Stylosanthes macrocephala (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Stylosanthes macrocephala M.B. Ferreira & N.M. Sousa Costa

Protologue: An. Soc. Bot. Brazil 28 Congr. Nac. Bot.: 87 (1978).

Family: Leguminosae

Chromosome number: 2n= 20?

Origin and geographic distribution

S. macrocephala originates in South America; its natural distribution is restricted to sub-humid and dryland areas of central and eastern Brazil. Experimental lines have spread for testing to other tropical regions, including South-East Asia.

Uses

The main use of S. macrocephala is as forage in permanent pastures grazed by ruminants.

Properties

In many regards, S. macrocephala is similar to S. capitata Vogel. Its nutritive value, however, is higher: in 6-week-old regrowth, N concentrations in leaves range from 2.2% - 3.5% (stems: 1.4-1.8%), and leaf DM digestibility from 66% - 75% (stems: 46-61%); P concentrations are moderate to low, 0.17-0.25% in leaves and 0.13-0.25% in stems. There are about 500 seeds (dehulled pods)/g.

Botany

A perennial, fine-stemmed, many-branched, and taprooted subshrub, prostrate to semi-erect, 20-80 cm tall; stems and branches hairy-bristly. Leaves 3-foliolate; stipules obovate, 14-16 mm × 5-6 mm, with pointed teeth, pubescent to glabrous or bristly, with 11-13 pairs of veins; petiole 1-2 mm long, villous; leaflets lanceolate, 20-55 mm × 10-19 mm, pubescent or glabrous, with 7-10 pairs of veins. Inflorescence a capitate spike, terminal or axillary, ovoid to almost spherical, 14-18 mm × 10-15 mm, with 10-30 flowers; often several inflorescences in a cluster; bracts imbricate, 1-foliate, elliptical-ovate, 10-12 mm × 8-9 mm, pubescent, with 11-15 veins, reddish; flowers papilionaceous, small, with obovoid standard 4-6 mm long, yellow, striated; axis rudiment and 2 inner bracteoles present. Fruit 2-articulated, reticulately nerved; both articles usually fertile; the upper one glabrous, 3-4 mm × 2.5-3 mm, with a short, straight to uncinate beak; lower article villous and smaller. Seed yellow-brown, sometimes slightly mottled, to black.

Like S. capitata , S. macrocephala persists through extensive seedling recruitment. It is a prolific seeder. Cultivar "Pioneiro" has been released in Brazil for use in the Cerrados savanna region.

Prior to its relatively recent description, S. macrocephala has sometimes been referred to as S. capitata or S. bracteata Vogel.

Ecology

S. macrocephala has essentially the same climatic and soil adaptation as S. capitata . That is, good adaptation to savanna environments, mainly in terms of tolerance of the prevailing acid, low-fertility oxisols and ultisols.

Agronomy

The agronomy of S. macrocephala is similar to that of S. capitata . Newly harvested seed may have to be treated to reduce hard-seededness. Although S. macrocephala nodulates effectively with native rhizobia, inoculation with an effective strain of Bradyrhizobium is recommended. Although tolerant of low fertility, productivity is enhanced by fertilization. It is somewhat less productive than S. capitata , during both the rainy and dry seasons. Seed set and seedling recruitment are essential for long-term persistence. S. macrocephala is, in general, more anthracnose-tolerant than any other Stylosanthes species. In Colombia, it can be seriously affected by Rhizoctonia foliar blight.

Genetic resources and breeding

A large and quite variable S. macrocephala collection is held at CIAT (Colombia). At present there is no breeding programme for S. macrocephala .

Prospects

Unless more productive cultivars with better dry-season performance become available, the potential role of S. macrocephala for pasture development in its particular ecological niche will most likely be limited, as S. capitata is an equally well-adapted but more productive species.

Literature

• Schultze-Kraft, R., Costa, N.M.S. & Flores, A., 1984. Stylosanthes macrocephala M.B. Ferr. et S. Costa - collection and preliminary evaluation of a new tropical pasture legume. Tropical Agriculture (Trinidad) 61: 230-240.
• Stace, H.M. & Edye, L.A. (Editors), 1984. The biology and agronomy of Stylosanthes. Academic Press, Sydney, Australia. 636 pp.
• Thomas, D. & Grof, B., 1986. Some pasture species for the tropical savannas of South America. I. Species of Stylosanthes. Herbage Abstracts 56: 445-454.

Authors

R. Schultze-Kraft