Urochloa decumbens

Low-growing sward-forming perennial, 30‒45 (‒60) cm deep; culms decumbent or semi-erect, 50–150 cm long, rooting at lower nodes in contact with moist soil; sometimes shortly rhizomatous.  Leaf sheaths tight, terete or somewhat compressed, keeled upwards, more or less finely hirsute; leaves blades narrowly lanceolate, 7‒15 (‒20) mm wide, 5–25 cm long, bright green, moderately hairy; ligule a fringe of hairs.  Inflorescence a panicle comprising (1‒) 2‒5 (‒7) racemes, (1‒) 2‒5 (‒10) cm long borne along one side of a central axis 1‒10 cm long; rachis flat, broadly winged, 1‒1.7 mm wide, minutely pubescent on the front, and ciliate along the edges; racemes almost at right angles to the axis; spikelets borne adaxially in 2 intermeshing but distinct rows on the rachis.  Spikelets elliptic, 4–5 mm long, subacute or acute, falling entire; glumes dissimilar, reaching apex of florets, thinner than fertile lemma;  lower glume ovate, apex obtuse or acute, clasping; 0.33–0.5 length of spikelet, membranous, without keels, 9-veined; upper glume oblong, length of spikelet, membranous, without keels, 7-veined, surface pubescent, apex obtuse or acute. 280,000 seeds per kg.

Similar species

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.

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. 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, 3‒5 mm wide, 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.

Asia: rumput signal (Malaysia); ya siknaentonnon, ya surinam (Thailand)

English: Kenya sheep grass, signal grass, Surinam grass

German: Surinamgras

Latin America: braquiarinha, braquiária, braquiária comum, braquiária de alho, capim braquiária, decumbens (Brazil); braquiaria australiano, braquiaria, decumbens, pasto alambre, pasto amargo, pasto braquiaria, pasto chontalpo, pasto de la palizada, pasto de las orillas, pasto peludo, pasto prodigio, zacate prodigio, zacate Surinam (Spanish)

Native:

Africa: Burundi, Democratic Republic of the Congo, Kenya, Rwanda, Tanzania, Uganda

Cultivated/naturalized:

Asia: Malaysia, Thailand

Australasia/Pacific: Australia, Vanuatu

Caribbean: Cuba, Trinidad

Central America: Costa Rica

South America: Brazil, Colombia, French Guiana, Paraguay, Peru, Venezuela

Forage

Mainly planted for permanent pastures in both grazed and cut-and-carry systems as fresh or conserved feed.  It has been planted as grazed ground cover in plantations. Used in upland rice (Oryza sativa) systems in the Colombian savannas.

Environment

Gives good cover for erosion control on hillsides and for suppression of invasive species such as Chromolaena odorata.

Soil requirements

U. decumbens grows on most soil types except heavy clays, where waterlogging can be a problem.  It is adapted to soils with pH as low as 3.5, being tolerant of high Al saturation and moderately tolerant of Mn, levels of which can be toxic to plants in very acid soils.  It is more tolerant of high Al⁺⁺⁺ than U. ruziziensis as it can detoxify Al in the root system by chelation with citrate and malate.  It does not respond to lime when grown on acid infertile soils, but does respond strongly to improved fertility where deficiencies exist.   The root system of U. decumbens has finer and longer roots than some other Urochloa species, facilitating superior uptake of P and N from the soil.

Moisture

While it will grow in areas with average annual rainfall as low as 700 mm, it is mostly grown in more humid areas with rainfall of 1,200–2,500 mm and higher, with a dry season up to 5 months.  It stays green well into the dry season (better than U. brizantha).  It can tolerate some short-term flooding but not even temporary waterlogging.

Temperature

U. decumbens grows best in temperatures above 19 ºC, so is most productive in the lowland tropics, or during the warmest part of the year in the subtropics or at higher altitudes.  Leaves are burnt off by light frost but the plants recover.

Light

Intermediate tolerance to shade and suitable for ground cover under more open plantations.  It is a common species under mature coconuts (>60% light transmission), but less tolerant of heavy grazing under reduced light than in full sun.

Reproductive development

Nutritive value

Moderately high (similar to other tropical grasses) but greatly dependant on the fertility status of the soil and age of regrowth.  Intermediate to high digestibility (50–80%), chemical composition and intake.  CP ranges from 9 to 20% depending on soil fertility and management, but can decline rapidly with age of leaf, from 10% at 30 days to 5% at 90 days. The inclusion of the legume G. heterocarpa subsp. ovalifolia increased the nitrogen concentration of the grass and the total N yield equivalent to 200 kg/ha N but the legume’s low palatability meant that little legume was eaten.

Palatability/acceptability

Moderately palatable but greatly depending on the fertility status of the soil and age of regrowth.  It is generally rejected by equines.  Livestock reject old or frosted grass .

Toxicity

Young cattle, sheep and goats can develop hepatogenous photosensitization although prevalence appears to be strongly related to environment.  For example, it is of major concern in Brazil and Papua New Guinea but is unheard of in Vanuatu and rare in Australia.  Transferring stock to pasture of different species can alleviate symptoms.  Photosensitization in bovines can be avoided by a rotation of 2 weeks on and 2 weeks off the grass.  Sporadic outbreaks have been related to mycotoxins from the saprophytic fungus Pithomyces chartarum, but also to saponins.  Young, green leaves contain 5–10 times the saponin concentration of mature leaves indicating that U. decumbens pastures are likely to be more toxic during sprouting and early growth.

Feedipedia link

https://www.feedipedia.org/node/489

Dry matter