Urochloa ruziziensis

A tufted, spreading perennial grass forming a dense leafy cover.  Culms decumbent, geniculately ascending, 50–100 cm long, 3–4 mm diameter, arising from short rhizomes, sometimes rooting from lower nodes; fertile culms to 1.5 m high.  Leaf sheath longer than internode, loose, covered with dense tuberculate hairs; ligule a fringe of hairs; leaf-blades lanceolate to oblong lanceolate, contracted at base, tapering to an acute apex, 10–25 cm long, (6–) 11–15 mm wide, upper and lower surfaces densely villose with erect hairs, margins cartilaginous and slightly scabrous.  Inflorescence a panicle comprising  (3–) 5–7 (–9) racemes, 5–10 cm long borne along one side of a central axis (rachis) 4–12 cm long; rachis, broadly winged, foliaceous, triquetrous, 2–3.5 mm wide, ciliate on margins.  Spikelets elliptic, cuspidate, 4–5 mm long, falling entire; glumes dissimilar, reaching apex of florets, thinner than fertile lemma; lower glume oblate, apex obtuse or acute, clasping; 0.33–0.5 length of spikelet, membranous, without keels, 11–13-veined; upper glume oblong, length of spikelet, membranous, without keels, 7-veined, surface pilose, hairy above, apex acute.  170,000–270,000 per kg.

Similar species

U. ruziziensis: culms decumbent, stoloniferous forming a denser cover; racemes (3–) 5–7 (–9), 5–10 cm long; rachis 4–12 cm long, broadly winged, foliaceous, with rounded midrib, 2–3.5 mm wide; spikelets cuspidate, 4–5 mm long, packed in two rows along rachis; lower glume oblate, 11–13 -veined, apex obtuse; upper glume oblong, membranous, 7-veined, surface pilose, hairy above, apex acute.

U. brizantha: culms erect or geniculately ascending, more tufted habit; racemes (1–) 2–16, 4–20 cm long; rachis 3–20 cm long, crescentic in section, narrowly winged, 1 mm wide; spikelets subacute or acute, 4–6 mm long, packed in single row along rachis; lower glume ovate, 7–11-veined, apex obtuse or acute; upper glume oblong, cartilaginous, 7–9-veined, surface glabrous or pubescent, apex obtuse, or acute.

U. decumbens: culms decumbent, stoloniferous forming a denser cover; racemes 2–7, 1–5 cm long; rachis 1–8 cm long, flat, broadly winged, 1–1.7 mm wide; spikelets subacute or acute, 4–5 mm long, packed in 2 rows along rachis; lower glume ovate, 9-veined, apex obtuse or acute; upper glume oblong, membranous, 7-veined, surface pubescent, apex obtuse or acute.

Morphological differences are largely relative or numerically overlapping.

Africa: nyasi Congo (Swahili); itonto (Mosso region, Burundi); ndundwa (Ruzizi plains), lughutaghuta (Kinande, DRC)

Asia: rumput ruzi (Indonesia); ルジグラス  ruji gurasu (Japan); หญ้ารูซี  yaa roo see (ya roo si), หญ้าซูซี  yaa susi (Central Thailand), หญ้าคองโก yaa congo (Thailand); cỏ ruzi (Vietnam)

English: bongo grass, Chinese cabbage, Congo grass, Congo signal grass, Kennedy ruzi, Kennedy ruzigrass, palisade liverseed grass, prostrate signal grass, ruzi, ruzigrass, ruzi grass

European: herbe à Bengali, chiendent de la plaine de la rivière Ruzizi, chiendent du Zaïre (French); niederliegendes Palisadengras (German)

Latin America: braquiária-de-ruzizi, Braquiária-ruziziensis, capim Congo, capim-ruziziensis (Brazil); Congo señal, gambutera (also applied to other Urochloa spp.), Kenia, pasto Congo, pasto ruzi (Spanish)

Forage

Permanent or semi-permanent pasture for grazing or for cutting for green feed and conservation.  Sufficiently shade tolerant to be planted for grazing under coconut.

Environment

Ground cover in coffee.

Soil requirements

U. ruziziensis can be grown on a range of soils providing they are well-drained and of moderate to high fertility.  It is less tolerant of strongly acid conditions than U. brizantha and U. decumbens, and is best adapted to soils with pH between 5.0 and 7.0.  There is some variation among genotypes in tolerance of high aluminum saturation on the exchange complex.

Moisture

Average annual rainfall in the Ruzizi Plain for which U. ruziziensis was named is around 975 mm, over 4 seasons: the long dry season (June–August), the short wet season (September–November), the short dry season (December–January), and the long wet season (February–May).  It has proven well-adapted to conditions in N Thailand where the annual rainfall average is 1,000 mm, with a wet season from May to October and a distinct dry season from Novermber to April.  It has also grown well in parts of the humid tropics with annual rainfall of 3,000–3,500 mm.  In general, it can perennate in areas with a dry season up to 4 months, and behave as a regenerating annual under extended dry conditions.  It has poor tolerance of flooding, and does not persist on poorly-drained soils.

Temperature

The altitude of its area of origin in the Lake Edward and Lake Kivu districts of Rwanda, Burundi and the Ruzizi plains in DRC ranges from 750 to 1,500 m asl at latitude about 3° S.  Average annual temperature is about 24 ºC.  While U. ruziziensis is best adapted to the warm lowland tropics, it has been grown successfully up to 2,000 m asl.  Optimum growth occurs at 33/28 ºC day/night, and it exhibits little growth below a night temperature of 19 ºC.  It is killed by heavy frost and regrowth is very slow after light frosts.

Light

Ruzi has moderate shade tolerance and is grown under coconut plantations.

Reproductive development

While U. ruziziensis exhibits a quantitative short day flowering response, there is considerable variation in flowering time among genotypes within the species, from late summer to mid-autumn in southern Brazil (Campo Grande, Mato Grosso do Sul, 20.5° S).  Ruzi grass flowers in mid-autumn in northern Australia (South Johnstone, Queensland, 17.5° S) and October to November, with peak flowering near the end of October in N Thailand (Chiang Mai, 18.8° N).  Unlike U. decumbens, an apomict, both diploid and tetraploid forms of U. ruziziensis reproduce sexually.

Defoliation

It can stand moderately heavy grazing and requires high levels of fertilizing to persist under frequent cutting.

Fire

Ruzi is sensitive to fire, and recovery after fire is slow.

Guidelines for establishment and management of sown forages.

Establishment

Ruzi grass seed needs to be stored for at least 6 months after harvest to overcome dormancy, but quality deteriorates if seed is kept too long at high temperatures and high humidity.  Seed can be treated with concentrated sulfuric acid for 15 minutes to break dormancy, but this poses dangers to the operator and to the seed if left too long in the acid or not washed thoroughly after treatment.  Seed is normally sown at 2.5–10 kg/ha (depending on seed quality) onto a well-prepared seedbed and lightly covered, no deeper than 2 cm.  Seedlings grow vigorously.  Ruzi grass can also be established vegetatively using stem cuttings with rooting nodes.

Fertilizer

Ruzi demands high soil fertility.  Nutrient deficiencies, primarily P and K, should be corrected prior to planting, adequate maintenance fertilizer, particularly N, should be used to maintain productivity under grazing or cutting.

Compatibility (with other species)

While ruzi grass forms a dense cover and competes with weeds under light grazing, the sward opens under heavier grazing, allowing broad-leaf weeds to establish.  It will combine with a range of twining, erect and shrub legumes.

Companion species

Grasses: not normally sown with other grasses.

Legumes: Centrosema molle, Desmodium intortum, Desmodium uncinatum, Leucaena leucocephala, Stylosanthes guianensis var. guianensis.

Pests and diseases

Ruzi is severely attacked by spittlebug (Aeneolamia, Deois, Mahanarva, Zulia spp.; Hemiptera: Cercopidae) in tropical America.  Nymphs and adults damage the host plant by sucking its sap and injecting a toxin, that initiates yellowing and death of the forage, making it unpalatable for cattle.  Leaf is attacked by foliar blight (Rhizoctonia solani) in tropical America.  Seed heads are attacked by an ergot fungus (Sphacelia/Claviceps) in DRC.

Ability to spread

Ruzi spreads relatively slowly in existing vegetation by stolons and seed drop.  Spread is more rapid where a clean seedbed is provided and soil fertility is sufficiently high.

Weed potential

Unlikely to become a weed of importance due to its relatively slow spread and high fertility requirements, but has potential to become a minor weed.

Nutritive value

Dry matter