Best Management Practices to Improve Environmental Sustainability and Productivity of Grassland Systems Using Hog Manure

Project: MLMMI 03-01-02


  1. Identification of Best Management Practices.
  2. Promotion of Best Management Practices.
  3. Improving economic and environmental sustainability for the livestock sector.

KEYWORDS: nutrient management, greenhouse gas mitigation, persistence of bacteria, water quality


Kim Ominski
University of Manitoba


Status: Completed
Started: 2003-11-01
Completed: 2008-04-03

Funding Partners: who have contributed to MLMMI in support of this project:
Manitoba Pork Council and industry groups - $80,000

Amount Funded: $80,000.00
Performer Funded: $396,540.00
Total Cost: $476,540.00


First Progress Report received on April 1, 2004.
Second Progress Report received on November 1, 2004.
Third Progress Report received on April 1, 2005.
Fourth Progress Report received on November 7, 2005.
Fifth Progress Report received on April 11, 2006.
Final report due November 1, 2006.
Extension granted until March 31, 2007.
Final report received May 8, 2007.
Final revised report received April 3, 2008.


Expansion in the hog sector in Manitoba from less than 2 million head in 1980 to more that 8 million head in 2006 (Knowledge Management, Manitoba Agriculture, Food and Rural Initiatives) has created opportunities for both the beef and dairy cattle industries to improve forage productivity through the application of hog manure. Although the use of hog manure as a fertility source in grassland pasture systems may be mutually beneficial to hog and cattle producers, there are still many aspects of this practice that require further study in the Manitoba production environment including both productivity and environmental sustainability as measured by greenhouse gas production (including enteric methane emissions and soil nitrous oxide/methane emissions), as well as the potential for nutrient accumulation/movement within the soil and movement of pathogens from hog manure to soil, forage and cattle.

To accomplish these objectives, a research/demonstration site was established in September 2003. Treatments examined were i) manure application and ii) method of forage removal. Three strategies for manure application were used: i) no manure ; ii) manure applied as a single application of 110 lbs of available N delivered in the spring; iii) manure applied as a split application with 55 lbs available N applied in the spring and 55 lbs of available N applied in the fall.

Rates of manure application were determined according to guidelines established by Manitoba Agriculture, Food and Rural Initiatives for forage on class 3M land. Targeted rate of application was 110 lbs. available N per acre for Split and Full treatments. Application rates were then determined using the Tri-Provincial Manure Application and Use Guidelines assuming 25% volatilization for surface application of manure and 25% N available from organic N in the first year of application. Manure was agitated for three hours prior to application and throughout the application process, resulting in manure of consistent characteristics. Overall, the solids content of the manure was higher than the average values for liquid pig manure in Manitoba. This relatively high solids content was expected, however, since the manure was pumped out of the primary cell of a three cell manure storage system. The spring manure had a higher solid content than the manure applied in the fall, as well as higher calcium, phosphorus and magnesium content. Phosphorus concentrations in the manure, unlike nitrogen, were highly variable, ranging from 167 to 1672 mg P L-1 manure. The seasonal variability is likely due to the dilution effect from greater water use in barns during the warm summer months as barns are cooled via sprinkler systems and pigs drink more water. In addition, part of the seasonal variation in P concentration may be attributed to differences in the loading periods for the primary cell of the manure storage, where a large portion of the manure solids accumulate. Typically, this earthen manure storage is pumped out onto perennial forage fields in the summer. Therefore, the amount of dry matter which accumulates in the primary cell of the manure storage is typically higher in the spring as the period for loading manure into the storage is longer compared to the relatively short loading period for the material pumped in the fall. As a consequence of the higher dry matter content and associated levels of nutrients, the rates of manure application for this study were lower than those for manure with more typical nutrient concentrations. In addition to the observed seasonal variability in P, there was also variation between years. The very low concentrations of all nutrients and dry matter in the fall of 2004 may be attributed to unusually high rainfall and cool temperatures, resulting in low evaporation losses.

Soil nutrient profiles were examined prior to manure application and in the fall of each study year (prior to the Split manure application) to determine if elements in the applied manure moved through the profile towards groundwater. The elements of interest included available nutrients, nitrogen and phosphorus, as well as chloride. Nutrient profiles in soil up to 120 cm did not show an accumulation of available nitrogen or phosphorus with manure application. Chloride, which served as a marker to determine if nitrate leaching occurred, tended to be highly variable under manured plots. An increase in Cl- concentration at 60-90 and 90-120 cm depths for replicate 1 of the Control-hayed and replicate 2 of the Control-grazed plots occurred following the very dry summer and fall of 2006. The source of this Cl- is unknown. Although potential sources of chloride from adjacent plots or groundwater may be speculated, future studies using a tracer which is not present in soil or groundwater and not removed by plants or adsorbed to soil (ex. bromide) are required.

Detailed sampling and analysis of plant available nitrogen and phosphorus clearly showed an increase in phosphorus in the near soil surface (0-5 cm) of manure-treated soil (>44 ppm Olsen-P compared to <12 ppm in Control treatments). The rate of increase of available phosphorus in soil was estimated by extrapolating the rate of P increase measured from 2004 to 2006. These projections indicated soil test P levels will increase exponentially rather than linearly with continued application of manure. Based on these estimates, it is possible that by the year 2010, manure application will be required to shift to a rate of manure application equivalent to 2X P removal from the hay and grazed treatments. It is important to note that these projections are based on a relatively small data set. In contrast to available P, available nitrogen (ammonium and nitrate) did not increase in the near soil surface layer.

The influence of cattle on nutrient distribution near watering and mineral supplement sites was also examined. Surface soil nutrient concentrations were much greater for bare earth areas (area of high animal traffic around waterers and supplements) compared to grassed areas in 2005 and in 2006. Phosphorus, nitrate and chloride were all very high in the bare earth areas. In 2006, more detailed sampling and analysis was conducted. Phosphorus levels were highest in the 0–5 cm depth of the bare earth zone. The results indicate that urine and dung deposition in high traffic areas can create areas within grazed land that have extremely high nutrient levels. Movement of waterers and mineral supplement to a new location is advised to prevent the establishment of nutrient accumulation in bare earth areas.

Application of hog manure on hayfields increased forage yield relative to hayfields receiving no fertility. Average standing forage biomass generated in Control, Split and Full hayfields were 2.9, 7.0 and 6.7 ± 0.21 t ha-1, respectively. In addition to increased yield, nutrient profile of the forage was also significantly improved. Mean standing forage crude protein (CP) was lowest in unmanured standing forage (7.5 ± 0.26 % CP), while Split and Full hayfields had CP concentrations of 10.2 and 11.0%, respectively. Neutral detergent fibre was higher in Split hayfields (61.8 ± 1.05 %) than in Control (57.3%) but not different than Full (59.6%) due to its advanced state of maturity at cutting. Gross energy was highest in manured hayfields (18.3, 18.7 and 18.6 ± 0.06 kJ g-1 DM, in Control, Split and Full hayfields, respectively.

Application of hog manure also increased nutrient profile of pasture forages relative to those receiving no fertility. Mean forage CP was almost doubled with manure application. Serum urea nitrogen was measured in the grazing cattle to determine overall protein status of the animals. Steers grazing unmanured pastures had lower serum urea N values compared to steers grazing manured pastures. Animal intake and enteric methane emissions (% GEI) were unaltered by the changes in forage quality as a result of manure application. Previous research has indicated that CH4 production is influenced by the availability and quality of the forage being consumed. In this study, pasture forage availability was never limiting and was adequate for selective grazing, a behaviour in which cattle often select forages that have higher levels of CP and lower levels of ADF than is available in the average of the pasture forages present.

The addition of hog manure increased pasture carrying capacity over the grazing season by more than three-fold compared to unmanured pastures, which averaged 89 grazing days ha-1 yr-1. Animal productivity increased from 100 kg gain ha-1 for unfertilized to 319 and 339 kg gain ha-1 for Split and Full pasture treatments, respectively.

Nitrogen and phosphorus (P) removal efficiencies based on nutrients applied were significantly greater in the hayed system compared to the pastoral system, in which only 4.9 % of applied N and 5.0 % of the applied P were removed. The low nutrient utilization efficiencies in each system indicate a need to monitor the rate or frequency of liquid hog manure application to reduce nutrient build-up in the grassland system.

Greenhouse gas emissions as affected by manure application and timing were also measured from soil. In 2004, methane (CH4) in soil was produce for several weeks following spring application of manure in areas of the plots saturated with water. In contrast, methane production in 2005 occurred mid-season following a period of high rainfall and was not associated with manure application. We speculate that the vigorous plant growth in manured plots and drop in water table height resulting in release of water-trapped methane to the atmosphere. In contrast, 2006 was a very dry year. Methane was not emitted but rather consumed under the predominantly aerobic soil conditions. Nitrous oxide (N2O) was emitted for several weeks following spring application of manure and was no longer apparent by summer in each year. Nitrous oxide from soil was clearly the most important of the greenhouse gases produced in 2004 and 2006 while methane predominated in 2005, a year which was characterized by increased precipitation.

Over the three study years, average net N2O and CH4 emissions, expressed as kg CO2 equivalent ha-1 , increased from 63 for the Control treatment to 196 and 250 for the Split and Full hayed treatments, respectively. However, net N2O and CH4 emissions were unaffected by manure treatment when expressed as kg CO2 equivalent kg-1 live weight gain ha-1 over the study period (0.633 Control, 0.613 Split and 0.738 Full kg CO2 eq. kg-1 live weight gain ha-1).

The dramatic increase in above ground productivity prompted an examination of the impact of manure application on root productivity. Root mass C in the 0-5 cm depth was 2,695 and 3,588 kg C ha-1 for the Control- and Full-hayed plots in replicate 1 (Figure 19). As such, manure application resulted in 900 kg C ha-1 or about 3,300 CO2 eq. ha-1; a value significantly higher than the 897 CO2 eq. ha-1 associated with emissions of CH4 from soil, direct N2O emission from soil and indirect emission of N2O from volatilization of ammonia in the Full-hayed plots

Presence of Salmonella, Yersina and E. coli were examined using both standard culture and DNA techniques. Salmonella and E. coli were present in hog manure at the time of application to the experimental plots during both years studied. Yersinia enterocolitica was not detected in hog manure at anytime during the study. Salmonella and E. coli were detected on forage two days after manure application but were not detected on forage before cattle were grazed. Salmonella was not detected in soil at any time before or after manure application during both years of the study. During this study, Salmonella and E. coli present in hog manure did not appear to have been transferred to cattle grazing manure-treated fields. Low numbers of E. coli and Salmonella on vegetation and in soil at the time cattle started to graze may have been the main reason cattle did not acquire organisms from the applied hog manure. E. coli was detected in one background well as well, as in two wells on the experimental site, before manure application in 2005, suggesting that the source of contamination might be not be linked to experimental tests conducted. Salmonella was detected in four wells 20 days after manure application in the fall of 2005. Salmonella serovars recovered from these wells could not be traced back to serovars isolated from hog manure.

Research data gathered from this site has resulted in the submission of three scientific publications, with five others in preparation. The site has also served as an excellent location for student training at both the graduate and undergraduate level. Two students have successfully completed graduate programs with data collected from the site while three more students are in the process of completing their postgraduate degrees. Finally, the site has served as an excellent means of communicating information regarding productivity and environmental sustainability of grassland systems to the agricultural sector and the community at large.



PowerPoint presentation of data - September 6, 2007
Final Report - written document

Manitoba Pork represents 613 Manitoba hog farms