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Digitaria decumbens Stent

Poaceae
Pangola grass, Slenderstem, Transvala digitgrass

Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.


  1. Uses
  2. Folk Medicine
  3. Chemistry
  4. Description
  5. Germplasm
  6. Distribution
  7. Ecology
  8. Cultivation
  9. Harvesting
  10. Yields and Economics
  11. Energy
  12. Biotic Factors
  13. References

Uses

All forms of this grass are excellent pasture grasses, as it remains green and grows throughout alternate wet-dry seasons in the dry Tropics. Forage has outstanding palatability for grazing and harvested forage. Competitiveness of this grass has been used in weed control, in Florida and elsewhere where rotated with vegetable crops. In Hawaii it is used for slope conservation.

Folk Medicine

No data available.

Chemistry

Per 100 g, the forage is reported to contain, on basis, 10.8 g protein, 2.0 g fat, 74.4 g total carbohydrate, 29.8 g fiber, 9.8 g ash, 450 mg Ca. and 350 mg P. According to Gohl (1981), the mean crude protein zero-moisture content of 610 samples of pangola grass was as follows: when fertilized with nitrogen, 13.2%; with rotational grazing, 10.5%; with constant grazing, 5.6%; and ungrazed, 4.9%.

As % of dry matter
DMCPCFAshEENFE
Fresh, early bloom, Trinidad28.68.233.36.92.049.6
Fresh, dough stage, Trinidad39.36.829.57.82.153.8
Fresh, pasture, 10 days' regrowth after grazing, Trinidad14.814.931.011.4 3.039.7
Fresh, pasture, 15 days' regrowth after grazing, Trinidad 20.3 13.7 29.6 10.9 3.542.3
Fresh, pasture, 21 days' regrowth after grazing, Trinidad 21.4 9.2 35.3 12.2 2.3 41.0
Fresh, pasture, 42 days' regrowth after grazing, Trinidad 21.1 4.8 36.3 6.9 1.0 51.0
Hay, 35 days, Venezuela 6.9 34.7 9.8 1.8 46.8
Hay, 45 days, Venezuela 7.5 33.1 9.8 2.3 47.3
Hay, 62 days. Venezuela 5.8 29.6 9.1 2.3 53.2
Standing hay, Trinidad 71.8 3.2 33.5 5.9 1.3 56.1
Silage, Trinidad 27.26.929.9 16.2 2.0 45.0
Source: Gohl, 1981.

Description

Perennial grass, stoloniferous with numerous decumbent stems that root at nodes which touch the ground; culms leafy and only slightly tufted; leaves upright, up to 23.5 cm long; sheaths nearly glabrous; inflorescence many-branched, with many florets, less than .001% producing viable seed; racemes spreading at maturity; spikelets 2.7-3 mm long, glabrous or sparingly silky on the internerves; seed stalks 90 cm or more in height (Reed, 1976).

Germplasm

Reported from the African Center of Diversity, pangola, or cvs thereof, is reported to tolerate aluminum, drought, grazing, heavy soil, insects, low pH, poor soil, salt, sand, shade, slope, trampling, ultraviolet, weeds, and wind. Does not tolerate prolonged waterlogging, alkaline conditions, or copper deficiency. Possibilities of improving pangola grass is by selection of vegetative variation among plants. Most plants now planted have come from a few original sprigs and few important variants have been found. It is believed that pangola grass was produced by hybridization of distantly related species; thus accounting for its sterility. A few variations more recently have shown some promise. 'Pangola grass' was released in Florida in 1945; 'Slenderstem digitgrass' was released in Florida in 1969 and has been planted in several countries. Recently, 'Transvaal digitgrass' a good forage grass resistant to Sting nematode (Belonolaimus longicaudatus) and to Pangola Stunt Virus (PSV), has been introduced to Hawaii, Guam, West Indies, and northern South America. (2n = 30, 27 in 'transvala') (Reed, 1976)

Distribution

Native to South Africa, Transvaal, and similar locatilities. Introduced in United States in 1935 from South Africa. Now, widely distributed and well-established in tropical and subtropical pasture areas, Along Gulf Coast of Mexico, over 400,000 ha are under cultivation (Reed, 1976).

Ecology

Ranging from Warm Temperate Moist (without frost) to Wet through Tropical Dry to Wet Forest Life Zones, pangola grass is reported to tolerate annual precipitation of 6.6 to 41.0 dm (mean of 20 cases = 14.1), annual temperature of 15.9 to 27.8°C (mean of 20 cases = 22.5), and pH of 4.3 to 8.5 (mean of 17 cases = 6.3) (Duke, 1978, 1979; Reed, 1976). Pangola grass tolerates a wide range of soil moisture, pH, and soil fertility. Thrives best when grown in full sun or well-drained moist soils, but good growth can be obtained on soils ranging from sands to heavy clays. It will tolerate light shade and salt spray when planted in coconut groves on beaches. Inadequate rainfall is main factor limiting production range and yield; requires above 63 cm/annum rainfall. Transvala, Pangola, and Slenderstem digitgrasses are all subject to winterkill in Florida (Reed, 1976).

Cultivation

Since Pangola grass and its variations produce almost no seed, it is nearly entirely propagated by stems and crowns, adding to the cost of establishment. Under most conditions, the returns derived from a well-established stand far outweigh the cost of establishment. The grass is easy to establish throughout the year, the probability of survival increased in the wet season. Growth rate and production are reduced during drought, still it is relatively drought tolerant. Mechanized plantings are made on large flat areas, free of boulders. Hand planting is recommended for small areas, stony land, and steep slopes. Pangola grass can be grown pure or in mixtures with tropical legumes, as Centrosema pubescens or Desmodium leiocarpum, in Ghana. Although it is superior to some other warm-season sodgrasses in its competitiveness against wiry and erect forms of herbaceous and woody weeds, it can also be detrimental to herbaceous legumes. Pangola grass shows significant increases in forage yield as result of single annual application of fertilizer, and gives maximum forage production with split applications. In Florida a fertilizer program similar to the following is suggested: a 10-10-10 fertilizer at rate of 560 kg/ha between Oct. 1-Mar. 31; 12-6-6, 450 kg/ha between Apr. 1-May 15; Ammonium sulfate, 170 kg/ha between May 16-Aug. 15; and 12-6-6, 450 kg/ha between Aug. 16-Sept. 30. Green matter yields are increased 50% by addition of 830 kg/ha of 12-6-8 fertilizer, applied in a single annual application as top-dressing. Ammonium sulfate is the most common source of N used on pasture grasses. Pangola grass can be easily eradicated by soil sterilants or non-selective herbicides; or during the dry season by following proper cultural practices. Swine relish the roots, but it is not advisable to use them to eradicate the grass because of the damage they do to soil tilth and texture. Selective grazing causes pangola grass to decrease in a mixed pasture. Long-established grass survives better when the heavy growth has been removed. Pangola grass can be established and makes vigorous growth on sandy soils with pH 4.2-4.5, if it receives a complete fertilizer and necessary minor elements. Liming is recommended, with initial treatment of 2.5 T/ha on newly cleared land with reliming at same rate set at 4-year intervals. Crop also has high ability to withstand heavy trampling by livestock and rapid recovery from overgrazing (Reed, 1976).

Harvesting

Higher annual production of forage is obtained when harvested at 6-week intervals rather than 3-week intervals. Delayed grazing may result in higher production but reduced quality and protein content. Rotational grazing is advantageous to obtain highest yields of quality forage and to maintain adequate stands. When grass is grazed to 10-15 cm, cattle should be moved to a new stand. In Ghana, 5 harvests are made between Mar. 12 and Nov. 16, at 2-month intervals (Reed, 1976).

Yields and Economics

DM yields can be affected by slope. In Taiwan, pangola grass on slopes 10-14deg. bulldozed across the slope yielded 19.2 MT DM/ha, compared to 15.0 MT bulldozed down the slope. On slopes of 14-18°, the yields were 14.9 MT and 9.5 MT/ha. On steeper slopes, yields were 6.3-8.5 MT/ha. Properly fertilized pangola pastures have yielded more than 2.5 MT beef/ha in the West Indies (Hsieh, 1979). Grown in pure stand, pangola grass yields green matter, 16,645 kg/ha, based on 5 cuttings per year, or 3,329 kg/ha per cuttings, the first and second cuttings highest. In mixed stands with Centrosema, 27,853 kg/ha, with average 5,571 kg/ha per cutting; and mixed with Desmodium, 20,041 kg/ha, average 4,508 kg/ha. Yields of 'Transvala', fresh, average 9,982 kg/ha; 'Slenderstem', 6,957 kg/ha; and over a 2-year period, dry matter yields for'Transvala', 55,000 kg/ha; for 'Pangola', 47,000 kg/ha. Invariably, dry matter yields declined from first to fourth harvest but then rose in fifth, suggesting seasonal fluctuation. Most fall-harvested hay is medium to low in protein content, but an application of N 3 weeks before mowing gives increased digestible crude protein and consumption rate of the hay. Its productivity and feeding value make this versatile grass an important forage crop in its area of adaptation, mainly in dry Tropics at lower elevations. Grown in Florida and California, West Indies, northern South America, Hawaii, Guam, Mexico, and West Africa (Ghana). Adapted to other such areas (Reed, 1976).

Energy

According to the phytomass files, annual productivity ranges from 0 to 36 MT/ha (28 in Australia, 7 in Brazil, 2-3 in Colombia, 4-31 in Cuba, 7-12 in Guyana, 18 in Hawaii, 7 in Jamaica, 18-36 in Puerto Rico, 6 in Sarawak, 6-23 in Taiwan, and 0.6 in Venezuela) (Duke, 1981b). Almedia (1981) tabulates data from Cardenas, Tabaso, Mexico, indicating a net annual productivity >43 MT/ha/yr, a gross >51. Daily productivity was tabulated at 11.8 g/m2. Other reported high yields in Digitaria include D. eriantha, 22-45 MT/ha; D. milanjiana, 4-34; D. pentzii, 4-31; D. setivalva, 2-9, D. smutsii, 27-33; D. swazilandensis, 23-35; and D. valida, 5-19. No doubt crab grass could be made into an energy producer instead of an energy consumer, as one of the World's Worst Weeds.

Biotic Factors

Pangola grass is attacked by the following fungi: Mycosphaerella tassina, Piricularia grisea, and Rhizoctonia solani. Pangola stunt virus is a serious disease, transmitted by a delphacid vector, Sogata cifera; however, 'Transvala' is resistant to it. Plants also affected by Potato Virus Y. Nematodes isolated from Pangola grass include: Belonolaimus longicaudatus to which 'Transvala' is resistant, Dolichodorum nigeriensis, Helicotylenchus pseudorobustus, Meloidogyne incognita, Peltamigratus nigeriensis, Rotylenchulus reniformis, and Scutellonema clathricaudatum. Pangola is recommended as a rotation crop on sandy soils infested with cotton root-knot nematode. Insect pests causing severe damage to Pangola grass are Fall armyworm (Spodoptera frugiperda) and Grassworm (Mocis latipes). Yellow sugarcane aphid (Sipha flava), a major pest in Florida, Spittle-bug (Prosapia bicincta), Rhodesgrass scale (Antonia graminis), mole crickets and leafhoppers. Local agriculture agents may have suggestions for control.

References

Complete list of references for Duke, Handbook of Energy Crops
last update July 9, 1996