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Extension > Agriculture > Dairy Extension > Forages > Quality assessments of alfalfa/grass mixtures

Quality assessments of alfalfa/grass mixtures

Jim Paulson

Published in Dairy Star November 5, 2010

In an earlier article (August 28, 2010, by Paul Peterson), data showing forage dry matter yields and grass content was presented for ongoing alfalfa/grass mixture plot work for two locations in Minnesota–Hutchinson and Underwood. The article, Alfalfa/Grass mixtures look promising on MN farms, is available on the Dairy Extension website. Presented in Tables 1 and 2 are data for quality assessments of the forage mixtures harvested for three cuttings in 2010 at these locations.

There are considerable differences between locations for the amount of grass in the plots. By visual assessment, Underwood plots averaged 29 percent grass while Hutchinson averaged just 11 percent. Tables 1 and 2 are set up in descending order of dry matter yield at the Underwood location. At the Hutchinson location, orchard grass was the highest yielder followed by tall fescue, meadow fescue, meadow brome, perennial rye grass, reed canary grass, smooth brome, alfalfa alone, and lastly timothy as in Underwood. Yields through four cuttings averaged 5.9 ton DM per acre at Underwood and 4.8 ton DM per acre at Hutchinson. Quality data on fourth cut harvest is not available at this time.

Examining the data, we observe several things. First, there are greater differences between cuttings than between locations within cutting. The predominant forage was alfalfa in both locations. The amount of grass in the mixtures was higher at Underwood than at Hutchinson. In each cutting and location and between locations, values for crude protein and NDF were similar. A greater effect is shown between locations for first harvest, which may be due more to cutting date than location. Also noteworthy is the decline in CP, NDF, and RFQ with each successive cutting. This is likely due to the increasing temperatures of the growing season, which has a negative correlation to forage quality, especially with cool season grasses as were used in these plots. It may also be an effect of days between cuttings, which reinforces the importance of a timely first cutting and a set schedule for harvesting later cuttings.

The reasons for including grasses in a forage program are to increase the amount of digestible NDF in the forage of the diet while adding effective fiber and more rumen mat. Grasses will also help forage dry faster, utilize nitrogen from the alfalfa, and add to yield potential. Data thus far would indicate that mixed stands of alfalfa and cool season grasses can compete with alfalfa alone for yield and quality.

Table 1. Average Quality Assessments of Forage Mixtures at Hutchinson, 2010.

Forage Type

1st Harvest
May 28

2nd Harvest
Jun 29

3rd Harvest
Jul 29

CP

NDF

RFQ

CP

NDF

RFQ

CP

NDF

RFQ

TF

22.3

41.7

158

19.0

46.3

126

19.4

47.1

126

None

21.9

43.1

144

19.9

45.1

127

20.0

45.9

125

MF

20.2

44.9

145

18.4

48.7

121

19.1

49.9

114

RCG

20.9

44.6

137

20.1

43.9

133

19.9

45.8

124

MB

21.3

43.9

143

19.9

45.4

127

20.2

46.5

124

OG

19.2

49.8

126

17.6

51.0

120

18.9

51.2

119

PRG

21.2

43.2

148

18.5

49.1

114

19.0

49.2

118

SB

22.4

41.2

152

20.0

45.2

127

20.5

44.6

135

TIM

20.0

47.9

132

20.2

44.2

135

19.8

47.7

121


Table 2. Average Quality Assessments of Forage Mixtures at Underwood, 2010.

Forage Type

1st Harvest
May 20

2nd Harvest
Jun 22

3rd Harvest
Jul 28

CP

NDF

RFQ

CP

NDF

RFQ

CP

NDF

RFQ

TF

21.7

44.2

150

18.9

47.8

130

17.1

52.6

101

None

22.3

44.6

138

20.1

43.8

123

18.0

50.9

108

MF

22.8

43.4

157

18.7

47.7

143

17.2

50.1

124

RCG

22.9

42.8

151

20.7

43.2

135

18.4

48.5

105

MB

22.4

44.5

144

20.9

44.1

138

18.0

52.0

99.5

OG

22.5

44.6

154

17.8

50.2

132

17.9

50.8

117

PRG

22.2

44.2

140

21.7

41.5

136

18.4

48.2

105

SB

22.4

47.1

130

20.3

46.9

125

18.1

51.0

98

TIM

21.7

45.4

152

18.2

47.9

129

19.0

49.0

113

Key: TF: tall fescue; MF: meadow fescue; RCG: reed canary grass; MB: meadow brome; OG: orchard grass; PRG: perennial rye grass; SB: smooth brome; TIM: timothy; none: pure alfalfa; CP: crude protein; NDF: neutral detergent fiber; RFQ: relative forage quality.

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