Project: MLMMI 00-01-05
Objective
To determine the difference in runoff water quality leaving agricultural fields treated with manure relative to those treated with commercial fertilizers.
Performer
Bill Turner, Deerwood Soil and Water Management Assoc. Ph. (204) 822-7273
Details
Status: Completed
Started: 2000-03-28
Completed: 2002-10-02
Funding Partners: who have contributed to MLMMI in support of this project:
ARDI - $9,000
Manitoba Pork Council and industry groups - $9,000
Amount Funded: $18,000.00
Performer Funded: $43,000.00
Total Cost: $61,000.00
Activity
First Interim Report received Oct 6/00.
Second report received Apr 9/01.
Final report due September 28, 2001; received October 2, 2002.
Summary
A study was conducted in the South Tobacco Creek Watershed from 1998 to 2001 to compare surface water quality runoff characteristics between fields amended with inorganic commercial fertilizer and organic (hog manure) fertilizer. Water runoff samples were also collected from a forage field and a relatively undisturbed natural wooded area. The study was conducted with the collaboration of producers within the watershed and various agencies that included Manitoba Conservation , Environment Canada, Manitoba Agriculture and Food, Prairie Farm Rehabilitation Administration, Manitoba Pork Est , the Manitoba Livestock Manure Management Initiative and the Agricultural Research and Development Initiative.
There was no indication that application of hog manure onto land during the fall by broadcast spreading and incorporation into the soil within 48 - 72 hours caused greater fecal coliform values in spring runoff than from locations without manure applications. Mean fecal coliform bacteria values from the field applied with hog manure were within ranges from the Forage Field, the Natural Wooded Area, and fields in the Twin Watershed that did not receive manure.
Concentrations of nutrients and organic carbon were significantly higher in runoff from the Manured Watershed field than the other study field sites when an appreciable amount of runoff (481 m3 ha-1) occurred from this site during 1998. In 1998, mean total nitrogen and phosphorus concentrations were 18.4 mg L-1 and 2.3 mg L-1, respectively. Meanwhile, concentrations of nitrogen and phosphorus from the Natural Wooded Area, Forage Field, Zero-till field and Conventional-till field ranged from approximately 0.4 - 2.9 mg L-1 and < 0.1 - 0.54 mg L-1, respectively. The relatively substantive runoff volume during 1998 also coincided with a relatively high areal loss (kg ha-1) of nutrients from the Manured Watershed field compared to the Conventional-till and Zero-till fields. Total nitrogen loss from the Manured Watershed field was approximately 8.63 kg ha-1 compared to between only 1.72 - 1.77 kg ha-1 from the Zero-till and Conventional-till fields, despite the Manured Watershed field being only about one quarter the size of the other fields. Higher nutrient losses from the Manured Watershed field in 1998 were considered due to much higher nutrient values in the upper 15 cm of soil of the Manured Watershed than the other fields.
Nutrient loss from the Manured Watershed field was much lower than from the Conventional-till or Zero-till fields between 1999 - 2001 even though nutrient values in soil were usually above agronomic rates and continued to be higher than the Zero-till or Conventional-till fields during spring runoff. Total nitrogen loss from the Manured Watershed field was < 0.1 kg ha-1 compared to between 0.81 - 3.67 kg ha-1 from the Conventional-till and Zero-till fields. The main reason for this situation was due to poor runoff from this field in those years. Runoff from the Manured Watershed field was not measurable in 2000 and only ranged between 2% - 6 % of the 1998 value during 1999 and 2001. This condition greatly reduced the opportunity for nutrient loss in surface runoff.
The mean total nitrogen concentration from the Conventional-till field during spring runoff 1999 was 16.4 mg L-1 and was the second highest value observed during this study. The occurrence of this concentration was attributed to the addition of anhydrous ammonia-N during the previous fall of 1998. Although anhydrous ammonia-N was also applied to the Conventional-till field in the fall of 1999 at the same application rate as 1998, the absence of runoff from the Conventional-till field during 2000 prevented a repeated occurrence of relatively high nitrogen concentrations in spring runoff.
Mean total phosphorus concentrations in runoff from the fields were usually < 2 mg L-1, except for the Manured Watershed and Zero-till fields during 1998 and 2001, respectively. During these years, mean total phosphorus values from the Manured Watershed and Zero-till fields were approximately 2.3 mg L-1 and 2.7 mg L-1, respectively. Mean phosphorus concentrations from the Forage Field and Zero-till field appeared to be slightly increasing each successive year and this was thought to be likely due to increased organic build up on the soil surface over time. The dissolved form of phosphorus as well as the dissolved forms of nitrogen and organic carbon comprised the major portion the total concentrations for each variable.
Mean suspended solid concentrations were consistently higher from the Conventional-till field than other field sites. This was considered due to more surface soil exposure and less organic matter on the soil surface to help reduce soil and other fine particulate matter transport.
The total nutrient losses from fields were usually lower from precipitation events in the post-spring runoff period than during spring mainly because there were more days with runoff in spring to provide more volume.
The nutrient content of hog manure from a single operation was not consistent between years. Nitrogen content varied more than phosphorus. Nitrogen was fairly consistent for samples from the first two years of the study and a sample collected a couple of years prior to the study, and was less consistent for the later two years of study. This variation affects estimates for determining fertilization rates and emphasizes the importance for soil testing areas receiving hog manure, especially on land that receives repeated annual applications.
Total phosphorus values in soil samples collected from the Manured Watershed field during fall showed a consistent, slightly increasing trend with consecutive annual applications of hog manure over a four-year period. This was attributed to application rates based upon N requirements and more P than needed for crops was incidentally added while meeting nitrogen requirements.