Heidi M. Waldrip

Characterization of organic matter in beef feedyard manure by ultraviolet-visible and fourier transform infrared spectroscopies.

Manure from beef cattle feedyards is a valuable source of nutrients and assists with maintaining soil quality. However, humification and decomposition processes occurring during feedyard manures on-farm life cycle influence the forms, concentrations, and availability of carbon (C) and nutrients such as nitrogen (N) and phosphorus (P). Improved understanding of manure organic matter (OM) chemistry will provide better estimates of potential fertilizer value of manure from different feedyard sources (e.g., manure accumulated in pens, stockpiled manure after pen scraping) and in settling basin and retention pond sediments. This will also assist with identifying factors related to nutrient loss and environmental degradation via volatilization of ammonia and nitrous oxide and nitrate leaching. We used Fourier-transform infrared (FTIR) and ultraviolet-visible (UV-vis) spectroscopies to characterize structural and functional properties of OM and water-extractable OM (WEOM) from different sources (surface manure, manure pack, settling basin, retention pond) on a typical commercial beef feedyard in the Texas Panhandle. Results showed that as beef manure completes its on-farm life cycle, concentrations of dissolved organic C and N decrease up to 98 and 95%, respectively. The UV-vis analysis of WEOM indicated large differences in molecular weight, lignin content, and proportion of humified OM between manures from different sources. The FTIR spectra of OM and WEOM indicate preferential decomposition of fats, lipids, and proteins over aromatic polysaccharides such as lignin. Further work is warranted to evaluate how application of feedyard manure from different sources influences soil metabolic functioning and fertility.

Analysis of Carbon Functional Groups in Mobile Humic Acid and Recalcitrant Calcium Humate Extracted from Eight US Soils

Abstract Solid state 13 C nuclear magnetic resonance (NMR) spectroscopy is a common tool to study the structure of soil humic fractions; however, knowledge regarding carbon structural relationships in humic fractions is limited. In this study, mobile humic acid (MHA) and recalcitrant calcium humate (CaHA) fractions were extracted from eight soils collected from six US states and representing a variety of soils and ecoregions, characterized by this spectroscopic technique and analyzed for statistical significance at P = 0.05. We found that the abundances of COO and N-C=O functional groups in the MHA fractions were negatively correlated to soil sand content, but were positively correlated to silt, total N and soil organic carbon contents. In contrast, the abundances of the COO and N-C=O functional groups were only positively correlated to the content of clay in the CaHA fractions, indicating that the two humic fractions were associated with different soil components. The two 13 C NMR peaks representing alkyls and OCH 3 /NCH were negatively correlated to the peaks representing aromatics, aromatic C-O and N-C=O/COO. Comparison of the sets of data from 13 C NMR spectroscopy and ultrahigh resolution mass spectrometry revealed that the aromatic components identified by the two methods were highly consistent. The comparison further revealed that protein in MHA was associated with, or bound to, the nonpolar alkyl groups, but a component competitively against (or complementary to) aromatic groups in the MHA composition. These observations provided insight on the internal correlations of the functional groups of soil humic fractions.

Arrhenius Equation for Modeling Feedyard Ammonia Emissions Using Temperature and Diet Crude Protein

Temperature controls many processes of NH volatilization. For example, urea hydrolysis is an enzymatically catalyzed reaction described by the Arrhenius equation. Diet crude protein (CP) controls NH emission by affecting N excretion. Our objectives were to use the Arrhenius equation to model NH emissions from beef cattle () feedyards and test predictions against observed emissions. Per capita NH emission rate (PCER), air temperature (), and CP were measured for 2 yr at two Texas Panhandle feedyards. Data were fitted to analogs of the Arrhenius equation: PCER = () and PCER = (,CP). The models were applied at a third feedyard to predict NH emissions and compare predicted to measured emissions. Predicted mean NH emissions were within -9 and 2% of observed emissions for the () and (T,CP) models, respectively. Annual emission factors calculated from models underestimated annual NH emission by 11% [() model] or overestimated emission by 8% [(,CP) model]. When from a regional weather station and three classes of CP drove the models, the () model overpredicted annual NH emission of the low CP class by 14% and underpredicted emissions of the optimum and high CP classes by 1 and 39%, respectively. The (,CP) model underpredicted NH emissions by 15, 4, and 23% for low, optimum, and high CP classes, respectively. Ammonia emission was successfully modeled using only, but including CP improved predictions. The empirical () and (,CP) models can successfully model NH emissions in the Texas Panhandle. Researchers are encouraged to test the models in other regions where high-quality NH emissions data are available.

Applied and Environmental Chemistry of Animal Manure: A Review

Abstract Animal manure consists of predominantly urine and feces, but also may contain bedding materials, dropped feed, scurf, and other farming wastes. Manure is typically applied to soils as fertilizer for agricultural production. The estimated amount of manure produced in 12 major livestock-producing countries is 9 × 109 Mg of manure annually. Manure is rich in plant nutrients. However, manure is also considered as an environmental pollutant when it is over-applied to cropland or following runoff into surface water. Manure can also influence global climate change via emissions of methane (CH4) and nitrous oxide (N2O). Thus, increased and updated knowledge of applied and environmental chemistry of animal manure is needed to shed light on the research and development of animal manure utilization and minimization of its adverse environmental concerns. The advances in basic and applied studies of manure major components, organic matter, phosphorus, and nitrogen, primarily related to US livestock production are summarized in this review. Detailed focus was placed on three notable challenges for future manure research: 1) soil application of animal manure, 2) manure phytate phosphorus, and 3) manure nitrogen availability. This review may contribute to the global effort in sustainable and environmentally sound agriculture by stimulating new ideas and directions in animal manure research, and promoting application of knowledge and insight derived from manure research into improved manure management strategies.

Soil Amino Compound and Carbohydrate Contents Influenced by Organic Amendments

Amino compounds (i.e. amino acids and sugars), and carbohydrates are labile organic components and contribute to the improvement of soil fertility and quality. Animal manure and other organic soil amendments are rich in both amino compounds and carbohydrates, hence organic soil amendments might affect soil processes through these labile components. This chapter first reviews the advances in research on soil concentrations of amino compounds and carbohydrates as impacted by animal manure and other organic amendments. The published papers are mainly on the amino compounds and carbohydrate changes in long-term field trials and laboratory or greenhouse incubations, tracking the fate of amendment-derived amino compounds and carbohydrates in soils. To investigate the amino compound and carbohydrate changes in the short-term (16 weeks), we present a greenhouse pot study (4–16 weeks) which demonstrated that poultry manure increased extractable amino compounds when applied to soil at a high rate, and depressed them at a low application rate. The increase at the high rate was further amplified in rhizospheric soils. Whereas microbial activities promoted carbon (C) and nitrogen (N) mineralization, the presence of ryegrass resulted in lower concentrations of amino compounds and carbohydrates. Finally, we recommend that more types of organic amendments be evaluated for their impacts on soil amino compound and carbohydrate levels, and the relationship in changes between the two types of compounds. Such cumulative knowledge would provide a basis for establishing the specific contributions of amino compounds and carbohydrates to soil N and C dynamics over the course of agricultural seasons and beyond.

Methane Emissions from a Beef Cattle Feedyard during Winter and Summer on the Southern High Plains of Texas

Methane (CH) emissions from enteric fermentation by livestock account for about 2.1% of U.S. greenhouse gas emissions, with beef and dairy cattle being the most significant sources. A better understanding of CH emissions from beef cattle feedyards can help build more accurate emission inventories, improve predictive models, and meet potential regulatory requirements. Our objective was to quantify CH emissions during winter and summer at a typical beef cattle feedyard on the southern High Plains in Texas. Methane emissions were quantified over 32 d in winter and 44 d in summer using open-path lasers and inverse dispersion analysis. Methane per capita emission rate (PCER) ranged from 71 to 118 g animal d in winter and from 70 to 130 g animal d in summer. Mean CH PCER was similar in January, February, and May (average, 85.0 ± 0.95 g animal d) and increased to 93.4 g animal d during the June-July period. This increase coincided with increased dietary fiber. Methane loss ranged from 9.2 to 11.4 g CH kg dry matter intake, with lower values during winter. Gross energy intake (GEI) ranged from 135.2 to 164.5 MJ animal d, and CH energy loss ranged from 4.5 to 4.9 MJ animal d. Fraction of GEI lost as CH (Y) averaged 2.8% in winter, 3.2% in summer, and 3.0% overall. These values confirm the Y value currently recommended by the Intergovernmental Panel on Climate Change for Tier 2 estimates of enteric CH from feedlot fed cattle.

Phosphatase Activities and Their Effects on Phosphorus Availability in Soils Amended with Livestock Manures

The application of livestock manures can impact factors related to phosphorus (P) cycling and concentrations of plant-available P in soils. Specific manure physicochemical properties differ due to livestock species and management practices, which may result in differences in parameters related to soil fertility when manures are applied to soil. To date, no evaluation has been conducted on the differences among manure types on soil phosphatase activities and P availability. This chapter presents information on the most commonly studied soil phosphatases, acid and alkaline phosphomonoesterase and phosphodiesterase, and how manure application influences their activities and P cycling. In a case study, it is shown that soil application of manures from organically managed dairies increases acid phosphatase activity; however, concentrations of available P in soils that receive manure from organic dairies are similar to those that receive manure from conventional dairies. Depending upon specific research goals, different in vitro experimental approaches may be used prior to evaluation of phosphatase activity, but specific methodology influences phosphatase activities and can hinder among-study evaluation of effects of livestock manure on P dynamics. Research avenues are suggested to improve current understanding of the effects of livestock manure on soil quality and functioning related to P availability in soils.

Process-based Modeling of Ammonia Emission from Beef Cattle Feedyards with the Integrated Farm Systems Model

Ammonia (NH) volatilization from manure in beef cattle feedyards results in loss of agronomically important nitrogen (N) and potentially leads to overfertilization and acidification of aquatic and terrestrial ecosystems. In addition, NH is involved in the formation of atmospheric fine particulate matter (PM), which can affect human health. Process-based models have been developed to estimate NH emissions from various livestock production systems; however, little work has been conducted to assess their accuracy for large, open-lot beef cattle feedyards. This work describes the extension of an existing process-based model, the Integrated Farm Systems Model (IFSM), to include simulation of N dynamics in this type of system. To evaluate the model, IFSM-simulated daily per capita NH emission rates were compared with emissions data collected from two commercial feedyards in the Texas High Plains from 2007 to 2009. Model predictions were in good agreement with observations and were sensitive to variations in air temperature and dietary crude protein concentration. Predicted mean daily NH emission rates for the two feedyards had 71 to 81% agreement with observations. In addition, IFSM estimates of annual feedyard emissions were within 11 to 24% of observations, whereas a constant emission factor currently in use by the USEPA underestimated feedyard emissions by as much as 79%. The results from this study indicate that IFSM can quantify average feedyard NH emissions, assist with emissions reporting, provide accurate information for legislators and policymakers, investigate methods to mitigate NH losses, and evaluate the effects of specific management practices on farm nutrient balances.

Nitrous Oxide Emissions from Open-Lot Cattle Feedyards: A Review

Nitrous oxide (NO) emissions from concentrated animal feeding operations, including cattle feedyards, have become an important research topic. However, there are limitations to current measurement techniques, uncertainty in the magnitude of feedyard NO fluxes, and a lack of effective mitigation methods. The objective of this review was to assess NO emission from cattle feedyards, including comparison of measured and modeled emission rates, discussion of measurement methods, and evaluation of mitigation options. Published annual per capita flux rates for beef cattle feedyards and open-lot dairies were highly variable and ranged from 0.002 to 4.3 kg NO animal yr. On an area basis, published emission rates ranged from 0 to 41 mg NO m h. From these studies and Intergovernmental Panel on Climate Change emission factors, calculated daily per capita NO fluxes averaged 18 ± 10 g NO animal d (range, 0.04-67 g NO animal d). This variation was due to inconsistency in measurement techniques as well as irregularity in NO production and emission attributable to management, animal diet, and environmental conditions. Based on this review, it is clear that the magnitude and dynamics of NO emissions from open-lot cattle systems are not well understood. Further research is required to quantify feedyard NO fluxes and develop cost-effective mitigation methods.

Soil Enzyme Activities as Affected by Manure Types, Application Rates, and Management Practices

Manure application can restore soil ecosystem services related to nutrient cycling and soil organic matter (SOM) dynamics through biochemical transformations mediated by soil enzymes. Soil enzymes are crucial in soil metabolic functioning, as they drive the decomposition of organic residues, humification processes, transformations leading to the release of plant available nutrients, stabilization of soil structure, and degradation of xenobiotic (foreign or strange) compounds. However, despite the fact that there is an exhaustive amount of literature available on the effects of manure on soil enzyme activities, there is no comprehensive overview of recent research findings that compares different management scenarios, manure types, and potentially new manure products or management. The purpose of this chapter is to provide a review of the response of enzyme activities to manure applications and their potential implications on soil biogeochemical cycling in agroecosystems. Additionally, this chapter intends to provide some perspective on specific areas where more information is warranted and pinpoint avenues for future research.