Structure of the Production Systems
The development of forage systems was based on the alley cropping system on which a significant amount of research was conducted in West Africa in the early 1980s. According to Kang et al. (1990), the alley cropping system is an agroforestry practice in which woody plants, preferably leguminous trees or shrubs, are grown simultaneously with a crop (Kang et al. 1990). The tree prunings can be used as a green manure to fertilize the companion crop or are fed to livestock. The trees are grown in wide-spaced rows with the crops planted in alleys between the hedgerows. Because of their extensive root system, the trees extract nutrients and moisture from deep soil layers and provide quality forage even during the dry season. When planted on steep slopes, they effectively control soil erosion.
Four production systems were developed that were based on Napier grass intercropped with the tree legumes or the herbaceous legume Clitoria:
(1) Napier grass-Leucaena: Here we present the most important aspects of the system (see Mureithi [1992] and Mureithi et al. [1995] for greater detail of the research that led to development of this system in coastal Kenya). Leucaena hedgerows are spaced 5 m apart and have an intra- row spacing of 25 cm. This gives a plant population of 8000 trees ha-1. Napier grass cv. Bana is planted between Leucaena hedgerows at a spacing of 1 m between rows and 0.5 m within rows. The distance between Napier grass rows and Leucaena hedgerows is 1 m; thus a 5-m wide Leucaena alley can accommodate four rows of Napier grass. Because it does not produce viable seed, Napier grass is propagated vegetatively. Planting is normally carried out at the beginning of the rains, using rooted splits or cane cuttings. The latter are planted at an
angle of 45° to the ground. Leucaena seedlings are raised in a nursery for about 6 weeks before transplanting, when they are about 30 cm high. Leucaena hedgerows can also be established by direct seeding but they are slow to develop.
(2) Napier grass-Gliricidia: In this system, the arrangement for Napier grass and Gliricidia is similar to that of the Napier-Leucaena production system. Gliricidia is propagated vegetatively using cuttings because it is a poor seed producer.
(3) Napier grass-Clitoria: Because of its climbing habit, Clitoria mixes
well with grasses. The method of planting Napier grass is similar to that described above. After planting Napier grass, Clitoria seeds are drilled between rows of the grass at a rate of 3-5 kg ha-1. No seed scarification or inoculation is needed.
(4) Napier grass-Leucaena or Gliricidia-Clitoria: In this system, the arrangement for Napier grass and Leucaena (or Gliricidia) is similar to that used in the Napier-Leucaena production system. After planting both Napier grass and Leucaena (or Gliricidia), Clitoria seeds are drilled between Napier grass rows at the same rate as in the above system (3-5 kg ha-1).