Liquid Hog Manure Application Research Articles

Nitrification inhibitor and management of liquid hog manure: the effect on soil mineral nitrogen dynamics and wheat yield

Management is of fundamental importance in increasing the efficiency of liquid hog manure (LHM) when used as a source of nitrogen (N) and minimizing its impact on the environment. This paper evaluates the effect of surface application and injection of LHM and the use of dicyandiamide (DCD) on the dynamics of mineral N in the soil and on the components of yield in wheat crops. An experiment was conducted at the Federal University of Santa Maria, Frederico Westphalen Campus, Rio Grande do Sul state, Brazil, involving the following treatments: T0 - Control; T1 - surface application of LHM (Sup); T2 - subsurface injection of LHM (Inj); T3 - surface application of LHM + DCD (Sup+DCD); T4 - subsurface injection of LHM + DCD (Inj+DCD), and T5 - application of N, phosphorus (P), and potassium (K) in mineral form (NPK) in 2014 and 2015. The mineral N recovered with the injection of LHM was superior to surface application, and DSD reduced the speed with which anionic forms of mineral N appear. There was a greater increase in the number of ears of wheat with LHM injection. In 2014, the number of grains per ear was higher with the injection of LHM + DCD, whereas in 2015 all the treatments were higher than the control. There was no difference in 1,000-grain weight between treatments with LHM. Hectoliter weight was higher with the injection of LHM + DCD and the yields observed in this treatment were also higher, not differing from mineral fertilization. It is concluded that LHM injection provides lower losses of N and DCD and reduces the speed with which anionic forms of mineral N appear. In addition, the final yield of wheat grains does not differ when comparing LHM + DCD with mineral fertilization.

Impact of liquid hog manure applications on antibiotic resistance genes concentration in soil and drainage water in field crops.

Agricultural practices such as manure applications could contribute to the spread of antibiotic resistance genes (ARGs) within the environment. Our objective was to assess the impact of certain fertilization methods (mineral or manure) and tillage practices (reduced or conventional) on the presence of ARGs and bacteria in soil and drainage water under wheat and grain corn crops. Targeted ARGs tet(T), sul1, and blaCTX-M-1 in liquid hog manure, soil, and water samples were quantified by qPCR. Conventional PCR was used to detect mcr-1 and mcr-2. ARGs in control plots were detected despite the absence of manure, representing an environmental reservoir of resistant microorganisms. The manure application rate higher than 39 m3/ha increased tet(T) and sul1 gene concentrations in soil for more than 180 days. Tillage practices had no impact on ARG concentrations in soil and water samples. The blaCTX-M-1 gene was only detected in seven water samples in 2016, but no link was established with the treatments. The mcr-1 and mcr-2 genes were not detected in all tested samples. This study demonstrated that tet(T) and sul1 gene concentrations increased in soil after liquid hog manure application as well as in drainage water in the next weeks.

Soil mineral nitrogen responses following liquid hog manure application to semiarid forage lands

Bork, E. W., Lambert, B. D., Banerjee, S. and Blonski, L. J. 2013. Soil mineral nitrogen responses following liquid hog manure application to semiarid forage lands. Can. J. Soil Sci. 93: 369–378. Expansion of intensive livestock operations into semiarid regions lacking cultivated lands requires consideration of perennial forages for the efficient and sustainable disposal of manure. Little information exists on the nutrient dynamics associated with the application of manure to these areas. We examined soil mineral nitrogen (N) responses in four sites of the mixed-grass prairie, including two native grasslands and two introduced pastures, following different seasons (fall vs. spring), methods (dribble broadcast vs. coulter injected) and rates of liquid hog manure application (9.4, 18.8, 37.5, 75 and 150 kg ha−1available N). Soil mineral N, including NO3-N, NH4-N and total mineral N, were assessed after application but prior to plant growth in April 1999, and again one growing season later in April 2000. Initial soil N did not vary with season of application. Soil mineral N predictably increased with application rate, but only in the upper soil profile (0–20 cm). Decreases in soil mineral N after one growing season in all treatments highlighted the ability of these perennial forage lands to immobilize large amounts of soil N, a significant portion of which was related to N uptake by vegetation. Compared with broadcast application, manure injection led to 35% greater soil mineral N (both NO3and NH4) prior to plant growth, a response that persisted 1 yr later (+12%), thus demonstrating the N conserved benefits of manure incorporation. Overall, increases in soil mineral N within these forage lands appeared to be relatively short-term in nature, largely depleting over the course of a single growing season, suggesting one-time liquid hog manure application at low to moderate rates may be sustainable in this region of the mixed-grass prairie.

Short-term native grassland compositional responses following liquid hog manure application

Bork, E. W. and Blonski, L. J. 2012. Short-term native grassland compositional responses following liquid hog manure application. Can. J. Plant Sci. 92: 55–65. Intensive livestock operations (ILOs) are becoming more common in remote regions of the Canadian prairies in an effort to reduce conflict with other land uses. This has led to ILOs situated where the typical sink for manure application, cultivated land, is not available, leading to growing interest in using native grasslands for manure disposal. Significant opposition exists to this practice, in part due to limited information available on the impact of manure application to native grassland diversity and species composition. We examined plant species composition changes over two growing seasons following varying rates (∼9.5, 19, 38, 75 and 150 kg ha−1 available N), methods (surface broadcast vs. coulter injected) and timing (fall vs. spring) of one-time liquid hog manure (LHM) application. Our results revealed divergent responses between study sites, with metrics of plant diversity declining in mixed prairie but increasing in fescue grassland with increases in manure application rate. Both communities also demonstrated minor changes in plant species composition, primarily in response to LHM rate and manure application method. Responsive plant species included a mix of native grasses and dicots, some of which may be regarded as undesirable (e.g., Artemisia frigida): however, most vegetation responses were temporary and disappeared by the second year. Although invasion of non-native plant species was not observed, suggesting these communities are tolerant of LHM application, changes in the reproductive effort of dominant grasses (negative in Hesperostipa curtiseta; positive in Pascopyrum smithii and Festuca hallii) suggest LHM application could alter long-term grassland composition. Thus, despite exhibiting resilience to one-time LHM application, future use of native grasslands for manure disposal should be done cautiously.

Utilization of liquid hog manure to fertilize grasslands in southeast Manitoba: impact of application timing and forage harvest strategy on nutrient utilization and accumulation

Liquid hog manure (LHM) is used to improve productivity of grasslands in western Canada. However, application of manure to meet crop N requirements can result in excessive accumulation of P, especially in grazing systems. A three-year study was carried out to assess the impact of timing of liquid hog manure application and harvest strategy on nutrient utilization and accumulation by grasslands in southeast Manitoba. Liquid hog manure was applied annually at a full rate of 142 ± 20 kg available N ha−1 in spring (Single application) or as two half rate applications of 70 ± 6 kg available N ha−1, one in fall and one in spring (Split application). Two harvest strategies, haying and grazing, were employed to export nutrients from grasslands. Spring-applied manure averaged 8.9% dry matter, 5.7 g total N L−1, 1.5 g total P L−1, and 2.1 g total K L−1 and fall-applied manure from the same source averaged 3.9% dry matter, 4.4 g total N L−1, 0.7 g total P L−1, and 2.2 g total K L−1. Manure application based on grass N requirements resulted in at least two times more P and K applied than recommended for Manitoba grasslands. Nutrient (N, P, and K) export from grasslands was five times higher when grass forage was harvested as hay than through grazing. Average nutrient utilization when forage was harvested as hay was 153 kg N ha−1, 18 kg P ha−1, and 123 kg K ha−1 and was higher in the years with increased precipitation. Grazing was not effective in removing nutrients from grasslands as indicated by lower N, P, and K utilization efficiency (% applied nutrient) in grazed (30% for N, 7% for P, and 18% for K) relative to hayed (75% for N 32% for P, and 103% for K) paddocks. Nutrient accumulation was impacted by a combination of harvest strategy and timing of manure application. Both single and split applications increased soil extractable nutrients, but soil extractable nutrients were higher in grazed relative to hayed paddocks following single manure application. After 3 years of manure application, the amount of Olsen-P (62 kg ha−1) exceeded that required for optimal forage growth. However, soil levels did not exceed the soil Olsen-P regulatory threshold (60 mg kg−1) that restricts manure P applications in Manitoba. An analysis of P balance, for this particular soil, indicated that a surplus of 18.9 kg manure P ha−1 (in excess of forage P exported as hay or weight gain) increased the soil Olsen-P concentration by 1 mg kg−1. Nutrient utilization and accumulation will be impacted by timing of manure application and harvest strategy employed as well as amount of precipitation received during the growing season.

Pasture productivity, cattle productivity and metabolic status following fertilization of a grassland with liquid hog manure: A three-year study

Forage yield and quality, cattle and pasture productivity, and enteric methane (CH4) emissions were determined from grass pastures receiving liquid hog manure. Three treatments were evaluated: grass pastures receiving no manure (Control), grass pastures receiving liquid hog manure applied as a single application of 142 ± 20 kg available N ha-1 in the spring (Single) or a split application of 70 ± 6 kg available N ha-1 in both the spring and autumn (Split). Each treatment was represented by two paddocks. The study was carried out over three grazing seasons, from 2004 to 2006, with each grazing season divided into three, 28-d periods. Growing steers (338 ± 32 kg) were introduced into pastures in early summer (May-June) of each year. Standing biomass, measured using quadrats, averaged 1.2, 2.6, and 2.0 ± 0.44 t dry matter (DM) ha-1 for Control, Split and Single pastures, respectively, and was not influenced (P = 0.13) by liquid hog manure application. Liquid hog manure application caused a shift in pasture grasses resulting in a predominance of quackgrass [Elytrigia repens (L.) Nevski]. Nutrient profiles of forage samples collected by hand plucking showed no treatment response for forage gross energy (GE; P = 0.18) and neutral detergent fibre (NDF; P = 0.19), but forage crude protein (CP) (P = 0.027) as well as ash (P = 0.002), K (P = 0.001), P (P = 0.001), and Mg (P = 0.001) concentrations increased with manure application. Liquid hog manure application did not influence dry matter intake (DMI) (P = 0.56), GE intake (P = 0.58), and NDF intake (P = 0.79) of grass forages. Higher CP intake of steers on Split and Single pastures resulted in higher (P = 0.001) serum urea N (5.7 and 5.9 ± 0.42 mmol L-1, respectively) compared with steers grazing Control pastures, 2.5 ± 0.42 mmol L-1. Enteric CH4 emissions (L d-1) tended to be lower (P = 0.09) in cattle grazing the Split pasture treatment. Though application of liquid hog manure did not improve individual animal gains, pasture carrying capacity increased (P = 0.001) from 89 to 324 grazing days ha-1 and liveweight gain increased (P = 0.001) from 100 to 329 kg ha-1 in Control and manured pastures, respectively. Application of liquid hog manure to grasslands generated significant benefits through improved forage quality and pasture productivity measured as carrying capacity and liveweight gain. Split liquid hog manure application may have a further benefit in terms of improved carrying capacity and lower enteric CH4 emissions. Key words: Liquid hog manure, enteric methane, beef cattle, carrying capacity, serum urea nitrogen

Estimation of carbon dioxide production and energy expenditure of grazing cattle by the sulphur hexafluoride (SF6) tracer gas technique

The purpose of the study was to explore the suitability of the sulphur hexafluoride (SF6) tracer gas technique to estimate CO2 production and energy expenditure (EE) for grazing animals on pastures typical of western Canada. During each year of a 3-yr study, CO2 emissions were collected from 60 yearling steers on grass pastures receiving one of three fertility treatments: no manure, liquid hog manure applied as a split application (74 kg available N ha-1) in the spring and fall, and a single application of liquid hog manure applied at a rate of 155 kg available N ha-1 each spring. The mean CO2 production estimate across all treatments was 5424 ± 2218 L d-1 (mean ± SD) with a range of 1099 to 11548 L d-1. When compared across three grazing periods in June, July and August, steers produced more (P < 0.05) CO2 in June than in either July or August. Metabolic body weight (BW0.75), average daily gain (ADG), standing forage biomass, and forage neutral detergent fibre (NDF) and crude protein (CP) contents explained 33% of the variation in CO2 production. Energy expenditure (EE) was estimated from CO2 production by adopting an energetic equivalent of 22 kJ L-1 CO2 and EE was calculated for animals that were not losing body weight at time of measurement. The average EE estimate was 1.2 ± 0.5 MJ kg-1 BW0.75 d-1 with a range of 0.2 to 2.8 MJ kg-1 BW0.75 d-1. Energy expenditure declined as ADG and forage biomass declined, but EE was not influenced (P > 0.05) by fertility treatment. The EE estimate was higher (P < 0.05) early in the grazing season (June) and declined as the grazing season progressed. The SF6 tracer gas technique was able to estimate EE of individual animals without interfering with herd dynamics. The technique was also able to show differences in EE in response to pasture conditions. The results of this study suggest that the SF6 tracer gas technique shows potential as a simple and non-invasive method of estimating CO2 production and EE for grazing animals. Further validation under different grazing conditions and with animals undertaking different degrees of activity is required. Comparisons with other field techniques of estimating EE are also important. Key words: Energy expenditure, carbon dioxide, sulphur hexafluoride, grazing animals

Evaluating phosphorus loading from repeated manure applications to two Saskatchewansoils

An understanding of the impact of repeated manure additions on soil phosphorus (P) is needed to determine appropriate manure application rates for prairie soils and manure sources. The objective of this study was to assess the loading of manure-derived phosphorus using P budgets and soil P measurement techniques applied to two Saskatchewan soils with known histories of manure application. Liquid hog manure (LHM) and solid cattle manure (SCM) treatments were applied annually over 8 yr to Black Chernozemic soils (Dixon site), and LHM was applied to Dark Brown Chernozemic soils (Plenty site) over 6 yr. Soil samples were collected in the spring of 2003 and 2004 and analyzed for labile P (Modified Kelowna extractable, Olsen extractable, water extractable, and Plant Root Simulator exchange resin methods) and total P. The P budgets were in good agreement with the observed patterns in labile soil P at the two sites. The annual application of LHM (37000 L ha-1 yr-1) at agronomic nitrogen (N) rates with no additional P fertilizer (Dixon only) did not significantly elevate soil labile P compared with the unfertilized controls at both Dixon and Plenty. The annual application of SCM (7.6 Mg ha-1 yr-1) at agronomic N rates did not significantly elevate soil labile P compared with the unfertilized control at Dixon; whereas of SCM at higher rates (15.2 Mg ha-1 yr-1 and 30.4 Mg ha-1 yr-1) showed some elevation in labile soil P. Measures of labile P were sensitive to P surpluses or deficits predicted by P balances, and all methods of measuring labile soil P were strongly correlated with one another at both sites (r ≥ 0.803 at P ≤ 0.01). Key words: Manure, cattle manure, nitrogen, phosphorus, soil test phosphorus

Ammonia and nitrous oxide emissions from two acidic soils of Nova Scotia fertilised with liquid hog manure mixed with or without dicyandiamide

Gaseous nitrogen (N) loss from field-applied manure in the form of ammonia (NH 3) and nitrous oxide (N 2O) has negative agronomic, environmental and health implications. This study was undertaken to evaluate the combined effect of soil type and dicyandiamide (DCD) on NH 3 and N 2O emissions following application of liquid hog manure. Soil samples (100 g) were placed in 500 mL screw-top Mason-jars and de-ionised water was added to bring the soil samples to 50%, 70% and 90% water-filled pore space (WFPS). Slurry and slurry + DCD treatments were applied at a rate of 116 000 l ha −1. The jars were then sealed and incubated at 21 °C for 21 d. Ammonia volatilisation was quantified using boric acid traps while N 2O gas concentrations were analysed using gas chromatography. Results showed that DCD had no effect ( p > 0.05) on either NH 3 or N 2O emissions. However, soil type had a significant effect ( p < 0.05) on both gases. Overall, the Pugwash soil produced 3 and 2.5 times more NH 3 and N 2O, respectively, than the Acadia soil. N 2O emissions from both soils increased with an increase in %WFPS, indicating that during the spring and fall in Atlantic Canada, when soils are generally wet, a significant amount of N 2O may be emitted from these soils. The relationship between cumulative N 2O and %WFPS was best described by an exponential function R 2 = 0.83 and p < 0.05 (both soils). Therefore, soil type should be taken into consideration when formulating N 2O emission factors. The addition of DCD together with slurry may not be a viable strategy to mitigate N 2O emissions from acidic soils. To reduce emissions of both gases, livestock slurry should not be applied on wet soils.

Effect of lime, dicyandiamide and soil water content on ammonia and nitrous oxide emissions following application of liquid hog manure to a marshland soil

The loss of nitrogen (N) from field-applied animal manure through ammonia (NH3) volatilisation and nitrous oxide (N2O) emission is of major environmental concern. Both lime and dicyandiamide (DCD) have been suggested as amendments that can mitigate N2O emissions, but simultaneously increase the risk of NH3 volatilisation. This study evaluated the impact of lime and DCD on NH3 and N2O emissions following application of liquid hog manure. Hydrated lime (Ca(OH)2) was added to an acidic soil to achieve three pH levels (4.7, 6.3 and 7.4). Soil samples (100 g) were then placed in 500 ml screw-top Mason-jars and de-ionised water was added to bring the samples to 50, 70 and 90% water-filled pore space (WFPS). Slurry was applied at a rate equivalent to 116,000 l ha−1, while DCD was applied at 30% of the NH4-N rate applied. Jars were sealed and incubated at 21°C for 21 d. Ammonia volatilisation was quantified using boric acid traps, while N2O gas concentration was analysed using gas chromatography. Dicyandiamide had no effect (P>0.05) on either NH3 or N2O emissions. Both NH3 and N2O emissions increased (P<0.05) as WFPS increased, with emissions ranging from 0.9 to 1.4 kg NH3-N ha−1 and 123 to 353 g N2O-N ha−1, respectively. Liming decreased (P<0.01) N2O emissions from 547 to 46 g N2O-N ha−1, but increased (p<0.01) NH3 volatilisation from 0.36 to 1.92 kg NH3-N ha−1. Results suggest that liming to a pH ≥6.3 can reduce N2O emissions, however, this reduction will be accompanied by a substantial loss of NH3.

Effect of Manure on Glyphosate and Trifluralin Mineralization in Soil

Manure additions to soil may alter soil chemical, physical, and biological characteristics, and thereby change pesticide fate processes in soil. This is the first study to examine the impact of liquid hog manure amendments on glyphosate and trifluralin mineralization in soil. Experiments were conducted in soil microcosms in the laboratory for a total of 332 (glyphosate) and 430 (trifluralin) days. The rate and amount of mineralization of both glyphosate and trifluralin were significantly influenced by the additions of fresh manure to soil in the laboratory and by the history of manure applications in the field. However, the maximum difference in herbicide mineralization between soils that were free of manure application and those amended with manure in the field or in the laboratory was only 6.1% and 7.3% of that initially applied, for trifluralin and glyphosate, respectively. Therefore, we conclude that liquid hog manure application to soil will have no significant effect on the mineralization of glyphosate and trifluralin under field conditions.

Persistence of Escherichia coli and Salmonella in Surface Soil following Application of Liquid Hog Manure for Production of Pickling Cucumbers

Liquid hog manure is routinely applied to farm land as a crop fertilizer. However, this practice raises food safety concerns, especially when manure is used on fruit and vegetable crops. The objectives of this project were to evaluate the persistence of Escherichia coli and Salmonella in surface soil after application of liquid hog manure to fields where pickling cucumbers were grown and to verify the microbiological quality of harvested cucumbers. Mineral fertilizers were replaced by liquid hog manure at various ratios in the production of pickling cucumbers in a 3-year field study. The experimental design was a randomized complete block comprising four replicates in sandy loam (years 1, 2, and 3) and loamy sand (year 3). Soil samples were taken at a depth of 20 cm every 2 weeks after June application of organic and inorganic fertilizers. Vegetable samples were also taken at harvest time. Liquid hog manure, soil, and vegetable (washed and unwashed) samples were analyzed for the presence of Salmonella and E. coli. An exponential decrease of E. coli populations was observed in surface soil after the application of manure. The estimated average time required to reach undetectable concentrations of E. coli in sandy loam varied from 56 to 70 days, whereas the absence of E. coli was estimated at 77 days in loamy sand. The maximal Salmonella persistence in soil was 54 days. E. coli and Salmonella were not detected in any vegetable samples.

Herbage yield and crude protein concentration of rangeland and pasture following hog manure application in southeastern Alberta

Intensive hog production is expanding into semi-arid regions of Alberta, where perennial forage lands are increasingly targeted for manure applicati on despite limited guidelines for its efficient use. Herbage yield and crude protein were assessed over two consecutive years within two native rangelands and two tame pastures, following different rates (10, 20, 40, 80 and 160 kg ha-1 NH4-N), methods (surface banding vs. subsurface injection) and seasons (fall vs. spring) of one-time liquid hog manure (LHM) application. Increasing manure rates improved grass yield across all sites the first growing season after treatment, from 1626 to 3576 kg ha-1. Although absolute increases in production were greatest on tame pasture, relative yield increases were similar among sites. Average crude protein (CP) concentration also increased from 69 to 91 g kg-1 in the first year. Despite low rainfall and the absence of a yield response in the second year, grass CP and crude protein yield (CPY) were maximized with increased manure application, highlighting the positive effects of manure on forage production, even with drought. Forb yields demonstrated variable effects among sites, with increasing manure decreasing alfalfa and increasing native forbs. Overall, both semi-arid tame pastures and native rangelands responded positively to LHM application, highlighting the complementary nature of hog and forage production under these conditions. Key words: Crude protein yield, forage, hog manure, injection, native rangeland, precipitation

Long-term effects of liquid hog manure on the phosphorus status of a silt loam cropped to corn

Repeated application of animal manure or mineral P fertilizer can significantly increase soil P content and enhance the risk of water contamination. The objectives of this study were to evaluate the long-term (8 yr) effect of liquid hog manure (LHM) applied at high rates and its timing of application on the soil P status and on the risk index of water contamination by P. Spring (S), fall (F), or spring + fall (SF) applications of LHM on a silt loam (Humo Ferric Podzol) were compared to recommended application rates of mineral fertilizer (MF) in a continuous corn (Zea mays L.) system. Total P applied ranged from 7 to 34 kg P ha-1 yr-1 in the MF treatment and from 106 to 150 kg P haP ha-1 yr-1 in the LHM treatments. Soil samples were collected to 1.0-m depth after one, six and eight annual applications. Applying high rates of LHM for 8 consecutive years resulted in a significant (P ≤ 0.10) enrichment in total soil P content relative to MF at the 0- to 20-cm soil depth. The effects of LHM on labile P forms (water soluble P, Pw and Mehlich-III extractable P, M3P) were also restricted to the 0- to 20-cm depth with values as high as 11 mg kg-1 for Pw and 241 mg kg-1 for M3P in the LHM plots. The degree of soil P saturation, evaluated as Pox/(Alox+Feox), increased to 15% in the 0- to 20-cm depth after 6 to 8 yr of LHM application. Saturation values of 12 to 15% were also found at the 80- to 100-cm depth in some LHM plots. The P index rating was always medium (109 to 216) in soil receiving MF but was high (217 to 432) after 6 to 8 yr of heavy LHM applications, which indicates a high potential risk of soil P transfer to surface water. The results of this study showed that timing of application had little influence on long-term soil P status. Overall, applying LHM at high rates greatly increased total soil P, the degree of soil P saturation, and the labile P forms in the surface horizons but had little effects below 20 cm. Key words: Hog manure, soil P, long-term effects, labile P, P saturation

Soil microbial biomass and enzyme activity following liquid hog manure application in a long-term field trial

Liquid hog manure (LHM) addition to soils in corn silage (Zea mays L.) production may benefit microbial activity by providing C and other nutrients. The objective of this study was to compare the effects of a LHM application to that of inorganic fertilizers (IF) on the biological activity of a Le Bras silt loam soil (Humic Gleysol) under continuous corn production and LHM fertilization. Amounts of 0 to 120 m3 LHM ha−1 and 150 N–150 P2O5–150 K2O kg ha−1 were applied to silage corn. The 0- to 15-cm and 15- to 30-cm soil layers were sampled 28 d after the 18th yearly LHM application. The LHM inputs, particularly at 90 m3 ha−1, resulted in higher enzyme activities and microbial biomass C (MBC) than IF or the unamended control in the 0- to 15-cm soil layer. The 90 m3 LHM ha−1 also gave higher microbial biomass N (MBN) than IF in this soil layer. Application of LHM had no effect on the activities of the enzymes studied or on the MBC and MBN contents in the 15- to 30-cm layer. Ammonifier population was highest with 60 m3 LHM ha−1 in both soil layers. Nitrifier population was not affected by LHM in the top soil layer, but was linearly increased by LHM rates in the 15- to 30-cm layer. This study showed that LHM addition may enhance enzyme activities, microbial biomass and the N mineralizer population in the plow layer of a soil in a corn silage monoculture. Key words: Corn, pig slurry, microbial biomass, monoculture, soil enzyme

CHEMICAL AND SPECTROSCOPIC CHARACTERIZATION OF COLLOIDAL FRACTIONS SEPARATED FROM LIQUID HOG MANURES

Direct-land application of liquid hog manure is the most common practice for recycling this type of waste. However, liquid hog manure not only contains valuable agronomic substances, it also includes substances that may pose serious environmental concerns. Pyrolysis-Field Ionization Mass Spectrometry(Py-FIMS), 13C Nuclear Magnetic Resonance (13C NMR), and Fourier-Transform Infra-Red (FTIR) were spectroscopy methods used to characterize colloidal fractions separated from three liquid hog manures. The spectroscopic data revealed that the colloids in the liquid manures contain relatively high concentrations of sterols(between 10.1 and 12.7% of Total Ion Intensity (TII)), which may have originated from animals and plants as well as from fortified feeds. Other significant colloid components, as percentages of TII, are lipids (5.3 to 11.9%), free fatty acids (3.4 to 9.5%), carbohydrates (2.5 to 6.0%), peptides (3.5 to 4.9%), n-alkylaromatics (2.9 to 4.0% C), N-compounds (3.1 to 4.7%), and phenols (2.5 to 4.0%). The presence of relatively high concentrations of sterols and phenols indicate that liquid hog manure has a high propensity for contributing to the contamination of soils and surface and subsurface waters.