Cocv~tfyand network repoWRapports nafiunauxet du r&eau 291
State have as many as 404 p e r s o n h " m e pressure on agricultural land is so high
that the original forest vegetation has been removed in most places leaving wild oil palrns and secondary vegetation. Shifting cultivation witb long fallow periods was the dominant h h g practice until some 3 4 decades ago. At that time, land-use intensity consisted of 10-12 years of fallow to regenerate soil fer&ility,but today, fallow periods hardly exceed 3-4 years. The obvious result of this mustainable land-use system is soil degradation and soil erosion. Soil fertility is poor and the soil is acid (pH = 3.8-5.2). Some yam landraces have become extiuct because the soil no longer provides the type of fertility they require. The major starch staple now is cassava, which tolerates marginal soils. That is why the major research h t in this zone is soil fertility regeneration and improved land-use systems. The use of organic fertilizers is being emphasized such as the use ofIe,@minous cover crops, shrubs, and trees for soil: fertility regeneration as welt as multistrata cropping systems that ensure complete soil cover to control erosion and reduce weeds.
Cover crop workers in southeastern Nigeria At the end of 1998, the active cover crop workers were as follows: Dr J.E.G. keorgu, Agronomist, NRCFU, Umudike - Evaluation of leguminouscover crops for soil fertility regeneration and weed suppression in the degraded forests of SE Nigeria. - CCropnet Trial title& Evaluation of the suitability oftwo Mumnu varieties for soil:fertility regeneration and weed suppression in the degraded forest ecology of SE Nigeria. Dr A.O. Ano, Soil Scientist, NRCRI, Umudike Evaluation of the contribution of leguminous and cover crops to the conservation of the soil resource base and the productivity of cassava-based cropping systems - EiTect of vegetablecowpea population on the conservation of the soil resource base and seed yam yield in yam minisettlcowpea intercrop. Dr DA. Okpara (Federal University of Agricdtwe, Umudike), M i J..Njoku (NRCRI, Umudike) and ProE J.E. Aslegbu (University of Nigeria, Nsukka, Agronomists) Studies on cover crops in the lowland humid forest zone of SE Nigeria Growth and yield response of four mabe varieties to green manure sources - Response of two sweet potato varieties to green manure sources - Evaluation of the duration ofMumna fallow on growth and yield ofmaize - Effects of duration of Mucma fdlow on growth and yield'of two varieties of sweet potato
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