Introduction
Forage legumes are important in agricultural intensification (Tarawali et al., 2001) because they provide herbage for livestock, grains for humans, green manure to the soil, nitrogen to both companion and subsequent crops through legume fallows. Increased usage of forage legumes in the tropics and sub-tropics is inevitable because of limited supply and high cost of in-organic nitrogen fertilizer including the serious protein deficiency problems among human and animal populations (Hoveland, 1986). Forage legumes which are synonymously referred to as cover crops are reputed to be the backbone of sustainable annual cropping systems (Sullivan, 2012). Their use is very relevant in the humid tropics where high rainfall rapidly depletes soil nutrients especially nitrogen. They also replenish soil-organic matter content while suppressing weeds. Forage legumes accumulated 144 kg ha-1 N, 18 kg ha-1 P and 140 kg ha-1 K after 4 months of re-growth (Muhr et al., 1999).
In an effort to incorporate forge legumes into the local cropping system of different regions, several screening trials were conducted. Examples are in semi-arid Zimbabwe (Jingura et al., 2001), in the moist savannah of Ghana (Barnes, 1996), in sub-humid Nigeria (Odunze et al., 2004), in highland Cameroun (Pamo and Mubeteneh, 1995), in moist savanna of Nigeria (Abayomi et al., 2001) and in sub-humid south-West Nigeria (Muhr et al., 1999).
Justification for the Study
Research is needed to ascertain which forage legumes are adapted to the humid rainforest region of Nigeria. Moreover, it is apparent that no comprehensive evaluation of forage legumes has been carried out in the humid rainforest of Nigeria. Furthermore, it was reported that the performance of forage legume in terms of herbage and crude protein yields is influenced by location (Muhr et al., 1999). The use of forage legumes in the humid rainforest of Nigeria will increase because commercial livestock production has increased in the region. There are now more non-trypanotolerant breeds of beef cattle such as white Fulani, Zebu (ILCA, 1990) and trypanotolerant breeds such as Muturu and Ndama cattle in the region. These animals require protein rich forage legume herbage to supplement their feeding.
Consequently, this research was carried out in the humid rainforest region of Edo State, Nigeria with a specific objective,
Objective of the Study
To evaluate the performance of seven herbaceous forage legumes in terms of growth and herbage yield.
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