover as the winter green manure cover crop, maize yields rose in three of the four treatments (approximately 500-1,300 kg/ha, or 10-24 bu/a). Hairy vetch cover cropping also resulted in a 9-25 % increase in wheat yields in the compost treatments compared to clover cover cropping. Hairy vetch cover crops increased both maize and wheat grain protein contents about 16 to 20% compared to the clover cover crop. Compost was superior to conventional synthetic fertilizer and raw dairy manure in 1) building soil nutrient levels, 2) providing residual nutrient support to wheat production, and 3) reducing nutrient losses to ground and surface waters. After 9 years, soil carbon (C) and soil N remained unchanged or declined slightly in the synthetic fertilizer treatment, but increased with use of compost amendments by 16-27% for C and by 13-16% for N. However, with hairy vetch cover crops, N leaching increased 4 times when compared to clover cover crops. September was the highest month for nitrate leaching, combining high rainfall with a lack of active cash crop or cover crop growth to use residual N. Broiler litter leaf compost (BLLC) showed the lowest nitrate leaching of all the nutrient amendments tested (P= 0.05).