ABSTRACT

Discorca rotundata two underground structures, the fibrous root

systeiit md the thick slouae,e oreans or tubers in which starch is dep.sited. [tic above

rowid part of the yarn plant consists of' v ne-I ke sterns on which leaves and

itilloi'escence are lorined. Due to its vine-like stern, 1). )'OlII/UI(/I(l requires staking lot

optimum development. Vines can grow to great height if provided with a rigid support or

ntav etO\\ verticallyon other herhaceous species. The plant possesses a shallow hhrous

toot systeilt concentrated within the 101) O.3m of the soil; and only very few of' these

fibrous toots penetrate deeper than I m (Onwuerne, 197$).

Yarn is an important staple food in Nigeria. it has ritual and socio-cultural

siituftcancc; it is the 100(1 of choice of nmiiy ceremonies and leslivals and an

indispensable part of bride price (i-lahn ci al. 1987). i)ioscorca ,itu,tdaia, is essentially a

(topical cot) and requires good fertile soil, adequate aiid well distributed autilall and

-ç considerable labour input for agronornie openilions (Njoku, 1963; Onwucrne, 1975;

Okwor, 1990; Ezeh. 1991).

I hictors which influence the condition of the soil are length of fallow, the species

and \'ariet iCS of the crops grown, nioisture .tnd the intensity of the cropping system

(Mutsaers ci al., 1986). Small holder f'arrning systems in South East Nigeria ate

characterized by reduced fallow period of I to 3 years and more intensive cultivation of

kind due to population pressure (Asadu, 1989). Cr01) production is most. commonly on a

subsistence basis and is severely limited by inherent poot soil fertilit. With iticleasitig

population density, the land LISC Irequcntcy increases and fallow phases are very much

shortened. A succession of fallows into secondary forests is in most cases no longer

I lowever. green manure cover crop technology has (lie potential to litiptove the

and productivity 01 the small holder Iariinni systeiii tlii'oueh l)ioloWcal

nitrogen Ii xation and the supply of other nutrients (Carsky ci al; l998 Okpara ci al.,

200 Otcpasa md Njoku, 2001). ideally, crops that need Low nutrient, input are desirable.

1nIoiiuiiateIv, yams do not satisfy this requtrcnienL