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Home > Protecting Our Lands & Waters > Conservation > Post-CRP Management Options & Issues > Persistence of Planted Forages

Persistence of Planted Forages


Craig C. Sheaffer, Jane Grimsbo Jewett, and Roger L. Becker, University of Minnesota

The information presented in this fact sheet is not intended to take the place of professional legal advice. In developing any written lease agreement, it is highly recommended that all parties seek professional legal advice.

Summary

  • In future plantings for long-term land retirement, smooth bromegrass and reed canarygrass should be noted as superior cool season species. Switchgrass and big bluestem are the most successful warm season species.
  • Alfalfa and birdsfoot trefoil were the most persistent planted legumes in “cool season” fields, but their average ground coverage was only about 25 percent. In future CRP plantings, clipping may be necessary to increase legume survival. If planning future livestock production, legumes may need to be seeded in some CRP fields. On average, soil P, K, and pH did not change between the start of the CRP contracts and 1994. Many fields can support good crop growth, but soils should be tested before resuming cropping or grazing.
  • Weeds and volunteer plants covered almost one-third of the average CRP field. About 10 percent of the ground was bare in “cool season” and “warm season” fields, but almost 30 percent was bare in “existing vegetation” fields. Farmers should evaluate their CRP fields for weeds. Weeds may need control, depending on future land use.

A Survey of CRP Fields

When farmers began planting permanent cover on CRP fields in 1986, the long-term survival of grasses and legumes on fields with minimal management was unknown. To understand the long-term survival of these fields better, a survey of 151 CRP fields planted from 1986 to 1988 in 10 counties across Minnesota was conducted in 1994 (see Other Resources #1). The following field types were surveyed:

  • 108 "cool season" fields (planted to cool season grasses or grass-legume mixtures);
  • 17 "warm season" fields (planted to native warm season grasses); and
  • 26 "existing vegetation" fields (accepted into CRP with existing vegetation).

In each surveyed field, the grass, legume, and weed species were identified, and the amount of ground covered by each species was estimated. Soil samples from each field were tested for phosphorous (P), potassium (K), and pH. The amount of gopher mounding also was estimated.

Figure 1. Coverage of the average cool season field in 1994 after 6-8 years in CRP.To plan for future uses of CRP land, landowners should evaluate the composition of the existing CRP vegetation, assess weed problems, and test the soil. This information sheet gives an idea of what Minnesota CRP land-owners can expect to find, based on a survey of 151 fields. Weeds and Pocket Gophers in this series provides more details about weeds in the surveyed fields and also reports on the degree of gopher mounding.

Survey Results: Vegetation Status

(The numbers given here are rounded off; see Table 1 and Table 2 for exact figures.)

Cool Season Fields
Half of the average "cool season" field was covered by grasses and almost one-fourth was covered by legumes. About 20 percent of the average field was covered by weeds and almost 10 percent of the ground was bare (Figure 1). Ninety percent of fields planted to grasses and 80 percent of fields planted to legumes retained these covers.

Alfalfa and birdsfoot trefoil were the most persistent legumes (Table 1). Alfalfa covered one-fifth and birdsfoot trefoil covered nearly one-third of the ground in fields planted to these legumes at the start of CRP. This suggests that alfalfa and birdsfoot trefoil have good longterm survival.

Table 1. Legume Survival and Cover in 108 Cool Season Fields Surveyed in 1994

Legume species

Fields planted to species*

Fields with surviving plants**

Average ground cover

Alfalfa

57%

90%

21%

Birdsfoot trefoil

28%

67%

32%

Red clover

17%

50%

8%

Alsike clover

40%

44%

2%

Sweet clover

26%

39%

>1%

* Total exceeds 100 percent since some fields were planted with more than one species.

** Only fields with surviving plants of a species were used to calculate the average for that species.

Smooth bromegrass and reed canary grass were the most persistent grasses, surviving in all of the fields in which they were planted. This is probably because they spread by underground stems (rhizomes) and are very winter hardy (Table 2). Smooth bromegrass covered half and reed canary grass covered about three-fourths of the ground in those fields. Half of the fields planted to timothy retained it by 1994, with an average ground cover of 10 percent. Orchard grass also persisted in half of the fields where it was planted, but its average ground cover was only 3 percent.

Table 2. Grass Survival and Cover in 108 Cool Season and 17 Warm Season Fields Surveyed in 1994

Grass species

Fields planted to species*

Fields with surviving plants**

Average ground cover

Cool season fields:

Reed canary grass

4%

100%

77%

Smooth bromegrass

63%

100%

51%

Timothy

79%

52%

9%

Orchard grass

31%

58%

3%

Warm season fields:

Switchgrass

100%

94%

50%

* Total exceeds 100 percent since some fields were planted with more than one species.

** Only fields with surviving plants of a species were used to calculate the average for that species.

Warm Season Fields
Switchgrass was planted in most of these fields. Farmers seeded a few fields to big bluestem or Indian grass. Half of the average "warm season" field was covered by switchgrass, and more than 10 percent was bare (Figure 2). Weeds or volunteer (non-planted) grasses and legumes such as alfalfa, alsike clover, and smooth bromegrass covered the remaining ground.

Existing Vegetation Fields
These fields usually contained an alfalfa-grass mixture. Legumes covered 2 percent and grasses covered almost half of the average "existing vegetation" field. Over one-fourth of the average field was bare, while weeds or other volunteer legumes and grasses covered the remaining ground (Figure 3). The "existing vegetation" fields had more weeds and bare ground than the "cool season" or "warm season" fields. This is possibly due to the age and thinned condition of their grass-legume stands at the start of the CRP contracts.

Figure 2. Coverage of the average warm season field in 1994, after 6-8 years in CRP.    Figure 3. Coverage of the average existing vegetation field in 1994, after 6-8 years in CRP.        

Survey Results: Soil Fertility

Fields enrolled in CRP needed adequate pH levels, phosphorus (P), and potassium (K) for grass and legume growth. Three-fourths of "cool season" fields had enough P and about half of the fields had enough K at the beginning of the contracts to support 2 tons per acre per year of grass-legume forage. On average, soil P, K, and pH did not change between the start of the contracts and 1994. Many fields can support good crop growth, but soils should be tested before resuming cropping or grazing. Additional fertilization and liming may be necessary for some future uses (see Other Resources #4).

Other Resources

  1. A Survey of CRP Land in Minnesota (1996). Craig Sheaffer, Department of Agronomy and Plant Genetics, 411 Borlaug Hall, University of Minnesota, St. Paul, MN 55108. 612-645-7224.

The following publications are available from your local Minnesota Extension Service (MES) office or the MES Distribution Center, University of Minnesota, 20 Coffey Hall, 1420 Eckles Avenue, St. Paul, MN 55108-6069. 612-624-4900 or 1-800-876-8636.

  1. Reed Canarygrass Variety Trials Annual publication
  2. Alfalfa Management Guide (1994). Item #AG-BU-5798.
  3. Fertilizer Recommendations for Agronomic Crops in Minnesota (1994). Item #6240-E.
MDA Contact

Barbara Weisman, Conservation Program Specialist
barbara.weisman@state.mn.us
651-201-6631 or 1-800-967-2474
Ag Marketing & Development Division