DOT Project Number:  90-00-LRTF-801, 912

Fiscal Year:  1998-1999

Award:  $27,000.00

Principal Investigator:  Trelan Wilson, sprairie@mailrelay.dwx.com

Summary Report:

MOWING AND BURNING STRATEGIES TO CONTROL WEEDS IN RECONSTRUCTED PRAIRIES

Key to the four graphs below:

High P = Soil phosphorus greater than or equal to 19 parts per million
Low P = Soil phosphorus less than 15 parts per million

Control = No treatment
Burn = Burn in mid-May of third growing season (1998)
Mow 2X = Mow to 6-inches on July1 and August 20 of second growing season (1997)
Mow 1X = Mow to 6-inches on July1 of second growing season (1997)
Mow & Roll = During second growing season, mow to 6-inches on July1 and flatten vegetation with tractor tires on August 20,1997
Mow & Burn = During second growing season, mow to 6-inches on July1 and August 20, 1997 and burn vegetatioin in mid-May of third growing season (1998)

Summary for the two Stem Abundance graphs above:

Whether mesic or dry-mesic late spring burns in the third growing season, increase stem abundance of prairie species on low phosphorous soils, at least for the short term. Also if the soil is phosphorous rich and the vegetation presumable very lush, it may be beneficial to mow a reconstructed prairie in early summer during its second season. Tractor tires rolling over and flattening the vegetation generally decreases stem abundance at least for the short term.

Summary for the two Species Diversity graphs above:

Under a control situation (no burning or mowing), mesic and dry-mesic reconstrucions tend to lose prairie-species diversity between the second and third year when growing on low phosphorous soils. However, one can increase (or preserve) diversity in both mesic and dry-mesic plantings by burning. If the prairie planting is dry-mesic and on high phosphorous soils, one might also increase its diversity by mowing it during the second year. However, the tire tracks created during mowing may cause some harm. If, on the other hand, the prairie planting is mesic, one should not mow in an attempt to increase diversity. However, as described in the first two graphs, mowing a mesic prairie in early summer during its second season may prove beneficial if increasing stem abundance is your primary goal and the prairie has been planted on phosphorous rich soil.

In summary: Conduct late spring prairie burns only on prairies growing on phosphorous poor soils. There is strong evidence that mowing a mesic prairie reconstruction twice (early-summer and mid-summer) during its second year causes considerable harm. Dry-mesic prairies are not as sensitive to such twice a year mowing. Soil phosphorous helps determine the affect of mowing and burning. More research should be done on soil phosphorous and how it relates to mowing, burning, prairie reestablishment, and weed control.