Environment

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Prairie Swine Centre is an affiliate of the University of Saskatchewan


Prairie Swine Centre is grateful for the assistance of the George Morris Centre in developing the economics portion of Pork Insight.

Financial support for the Enterprise Model Project and Pork Insight has been provided by:



Author(s): Steve Sager and David Przednowek
Publication Date: January 1, 2005
Country: Canada

Summary:

Manitoba has experienced dramatic growth in the hog industry. Hog production is also expanding from traditional grain-producing areas of the province into areas primarily involved in forage and cattle production, such as southeastern Manitoba and the Interlake. Some of the forage land that is currently used or destined for receiving hog manure in the future is considered sandy or coarse-textured soil. Such soils tend to have a higher risk of leaching of nutrients than finer textured soils. Currently, there is limited information regarding the agronomic and environmental impacts of the application of hog manure to forages grown on coarse-textured soils. Studies were initiated near Zhoda, MB, to determine the impact of the timing and rate of hog manure applied to forage grown on coarse textured soils with high water tables. Precipitation and soil groundwater data were also collected. In Experiment 1, manure treatments equivalent to 0, 60, 90, 120 pounds of nitrogen per acre were applied in the summer of 2002 in summer and fall after forage harvesting; a treatment consisting of a split application of manure equivalent to 120 pounds of nitrogen per acre was also applied (60 pounds per acre each in summer and fall). Four replicates were arranged in a completely randomized design. In Experiment 2, manure was applied at rates equivalent to 0, 100, 200, 300, and 400 pounds of nitrogen per acre in spring 2004 in three replicates in a strip plot design. Besides forage yield and quality, the distribution of nitrate- N and phosphorous in the soil profile was also monitored in both experiments. In Experiment 1, evidence of nutrient leaching downward in the soil profile was minimal. Depending on conditions during the growing season and subsequent to manure application, N losses may have accounted for a considerable share of the N that was initially applied. Given the poor soil fertility at the site, strong yield response to applied manure was also likely a contributing factor to minimizing nutrient leaching. The evidence suggests that forages indeed are a strong candidate for manure application, especially in circumstances where inherent soil fertility is poor. Evidence of nutrient leaching was more compelling in Experiment 2. There was strong evidence of nutrient leaching downward in the soil profile for the 300N and 400N treatments. At the last sampling date, there was considerably more nitrate-N at depth in the soil profile for the 400N treatment compared to the other treatments applied. In both experiments, residual soil nutrient levels were low to very low, although there was evidence of potassium accumulation in both experiments as manure application rate increased. Residual soil N levels met the regulations set out by the Manitoba Manure and Mortalities Management Regulations, and were low to very low for nitrogen, phosphorous, and potassium basis the Manitoba Soil Fertility Guide. However, the evidence of nutrient leaching in Experiment 2 during the growing season indicates a real threat of downward movement of nitrate-N where application rates are excessive relative to crop demand. Forages responded strongly to manure application with respect to nutrient uptake, nutrient content, and dry matter yield. In Experiment 1, dry matter yields increased considerably as manure application rate increased, as did nutrient uptake. The impact on forage nutrient content was less consistent across harvests, although as expected there was a trend in most instances of increasing nutrient content with increasing manure application rate. Fall-applied manure appeared to produce higher forage yields, possibly as a result of greater nutrient losses in summer-applied treatments as well as the lack of nutrient response when dry conditions prevailed during the summer period. Split N application was no more effective at increasing forage productivity than the 120N treatment when considering productivity over a production cycle (i.e. fall and summer harvest). Tming of nutrient availability is a key consideration in attempting to maximize forage productivity. In Experiment 2, for example, it was clear that nutrient availability was delayed somewhat relative to application date, as indicated by a delay in the accumulation of nitrate-N in the upper soil profile. Given the lack of leaching observed in Experiment 1 (up to target N rate of 120 lb ac-1), increasing manure application rates may be feasible relative to current recommendations. Splitting manure application rates may also provide another means of increasing manure application rates without causing adverse effects to the environment.

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