Last update: August 15, 2011 03:02:29 PM E-mail Print

 

GRAZING INDEX VALUES OF KAROO PLANTS

 

PCV du Toit / W van D Botha

Grootfontein Agricultural Development Institute

Private Bag X529

MIDDELBURG 5900

 

 

INTRODUCTION

The Ecological Index Method is used to estimate and compare grazing capacities in the Karoo. Index values were allocated on a group basis. Use of these values 'may lead to over- or under-estimation of the current grazing capacity. Caused partly by the disjunct nature of the series, and partly by the value accorded the climax grasses. To correct this shortcoming, the index values were subjectively adjusted by means of a species by species comparison. The grazing values are continuous and range from 0.7 to 10.

 

METHOD

Each species was assessed on the basis of the following six parameters:

 

  1.     The ability of the species to produce forage.
  2.     Forage value during the growing season.
  3.     Forage value during the dormant season.
  4.     Ease with which the species can be grazed.
  5.     Perenniality.
  6.     Ability of the plant to protect the soil.

 

RESULTS

The grazing values distinguishes between closely related species. with known different grazing values.

 

CONCLUSIONS

Regressing veld condition score on rainfall, using grazing values of species (R2 = 0.874) agrees closely with the regression of applied stocking rates of rainfall (R2 = 0.888). Regressing the ElM computed veld score on rainfall results in a poorer fit (R2 = 0.752). Computed veld condition scores and calculated grazing capacities for four sample sites are compared.

 

  % SCORE 1 SCORE 2

Sweet grassveld

Total

E G C 3 (ha/LSU)

90

 

894.0

5.14

 

698.6

6.65

Bushman grassveld

Total

EGC3(ha/LSU)

67

 

649.0

7.14

 

456.0

10.10

Karoobush veld

Total

E G C 3 (ha/LSU)

63

 

225.0

20.50

 

282.0

16.40

Mixed grass/karoobush veld

Total

E G C 3 (ha/LSU)

68

 

404.0

11.40

 

395.0

11.70

1 -  ElM index values

2 - Grazing values

3 - Estimated Grazing capacity

 

Published

Arid zone ecology forum 30 - 31.