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Forages in Oil Palm and Rubber Plantations in Malaysia

Hassan A. Wahab
Malaysian Agricultural Research and Development Institute (MARDI)
P.O. Box 62, 26700 Muadzam, Shah, Pahang, Malaysia

ABSTRACT

The forage resources under plantations in Malaysia was described with regards to  the factors affecting them, their quality, availability and their utilization for livestock production.  Forages under plantation crops consist of native grasses, legumes, broadleaf species and ferns, most of which are palatable to animals.  The botanical composition, yield and quality of these species are influenced by interacting factors of light, moisture and age of trees or plantation crop and kind of livestock raised.  Sheep however, was found most suited to be integrated with rubber.

INTRODUCTION

Oil palm and rubber are the major plantation crops in Malaysia.  They cover an estimated area of over 4 million hectares.  The inter row areas of these crops are usually covered with vegetation comprising of leguminous cover crops, grasses, broadleaf species and ferns which form a naturalized pasture and can be utilized as forages for livestock production.  This feed resource was estimated to comprise as much as 83% of the total forage resource available in the country (Devendra 1981).  It is one of the most extensive and underutilized forage resources in Malaysia.

There are about 60 to 70 plant species growing under the young plantation crops and the number decline to 20 to 30 species under older trees.  Out of these, only about 70% of these species are palatable and can contribute as forage for livestock production (Chen et al. 1978; Wan Mohammad 1977; Hassan and Abdullah 1991).

This paper discusses the forages resources that are available in oil palm and rubber plantations in terms of the species, botanical composition, quality, quantity as well as the utilization of these forages as animal feed and the impact to the livestock and oil palm/rubber industries in Malaysia.

Factors affecting forage resources under plantations
Forages under plantation crops consist of native grasses, legumes, broadleaf species and ferns, most of which are palatable or grazed by the animals.  If legume cover crops are sown at the time of planting of oil palm or rubber,  these legumes usually dominate the native species in the inter rows for the first three to five years. These legume cover crops are grown in combinations of Calopogonium mucunoides, C. caeruleum, Centrosema pubescens and Pueraria phaseoloides. They are planted for soil erosion control during the first 8-10 months of land clearing.   The species, botanical composition, yield and quality of these forages are constantly changing because of the influence of many interacting factors such as light and moisture. 

Light is the most critical factor in determining the type of forage species available and in determining the growth of the forage.  In the plantations, the amount of photosynthetically active radiation (PAR) that reaches the ground vegetation is proportionally reduced as it passes through the canopy of the trees.  The amount of light reaching the undergrowth varies with age, height, spacing and canopy characteristics of the tree crops.  Generally the amount of PAR declines with increasing age of the trees (Figure 1).

In rubber and oil palm, the percentage of light under the tree canopies drops to below 20% of full sunlight at the tree age of 6 to 7 years and this amount changes only slightly thereafter.  The percentage of light increases significantly after the trees are 15 to 20 years old when the canopies open up slightly.

Figure 1.  Light transmission (%) profiles in relation to age of oil palm and rubber
                 (Source: Wilson and Ludlow 1990)

It must be realized that under reduced light, that presence of the dry matter production of the native species is low.  These species are adapted to the environment through morphological adaptations.  Wong (1991) showed that shading significantly reduced tiller production, stem stubble and roots but increased the specific leaf area (leaf area per unit leaf weight), shoot:root ratio and leaf:stem ratio.

In Malaysia, the rainfall is high (>2000 mm per year) but is not evenly distributed. Thus, agro-ecological zones based on rainfall distribution have been recognized. Generally there is little competition for moisture between the tree crops and the native forages, except when there is a prolonged dry spell.

The air temperature under tree crops is generally lower than in the open.  Chen (1989) showed that air temperature under rubber was lower than in the open throughout the day with a maximum of 2 to 3°C during the afternoon.  Soil temperature also showed the same trend with 1to 2°C lower in the shade at 5 cm depth compared with open pastures (Chen et al. 1991).  In general, the decrease in air and soil temperature is too small to have any influence on native pasture growth under tropical environment (Wilson and Ludlow 1991).

Forage species
Forage species that grow in oil palm and rubber plantations include all the palatable plant species that thrive under this microenvironment.  Generally, the leguminous cover crops comprising of Pueraria phaseoloides, Calopogonium mucunoides, Calopogonium caeruleum and Centrosema pubescens dominate the ground vegetation in the early stages of the tree crop development (first 5 years) and they are gradually replaced by the shade-tolerant species when the canopies close.  These shade-tolerant species persist for almost two-third of the economic life span of the tree crops (Ahmad Tajuddin and Wan Zahari 1991).

Species richness under oil palm and rubber has been highlighted and recognized.  Species of grasses, broadleaves, legumes and ferns that are commonly found growing under oil palm and rubber in Malaysia are shown in Table 1.  These species have been grouped into palatable and non-palatable species and only those palatable species contribute to the forage resource available under plantation crops.

Palatable species are those that are ‘accepted’ or grazed by cattle and sheep.

Table 1.   Palatable and non-palatable plant species commonly found in oil palm and rubber plantations.

PALATABLE SPECIES

NON-PALATABLE SPECIES

Grasses

   Axonopus compressus

   Brachiaria mutica

   Chrysopogon aciculatus

   Cyrtococcum oxyphyllum

   Digitaria ascendens

   Eleusine indica

   Imperata cylindrica

   Ischaemum muticum

   Ottochloa nodosa

   Panicum repens

   Paspalum conjugatum

Broadleaves

    Asystasia intrusa

   Cleome rutidosperma

   Commelina nudiflora

   Croton hirtus

   Hydrocotyl asiatica

   Mikania cordata

Legumes

   Calapogonium mucunoides

   Centrosema pubescens

   Desmodium ovalifolium

   Desmodium triflorum

   Mimosa pudica

Pueraria phaseoloides

Ferns

   Lygodium flexuosum

   Nephrolepis biserrata

   Pteridium esculentum    

Grasses

    Themeda arguens

Broadleaves

  Ageratum conyzoides

  Borreria latifolia

  Eupatorium odoratum

  Hyptis brevipes

  Lantana camara

  Melastoma malabathricum

Legumes

  Calapogonium caeruleum

  Cassia tora

  Mimosa invisa

Ferns

Dicraopteris linearis

Stenochaena palustris

With regards to ferns, the animals do not lavish on them and they are normally grazed last after all the other palatable species have been grazed.

The non-palatable broadleaf species are mainly woody shrubs such as Melastoma, Clidemia, Eupatorium, Lantana and Hedyotis.  These species may comprise 10-30% of the total dry matter of forage depending on age of the tree canopy (Wong and Chin 1998).  

Forage botanical composition
Under plantation crops, the botanical composition of the forage changes as the trees become older.  This is due to the declining amount of light reaching the ground vegetation.  As the trees grow and become older, the canopies of the trees close up and the amount of light reaching the ground is reduced. Only shade tolerant species are able to grow under this environment. Under oil palm, grasses, legumes and broadleaf species dominated the native forage in the first five years after planting.  The legumes, mostly the cover crops decline in their contribution to the forage after the fifth year, once the oil palm canopy has closed up.  The proportion of grasses changes slightly but broadleaf species declined as the trees mature.  But ferns and non-edible broadleaf species which tolerate high shade increased in their proportion with the increase in age of the oil palm (Table 2). Under rubber, the scenario is slightly different.  The proportion of grasses declined with increasing age of the rubber trees even though the light penetration has increased slightly because the canopy has opened up towards the end of the economic life of the rubber trees. The legumes showed similar trend with that of grasses. Proportions of ferns and the non-edible broadleaf species increased with increasing age of the rubber trees.

Wong (1985, 1990) has screened forage grasses and legumes under different shade levels and grouped forage species both native as well as introduced into high, medium and low shade tolerance (Table 3).

Shade tolerance was defined as the relative growth performance of plants in shade compared to that in full sunlight as influenced by regular defoliation. It embodies the attributes of both dry matter productivity and persistence of the species.

Table 2.  Botanical composition (% dry matter) and forage dry matter available (kg/ha) under different age groups of oil palm and rubber canopies

Age of palm /tree (years)

3

5

10

15

20

25

30

OIL PALM

 Grasses

 Legumes

 Edible dicots

 Ferns

 Non-edible dicots

DM yield (kg/ha)

 

39.76

28.65

22.54

0.16

8.78

2990

 

59.04

5.66

18.50

3.75

3.05

2164

 

55.64

0.50

13.00

23.60

7.2

475

 

52.46

0.40

8.08

19.41

19.65

825

 

37.80

5.55

5.59

26.86

24.20

467

 

26.25

2.22

17.69

37.79

17.05

343

 

31.20

-

8.44

32.50

27.85

998

RUBBER

 Grasses

 Legumes

 Edible dicots

 Ferns

 Non-edible dicots

DM yield (kg/ha)

 

53.35

31.28

8.22

-

7.16

1869

 

52.12

15.97

8.93

18.21

4.77

435

 

59.99

2.07

2.52

31.33

4.06

542

 

21.82

6.32

4.94

62.27

4.65

520

 

19.18

4.26

1.00

58.00

17.55

628

 

13.57

1.43

3.66

63.18

18.16

1282

 

12.89

3.78

7.25

55.84

20.23

1975

Source: Chen et al. (1991)

Table 3. Shade tolerance of some tropical forage

Shade tolerance

Grasses

Legumes

High

Axonopus compressus

Brachiaria miliiformis

Ischaemum aristatum

Ottochloa nodosa

Paspalum conjugatum

Stenotaphrum secundatum

Calopogonium caeruleum

Desmodium hetrophyllum

Desmodium ovalifolium

Flemengia congesta

Medium

Brachiaria bizantha

Brachiaria decumbens

Brachiaria humidicola

Digitaria setivalva

Imperata cylindrica

Panicum maximum

Pennisetum purpureum

Setaria sphacelata

Calopogonium mucunoides

Centrosema pubescens

Desmodium triflorum

Pueraria phaseoloides

Desmodium intortum

Leucaena leucocephala

Low

Brachiaria mutica

Cynodon plectostachyus

Digitaria decumbens

Digitaria pentzii

Stylosanthes hamata

Stylosanthes guianensis

Zornia diphylla

Macroptilium atropurpureum

Source: Wong (1990)

The forage species that tolerate high shade are those native forage species commonly found growing under plantation crops.  Axonopus compressus, Ischaemum aristatum, Ottochloa nodosa and Paspalum conjugatum are the major grass species while Desmodium heterophyllum and D. ovalifolium are the native legumes.  Calopogonium caeruleum and Flemengia congesta are not palatable to livestock.

The medium shade tolerant species are found in the plantation in the first five years after planting of the plantation crops and they decline thereafter because the tree canopies have close up and less light can penetrate through to the ground.  If one needs to plant forages in the plantations, then these medium shade tolerant species are suitable because they can provide high forage production up to five years before light becomes limiting.

In terms of morphological adaptations of the plants to shade, tiller production and leaf, stem, stubble and root productions are often reduced at low light with formation of thinner leaves with higher moisture content and higher specific leaf area  (Wong et al. 1985a, b). Grasses with high shade tolerance were found to have a higher specific leaf area and leaf area ratio than those with low shade tolerance.

Quality of native forage
Contrary to general belief that native forages are low in quality, the nutritive values of grazed native pasture species under plantation crops are high.  The crude protein content of native grasses on offer ranges from 6.7 to 11.4 % (Lane 1984; Chen et al. 1991).  It is quite common that the animals through selective grazing may consume forages with 16% crude protein or even higher especially when grazing broadleaves and legumes.

The estimated concentrations of metabolizable energy (ME) are 7.1 to 8.9 MJ/kg dry matter (DM) for grasses on offer and up to 10.1 MJ/kg DM for forages consumed (Ahmad Tajuddin and Wan Zahari 1991).    Chen et al (1991) reported ME values of 7.13, 7.17, 5.34 and 8.34 MJ/kg DM for grasses, legumes, ferns and edible broadleaves, respectively.

Table 4. Proximate analysis of some of the palatable native forages under oil palm and rubber.

Species

DM
(%)

CP
(%)

CF
(%)

EE
(%)

P
(%)

Ca
(%)

Mg
(%)

ME 1
MJ/kg)

Axonopus compressus

29.6

7.5

30.8

1.4

0.05

0.39

0.36

8.7

Brachiaria mutica

27.5

6.3

32.4

1.8

0.08

0.14

0.04

8.2

Imperata cylindrica

36.5

11.7

32.0

1.9

0.10

0.20

-

9.2

Ischaemum muticum

35.0

14.9

27.7

1.6

0.07

0.30

0.13

10.6

Paspalum conjugatum

21.7

11.0

28.6

1.6

0.09

0.31

0.43

9.2

Asystasia intrusa

12.1

19.0

25.6

3.3

0.31

0.50

0.50

11.7

Mikania cordata

9.6

17.6

22.9

2.4

-

-

-

11.3

Calopogonium mucunoides

23.0

20.1

24.8

65.3*

-

-

-

-

Centrosema pubescens

24.3

22.2

30.9

62.7*

-

-

-

-

Pueraria phaseoloides

19.1

19.9

28.8

67.4*

-

-

-

-

* TDN (%)
1 Metabolizable Energy (MJ/kg DM) = 13.3 + 0.17 (CP) – 0.19 (CF)
Adapted from Ahmad Tajuddin and Wan Zahari (1991) and Chin (1991)

The nutritive values of some common native pasture species under plantation crops in Malaysia are shown in Table 4.  Besides the leguminous cover crops of C. mucunoides, C. pubescens and P. phaseoloides, Assassin intrusa and Mikania cordata have also high levels of crude protein. They are very palatable and thus making them excellent forage species.

Even though native grasses have slightly lower crude protein content (6 to 11%) for good animal growth requirement, the fact that they exist in combinations with broadleaves such as Asystasia and Mikania and with leguminous cover crops which contain high crude proteins make them good forages.  Rosli (1998) reported that a combination of 60% Asystasia and 30% Paspalum can be considered as good forage. In terms of animal nutritional requirements,  Wong and Chin (1998) showed  that the edible forage resource at different ages of the oil palm plantation are adequate to the grazing cattle in terms of metabolizable energy  and more than adequate for crude protein requirement (Table 5).

Table 5. The botanical composition and estimated forage quality under different ages oil palm

Age of oil palm (years)

Botanical composition (%) Forage Quality
Grasses    Dicot Legumes Ferns

Mean
ME
(MJ/kg)   

Mean
Protein
(%)           
Mean
Ca
(%)           
Mean
P
(%)           
3-5 65 23 19 2 7.42 12.8 0.25 0.30
6-10 64 18 3 15 7.31 11.8 0.59 0.27
›10 50 13 2 35 6.87 12.2 0.63 0.23

Source:  Wong and Chin (1998)

Table 6 shows the quality of native forages under plantations as compared to the quality of guinea and legumes under legume-based pasture and improved grasses under nitrogen fertilized pasture. Forages under plantation were comparable to legume based pasture in terms of N content, dry matter digestibility and metabolizable energy.  However, quality of native forages is slightly lower than that of N fertilized grasses.

Production system

N
(%)

DMD
(%)

ME
(MJ/kg DM)

a) Under Plantation

           Grasses

           Legumes

           Ferns

           Edible dicots

b) Legume-based pasture

          Guinea

          Legumes

          Weeds 

c) N-fertilized pasture

          Digitaria setivalva

          Guinea

          Signal grass

 

1.58

3.07

1.96

2.81

 

1.60

3.55

1.97

 

2.61

2.54

2.39

 

47.61

47.80

35.60

55.60

 

52.62

40.33

48.04

 

59.40

52.62

56.09

 

7.13

7.17

5.34

8.34

 

7.80

6.01

7.13

 

8.78

7.80

8.31

Source:  Wong and Chin (1998)

AVAILABILITY OF FORAGES

Forage dry matter yield was strongly related to light transmission through the canopy to the ground vegetation.  Available forage dry matter declines from over 5 tons/ha in young rubber and oil palm plantation to below 1 ton/ha when the canopy closed (Chen and Othman 1983; Tajuddin and Chong 1994).  Similar trend was also obtainedby Chen and Harun (1994) which they reported  dry matter yield of 1230 kg/ha dry matter under 7 year old palm, while under 17 year-old palm, the forage yielded only 411 kg/ha dry matter.  The productivity of native pasture has been estimated conservatively to range from 3 tons/ha/year at establishment to as low as 435 kg/ha/year in the mature phase (Chen et al. 1991).  Figure 2 shows the changes in dry matter yield of ground vegetation in relation to age of oil palm and rubber.

Figure 2. The forage dry matter yield in relation to ages of oil palm and rubber.

Attempts had been made to increase forage productivity under oil palm and rubber through planting of improved grass species in the plantations or more recently through modifications of the planting patterns of the palm/trees to increase light transmission without changing the total number of trees/ha.   Chen et al. (1978) reported planting guinea grass and stylo under five year old oil palm. But the grass and legume productivity declined after two years of cattle grazing and improved species were replaced by native species.  Inter cropping of guinea and napier grasses under rubber were only possible for the first three years of planting.  Yields in second and third year were only 80% of the first year.   However, after five years, the yield dropped significantly low to only 30% of first year’s yield (Najib 1989) and therefore not viable to grow improved grasses after five years. Although the production of improved forages is good in the early stage of the plantation, their poor persistence and survival have limited their utilization unless proper management is adopted.

Modifications of planting patterns have been studied in oil palm and rubber. These modifications are designed to provide a long term high light environment in the interrows for longer forage productivity. Double hedge row is a planting pattern in which two rows of oil palm or rubber are interspaced with a wide open area for pasture without changing the plant density.   In oil palm, the conventional planting was triangular 9.2m x 9.2m x 9.2m with 138 palms/ha.  In double hedge row, the planting pattern was triangular 6.7m x 6.7m x 6.7m interspaced between the two rows with 15.2 m open space (Abdullah and Shukri 1997).  They reported that with the increased in forage dry matter yield, the double hedge row system could support 3 to 4 heads of sheep/ha  compared to only 2 to 3 sheep/ha under conventional system when the palm were more than 7 years old.

In rubber, conventional planting patterns were either 6mx4m with 416 trees/ha or 4.8mx4.5m with 462 trees/ha or 9mx2.5m with 444 trees/ha.  In the double hedge row planting pattern, trees were planted in double rows with 2mx3m spacing and the double rows were separated by wide interrows of 22m.  The rubber rows were aligned East-West direction to intercept maximum light in the interrows.  In the wide interrows, improved pastures were planted instead of the conventional leguminous covers (Chong and Tajuddin 1994).  They showed that early growth and yield of rubber in double hedge row planting were comparable to those of conventional planting system. They also reported increased forage yield as well as increased sheep live weight gains.

Utilization of forages
Under oil palm, animals can be released for grazing 18 to 20 months after field planting when the young shoot are beyond the reach of the animals.  Grazing management under plantation requires a systematic and flexible system to equate animals stocking rate with forage availability.  Surplus stock needs to be sold or transferred to another area to avoid deleterious effects of overgrazing.  In young oil palm, 3 Kedah-Kelantan steers/ha can be kept for two years until they are finished off. An average daily gain of 320 g/head had been reported.   Subsequently the stocking rate could be adjusted to 2 and 1 Kedah-Kelantan cattle/ha for a period of 2 years when the canopy is closed.  Lower carrying capacity of 0.3 to 0.4 Kedah-Kelantan cattle/ha may be adjusted on native pasture depending on season, soil type, age of oil palm and plantation management (Chen et al. 1978; Chen et al. 1991).

Sheep had also been successfully integrated with oil palm. The stocking rate depends on the availability of native forages under the palm.  The recommended stocking rate for 2 to 6 years old palm is 6 to 10 sheep/ha.  In terms of animal productivity, local breed of sheep under oil palm attained weight of 22.2 kg in 9 months compared to 17.9 kg at one year of age under rubber (Abdul Rahman 1987).

Sheep is the most suitable animals to be integrated with rubber.  Cattle and goats can cause damage to the rubber trees because of cattle’s trampling effects and goat grazing habit.  Sheep can be introduced under immature rubber when the trees are more than two years old and when the height of the lowest whorl of leaves is more than two metres above the ground.  The recommended stocking rate is 6 to 8 sheep/ha for immature rubber trees and 3 to 5 sheep/ha for mature trees (Tajuddin and Chong 1988).

A study by Chong et al. (1990) showed that the initial high level of native forage production under immature rubber (3 years old) of about 2200 kg/ha could support a high stocking rate of 17 sheep/ha with animal productivity of about 400 kg/ha/year.  However, stocking rate had to be steadily reduced as forage dry matter yield declined under maturing rubber trees.  In mature rubber (7 years old), native forage availability was less than 600 kg/ha and this could only support 2 to 3 sheep/ha with animal productivity of only 72 kg/ha/year.

Meeting the nutritional requirements of ruminant under declining forage resources in mature plantation is important for livestock management and production (Wong et al 1988; Chen and Shamsuddin 1991; Abdullah et al 1997).   Low forage availability has been reported to lower conception rate (52%) of Kedah-Kelantan cows with access to fertile bull year round and grazing on native forages in 10 to 15 years old oil palm plantation (Wan Mohamad et al 1987). There was an increasing trend of anestrous animals towards the end of the second year.  Currently, successful integrated farms use low stocking rate of 0.25 to 0.5 animal unit/ha under mature trees.  

CONCLUSION
In the plantations, plants that grow in the inter rows are considered weeds by the plantation management and they are controlled by using herbicides.  Only ‘soft grasses’ such as Axonopus compressus, Paspalum conjugatum and Ottochloa nodusa are tolerated.   The average cost of weed control in oil palm plantation is about RM 100 /ha/year. In the last few years, with the economic slow down and higher cost of herbicides, and with support from the government in terms of soft loan to buy cattle, many of the big oil palm plantations have embarked on the utilization of these ground vegetation for animal feed by integrating cattle with oil palm. For example, FELDA Farm products have a total cattle population of over 20,000 and ESPEK Risda with over 12,000 heads. All these animals are integrated with oil palm. This environmental friendly technique of weed control using cattle as grazers has been shown to cut costs in terms of herbicide and labor costs an estimated 10 to 20% in the first year and up to 30 to 40% after three years of grazing.  Other added advantages of integration are the additional income from sales of animals and increased yields of the oil palm mainly due to the recycling of the dung and urine in the plantation.

ACKNOWLEDGEMENT
The author wishes to thank the Director General of MARDI for his permission to present this paper and to the Director of Livestock Research Centre, MARDI for his guidance and encouragement.  The author is also grateful to FAO for sponsorship.

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