Gliricidia sepium, commonly known as gliricidia, is a nitrogen-fixing tree, native to central America and the United States.
However, due to its many uses and fast growth, it is widely cultivated in many tropical and subtropical regions, including Africa, India and Southeast Asia.
According to the Guide To Tree Planting in Kenya, a publication of the Kenya Forestry Research Institute (Kefri), it grows in ecological zones whose altitude ranges from 0 to 1,600 metres above sea level.
Ideal temperatures are 20 to 30 degrees centigrade and annual rainfalls of 600 to 3,500mm. In Kenya, it also does well in dry regions.
Benefits
The tree’s Latin name means “rat-killer” because its leaves contain poison which kills rats, moles, mice and other rodents as well as non-ruminants like pigs, donkeys and horses.
The tree is also used for firewood, charcoal, poles, fodder (leaves, pods, seeds and shoots), bee forage, shade, mulch, soil conservation, windbreak and live fence. Its wood is resistant to termites because of its poison.
Studies show gliciridia fodder contains more than 20 per cent crude protein. It is readily palatable for ruminants like cattle, sheep and goats. However, as already stated, it is poisonous to non-ruminants.
One of its most important benefits is its ability to improve soil, being both a nitrogen-fixer and recycler of nutrients. It increases soil fertility, boosting crop yields almost three times without any chemical fertiliser application.
This is especially in impoverished soils where yields are very low.
One study that focused on the tree’s ability to boost food production was carried out by Ajayi OC, Place F, Akinnifesi FK and Sileshi GW in 2011. Titled ‘Agricultural success from Africa: The case of fertiliser tree systems in southern Africa (Malawi, Tanzania, Mozambique, Zambia and Zimbabwe)’ and published in the International Journal of Agricultural Sustainability, it revealed that the tree can boost maize yields per hectare by up to 300 per cent.
Another study, ‘The long-term effects of gliricidia–maize intercropping system in southern Malawi’ by Makumba W, Janssen B, Oenema O, Akinnifesi FK, Mweta D and Kwesiga F. published in the journal Agriculture, Ecosystems and Environment, arrived at similar findings.
Indeed, these trees are a key reason Malawi has become a major maize exporter.
It is deep-rooted with limited lateral root growth, which lessens competition for water and nutrients with food crops.
In addition, it has the ability to pull up nutrients from far beneath the ground into a crops’ root zone, making it one of the best agroforestry trees for intercropping.
Its green manure may contain as much as 4 per cent nitrogen. Other valuable nutrients the leaves add to the soil are phosphorus, potassium, calcium and magnesium.
Gliricidia is a good source of bee forage for honey production and controls striga, the parasitic weed that affects cereal crops like maize, sorghum and millet.
It improves water infiltration, thus reducing run-off and soil erosion. It also reduces pollution because the use of chemical fertilisers and sprays can be minimised.
Propagation
Gliricidia is best propagated from seeds. Stem cuttings can also be used but they do not give very good establishment rates.
Gliricidia seeds can be directly planted in well-prepared land or nurseries for six to eight weeks before transplanting.
Seeds sell at Sh4,000 a kilogramme at Kefri shops.
For uniform germination, Kefri’s Seed Handbook of Kenya recommends soaking seeds in hot water for 12 hours.
They can then be sown in the bed or directly into the field during rainy seasons. Ensure you cover the seeds with light or thin soil and dry mulch.
Watered regularly, the seeds will germinate within seven to 14 days of sowing.
The spacing varies with your purpose of planting the tree.
For intercropping and management of soil fertility, the ideal spacing is four metres between gliricidia rows and a metre within rows.
If you want to establish a forest of only gliricidia, spacing of one metre or less is recommended.
Management
Gliricidia is managed by pruning or what is also known as pollarding or coppicing.
This is done at 1.5–2m above ground 18–24 months after planting.
In subsequent growing seasons, the trees can be pruned every two to three months. The pruned branches are used as firewood and the leaves as green manure.
The trees mature between 15 and 20 years.
Mr Wanyonyi is managing partner at Storylines Kenya.
