Management Impact on Sustainability of Native Legume Component of Warm-season Grass Pastures

Final report for OS14-085

Project Type: On-Farm Research
Funds awarded in 2014: $14,308.00
Projected End Date: 03/14/2017
Grant Recipient: LSU
Region: Southern
State: Louisiana
Principal Investigator:
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Project Information

Abstract:

Response of herbaceous mimosa (Mimosa strigillosa) to grazing deferment during various periods within the growing season indicated high resiliency of this species to management. Although none of the three 2-month grazing deferment periods appeared to increase seed production enough to enhance stand, it is important to realize these management treatments also did not lead to stand reduction. This finding indicates this native legume can be included in pasture management systems ranging from continuous stocking to long term deferment. This species also proved to be tolerant of flooding up to 4 weeks duration and to late season drought.

Project Objectives:

Determine impact of grazing exclusion timing on stand enhancement and persistence of the native legume herbaceous mimosa (Mimosa strigillosa).

Cooperators

Click linked name(s) to expand
  • Kun Jun Han
  • Greg Kincaid
  • W. D. Pitman

Research

Materials and methods:

A privately owned pasture with a natural extensive stand of herbaceous mimosa (Mimosa strigillosa) in Franklin Parish Louisiana was used to evaluate responses of the native legume to defoliation treatments. Defoliation treatments included continuation of the management approach that included minimal grazing rotation which had allowed the legume to survive in a commercial pasture production system and less-frequent defoliation involving protection from grazing during periods of the growing season. Temporarily installed wire exclusion cages provided deferment from grazing during either spring (May and June), summer (July and August), or autumn (September and October). Effects of the three deferment treatments (caged sites) on seasonal distribution of forage, forage nutritive value through the growing season, seed production, and density of the legume stands were determined by sampling in late June, late August, and late October at the end of each of the three grazing deferment periods. Each of these treatments was replicated four times for a total of twelve caged sites. Caged sites for a particular season and four unique uncaged sites were sampled at the end of the respective seasons. June sampling was from the spring-deferred treatment and four non-caged sites. Sites caged in spring were sampled again in August and October (but not from previously clipped portions of the area) to assess any residual effects of the treatment. Sites caged in summer were also sampled in October to assess residual effects. Overall treatment effects were assessed with ratings of stand density from an area within each treatment that was never included in the mechanically harvested area. This evaluation was done as new growth was initiated in the spring after winter dormancy and compared with pre-treatment stand density measures made at initiation of the experiment. Treatments were continued at the same sites through the two years.

Cages were circular with about a 3-m diameter. Pasture samples from 0.5 m2 were clipped to ground level, separated into herbaceous mimosa and other components, hand processed to remove seed pods, oven dried, and weighed for dry matter determination. Sub-samples were taken for evaluation of forage nutritive value including crude protein and fiber components. A frame with 10-cm by 10-cm grids was used to determine percent of the 0.5 m2 sample area which included the legume immediately before sampling. Measures of forage nutritive value of herbaceous mimosa was compared to those of the associated grass to assess potential of the legume to function as supplement to the grass pasture.

Research results and discussion:

There was a significant improvement in herbaceous mimosa stands over the study period as determined from areas in each treatment that were never mechanically harvested. Herbaceous mimosa stands improved from 20 to 29 percent from May 2015 to May 2017, respectively (data not shown). Plant stands were similar between the May 2015 and 2016 evaluations but this stand increase was evident at the May 2017 evaluation and thought to be a result of increased seed germination following the flooding in spring 2016.   Plant stands were maintained in all management treatments throughout the trial period and did not differ among treatments in any evaluation period.

There were rather extreme weather conditions that occurred during both years of the trial. During the 2015 growing season the area received minimal rainfall (<13 mm) from the first week of July until the final week of October. The trial area was submerged by flood waters (reaching approximately 60 cm depth) for more than 4 weeks during late March to mid-April 2016 and again experienced drought from the latter part of August until the last week of November 2016. Owing to these drastic differences between years, results are presented separately for each year.

During 2015, there was significantly more forage in each cage area at the end of each grazing exclusion period compared to that in continuously stocked areas (Table 1). This enhanced forage availability in the grazing exclusion areas remained through the season even after the exclusion cages were removed from an area. This indicates the animals had enough forage outside the exclusion areas to meet consumption requirements and did not have to utilize the older growth even though they had access to it. Cattle were removed from the test pasture in mid-March 2016 because of flooding and did not return until early July. So there was no grazing outside the May/June exclusion area while the exclusion cages were in place which resulted in there being no difference in forage availability between the area excluding grazing and outside the cage.  Although the pasture was stocked during most of the time the July/August grazing exclusion cages were in place forage availability at the end of this period was similar throughout the field.  The area excluded from grazing during September/October 2016 accumulated significantly more forage than the area outside the caged area.  The previously caged areas and the area not caged had similar amounts of forage at the end of October.

Herbaceous mimosa made up a small part of the total forage harvested at each harvest date. The small amount of herbaceous mimosa in some collected forage samples resulted in often having to combine mimosa samples for forage quality analysis. Forage quality values are presented without statistical analysis (Table 2). Herbaceous mimosa maintained relatively good quality throughout the season and could enhance nutritive value of warm-season perennial grass pastures throughout the southeastern USA.

Results indicate a resilience of herbaceous mimosa to persist in a warm-season perennial grass base pasture through rather drastic climatic as well as management stresses. The capability to survive through these conditions shows this species has potential as a pasture crop throughout the southeast USA. This native legume could enhance forage quality in pastures utilizing perennial warm-season grasses as the forage base.

 

Table 1. Grazing exclusion period impact on yield and stand of warm-season perennial grass pasture containing herbaceous mimosa (Mimosa strigillosa).

 

Harvest

Exclusion

   

Mimosa

Mimosa

 

Date

Period

Yield

 

Stand

Yield

     

kg/ha

 

%

%

2015

           
 

July 7

         
   

May/June

5721

A§

18

2

   

None

2468

B

20

2

             
 

Aug. 28

         
   

May/June

6959

A

12

1

   

July/August

5538

A

14

1

   

None

2761

B

21

2

             
 

Nov. 5

         
   

Sept/Oct

1370

A

1

0

   

May/June

1287

A

0

0

   

July/August

1252

A

0

0

   

None

450

B

2

0

             

2016

           
 

July 8

         
   

May/June

8164

NS

59

5

   

None

6814

 

48

4

             
 

Sept. 7

         
   

None

15233

NS

34

3

   

July/August

13149

 

45

3

   

May/June

12919

 

37

4

             
 

Oct. 28

         
   

Sept/Oct

15955

A

11

0

   

July/August

8297

B

14

0

   

May/June

7976

B

27

1

   

None

7424

B

15

1

Stand determined by quantifying number of 10cm X 10cm square cells inhabited by herbaceous mimosa divided by 50 (10cm X 10cm possible squares in .5 m2 harvest area).

Mimosa yield is the percentage of total yield from herbaceous mimosa.

§Forage yield within each harvest date followed by the same letter does not differ (P>F = .05) (NS = not significant).

 

Table 2. Forage quality parameters of herbaceous mimosa (Mimosa strigillosa) and bahiagrass (Paspalum notatum Flugge).

 

Harvest

       
 

Date

Species

CP

NDF

ADF

     

———————— % ————————

2015

         
 

July 7

       
   

Mimosa

15.4

39

22

   

Grass

8.6

67

33

           
 

Aug. 28

       
   

Mimosa

15.3

34

21

   

Grass

—–

           
 

Nov. 5

       
   

Mimosa

—–

   

Grass

10.7

65

36

           

2016

         
 

July 8

       
   

Mimosa

15.4

48

32

   

Grass

7.3

66

34

           
 

Sept. 7

       
   

Mimosa

12.4

42

30

   

Grass

7.7

70

38

           
 

Oct. 28

       
   

Mimosa

11.6

41

29

   

Grass

5.2

71

38

 

Participation Summary
1 Farmer participating in research

Educational & Outreach Activities

1 Webinars / talks / presentations
1 Workshop field days

Participation Summary

84 Farmers
45 Ag professionals participated
Education/outreach description:

Information from this study was presented at the Louisiana Forage and Grassland Council annual meeting in December 2015. This meeting was attended by approximately 100 producers and other agricultural professionals as well as 5 FFA students from the state of Louisiana.

A field day was held at the study site in May 2017 and results from this study and other studies involving herbaceous mimosa were presented. The field day was attended by 53 people including producers, other agricultural professionals and 11 FFA students from four high schools in the surrounding area.

Learning Outcomes

7 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation

Project Outcomes

Project outcomes:

Presentations of results from this study have introduced producers and agricultural professionals to the potential for utilizing herbaceous mimosa as a forage crop. Several producers have mentioned noticing this species in their pastures but not being aware of the potential as a warm-season legume forage crop. Producers from different regions of the state have contacted study participants requesting more information on management of this species in pastures.

Recommendations:

While this study has provided a basis for introducing herbaceous mimosa to producers as a forage crop there are several aspects that need further study. Methods for establishing this species in an existing warm-season perennial grass sward need to be evaluated. Since herbaceous mimosa is seldom more than a minor component of frequently grazed pastures despite wide adaptation, grazing management approaches contributing to vigor and expansion of populations of the legume are of particular interest. Populations of this legume spread readily under favorable conditions from both extensive stolon growth and vigorous seed production. Increases in vigor and growth could also contribute to greater forage productivity and opportunity for increased nitrogen fixation. Further research is needed to evaluate management that will enhance stands once established. This species offers considerable potential to improve forage quality in pastures throughout the southeast US but response to various agronomic practices needs to be clarified before promoting widespread use.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.