Gramineae
Bothriochloa pertusa auctt., non (L.) A. Camus, Amphilophis insculpta (A. Rich.) Stapf.
Pinhole grass (South Africa), Creeping bluegrass (Australia), Sweet pitted grass (East Africa).
Panicoideae; Andropogonodae, Andropogoneae, Andropogoninae. There are 35 species occurring in warm regions of the world of which 3 are indigenous to southern Africa.
Occurs throughout Africa and into India and was introduced to Australia as as CPI 2695 in 1931 as Amphilopis (syn. Bothriochloa) glabra (Bisset, 1978).. In South Africa, it is found in arid savanna and bushveld areas, namely Lowveld, Arid Lowveld, Turf Thornveld, Mopani Veld and Sourish Mixed Bushveld (Acocks 1988). It occurs on hillsides, often in overgrazed places.
A perennial, sometimes stoloniferous grass that grows to a height of 1,500 mm tall. The leaf blades are blue-green, 40-300 mm long and 2-8 mm wide. The ligule is a fringed to unfringed membrane. The nodes have a ring of conspicuous white hairs. Inflorescence of spike-like main branches of 3-20 many-jointed digitate or sub-digitate racemes with a purple colour. Inflorescence axis shorter than racemes. The spikelets are in pedicellate/sessile pairs and 4.5-5.0 mm long. The sessile spikelets are hermaphroditic and awnless, the pedicellate ones male-only or sterile. Female fertile spikelets compressed dorsiventrally. Lemmas with 1 awn. Two more or less equal glumes, the lower glumes pitted. The leaves and inflorescences have a strong aromatic smell when crushed.
This species is an average grazing grass (Van Wyk & Van Oudtshoorn 1999). It has good leaf production, but its aromatic smell deters animals. Useful grass for combating soil erosion. In Australia two varieties have been introduced, Hatch (which has become naturalised north of Rockhampton) and Bisset. Bisset provides a good stable ground cover on hill slopes because of its higher ability to withstand frosts and sends out runners that root well (Humphreys & Partridge 1995).
Response to defoliation
Heavy grazing by hippopotamuses leads to dominance of Heteropogon contortus around Lake Edward, Uganda, and still heavier use will lead to poor Sporobolus and Aristida weeds (Heady, 1966).
Grazing management
Graze when the runners are well developed. Trampling by stock will develop the ground cover. Graze well during summer to prevent if from becoming stemmy. In pure stands or with Stylosanthes humilis keep it grazed to 10-15 cm; with siratro let the pasture reach 30 cm (Bisset & Graham, 1978).
Response to fire
Good. An annual burn is necessary if grazing is not heavy.
Suitability for hay and silage
It has been made into hay before the grass becomes stemmy. The hay has been eaten by horses and beef cattle but rejected by dairy cattle (used to better material) and sheep. With siratro its palatability is better. The hay is aromatic.
Value as a standover or deferred feed
It is useful as low quality roughage but is rather stemmy.
Palatability
It is reasonably palatable, much better than Heteropogon contortus, and is improved in association with siratro.
Animal production
Around Rockhampton (rainfall 1 495 mm) on the Tropic of Capricorn, carrying capacity is one animal to 1.2 hectares.
Contains an essential oil with 42 ingredients.
Chromosome base number, x = 10
C4 photosynthetic pathway.
None reported and considered to be non-toxic. Although the scent of the flower heads will not cause taint in milk if eaten, it deters cattle when more palatable feed is available.
A grass which prefers tropical conditions, i.e. moderate to high temperatures, although it is often found in relatively low rainfall conditions (300-600 mm annual rainfall). It is a sub-climax grass that often increases due to disturbance and/or overgrazing. It is a strong competitor and not easily taken over by climax species. It has high seed production and can quickly colonize bare ground. For this reason Acocks considers it to be a caretaker grass since it binds the soil and is not palatable enough to be grazed out of the system (Zacharias 1990).
Altitude range
Sea-level to 2 000 m.
Rainfall requirements
The lower yearly rainfall limit is about 500 mm and its range generally 500-800 mm.
Drought tolerance
It is drought tolerant.
Frost tolerance
Good. It has some winter hardiness.
Response to light
It does not grow well in shade.
Response to photoperiod
It flowers in late April and in November in central Queensland (Bisset & Graham, 1978).
Natural habitat
Open bush and grassland, mainly in heavy textured black soils.
Tolerance to flooding
It will not thrive under waterlogged conditions.
It grows in disturbed places, for example road reserves, but is usually found on fertile soils and often where water collects. It favours moderately drained loam and clay soils and tolerates low nitrogen levels, although it responds well to extra nitrogen (Humphreys & Partridge 1995).
Land preparation for establishment
Establish on a well-prepared seed-bed, or in the ashes of a burn. Oversowing may give reasonable results.
Sowing methods
Surface sow and lightly roll or harrow; broadcast on to a scrub burn; broadcasting into barley stubble and brigalow is effective. In aerial sowing push the seed out of the hopper by hand (Bisset & Graham, 1978).
Sowing depth and cover
Not deeper than 1 cm.
Sowing time and rate
Sow from November to January (summer) at 2 kg/ha. For soil conservation sow at 9 kg/ha. A seed treatment before planting is suggested to remove awns from the seeds which assists sowing; a "de-awner" used for Stylosanthes humilis is successful with B. insculpta seed. However, in South Africa it is reported that Bothriochloa insculpta has fluffy seeds that are very difficult to sow, and therefore it is generally not propagated!
Seed production and harvesting
It flowers twice a year in Rockhampton, Queensland, on the Tropic of Capricorn, in autumn and late spring. For seed the pasture is grazed till late summer and shut till seed ripens in late autumn. The crop is direct headed. Clean seed plots have been established in Queensland to prevent contamination with seed of Dichanthium aristatum (Angleton grass). Seed yield: 10- 30 kg/ha with up to 80 kg/ha per crop with nitrogen fertilizer and irrigation.
Economics
One of the few grasses suited to sowing in black self-mulching clays. It has been used with fair success in reseeding the medium rainfall areas of Baringo, Kenya.
A summer-growing species that flowers anytime from October to June in South Africa; in Australia, Bisset flowers in early May and Hatch in late April.
In a wet season a leaf rust (Puccinia duthiae) can reduce seed yields.
Although it establishes slowly, this grass can quickly become dominant in habitats which it prefers. It is productive and persistent, producing long runners that may root poorly.
Main attributes
Its ability to compete with native grasses on forest country without nitrogen fertilizer and to invade Heteropogon contortus pastures. Its hardiness and ease of establishment.
Main deficiencies
It lacks a little in palatability because of aromatic leaves.
Value for erosion control
It is useful for erosion control on self-mulching black clay slopes. It is one of the few suitable grasses as it establishes quickly and forms a good ground cover. The runners do not take root readily, but this is improved by prolonged wet weather, trampling or by soil cover, and using high seeding rates. The pastures must be grazed or burnt periodically.
Acocks, J.P.H. 1988. Veld types of South Africa (3rd edn.). Mem. Bot. Surv. S. Afr. No 28. Government printer, Pretoria.
Bisset, W.J.1978. The origin of Bothriochloa insculpta cv. Hatch. in Queensland. Trop. Grasslands 12: 208-219.
Bisset, W.J. & Graham, T.G. 1978. Creeping blue grass finds favour. Queensland Agric. J., 104: 245-253.
Gibbs-Russell, G.E., Watson, L., Koekemoer, M., Smook, L. Barker, N.P., Anderson, H.M. & Dallwitz, M.J. 1989. Grasses of southern Africa. Memoirs of the Botanical Survey of South Africa, No. 58, National Botanical Institute, Pretoria.
Heady, H.F. 1966. Influence of grazing on the composition of Themeda triandra grassland. E. Afric. J. Ecol., 54: 704-727.
Humphreys, L.R. & Partridge, I.J. 1995. A Guide to Better Pastures for the Tropics and Subtropics (5th Edn.). NSW Agriculture.
Van Wyk, E. & Van Oudtshoorn, F. 1999. Guide to grasses of southern Africa. Briza Publications, Arcadia, South Africa.
Zacharias, P.J.K. 1990. Acocks' Notes: key grasses of South Africa. Grassland Society of Southern Africa, Howick.