An e-publication by the World Agroforestry Centre
IMPERATA GRASSLAND REHABILITATION USING AGROFORESTRY
4.3 Leguminous cover crops
Leguminous cover crops (LCCs) are planted as a living mulch, to control erosion and keep weeds out. Many species are nutritious forages. When plowed under, they provide large amounts of organic material, nitrogen, and available phosphorus to the soil.
Leguminous cover crops can be used to suppress existing Imperata (Section 4.3.1).
They are most useful to prevent Imperata from growing back after it has been controlled (Section 4.3.2). Legumes are often planted as an intercrop, a relay crop, or a fallow crop.
Dead and dry leguminous vines can burn. At the beginning of the dry season, press the vines and Imperata to make them less flammable. Press the vines even where there is no Imperata. Fire and uncontrolled grazing are important constraints to the use of cover crops.
To suppress Imperata before crops or trees are planted, choose an aggressive species. Use a variety with a short life (for example, Mucuna pruriens var. utilis) if another crop will be planted soon. Use a mixture including species with a longer life (for example, Centrosema or Pueraria) if cover is needed for a longer time. Use a mixture including a drought-tolerant species if there is a distinct dry season. Use good quality seed.
Treatment of leguminous cover crops (LCC)
"Hapi-hapi" in Cebu, Philippines. Farmers in Cebu use this method in /mperaia-infested coconut plantations to improve soil fertility and nut production. They sow 2-3 kg/ ha of Puemria phaseoloides seeds (or the equivalent in pods) and then burn the Imperata to give the Pueraria a quick start. They press after six months and at least once more during the first year. Within two years, the Imperata is controlled and the farmers plant additional crops under the coconuts.
Northern Vietnam. Farmers in upland areas rehabilitate Imperata grasslands by sowing rice bean (Phaseolus carcaratus) in previously burned fields. Two to three crops of edible beans are produced in 1-2 years with hand weeding. Yields are low but the Imperata is suppressed. The bean's leaves are a good fodder. Other crops are then planted, and rice bean is often used as an intercrop with trees, maize, and cassava.
Albay, Philippines. A combination of two varieties of Crotolaria is used for improved fallow. Seeds are broadcast in Imperata grasslands. After at least one year, the Crotolaria is slashed and plowed, and annual or permanent crops are planted.
This is a more intensive strategy for a shorter time period.
Strategy: clear planting sites and grow leguminous cover crop over remaining Imperata.
Leguminous cover crops are most useful as intercrops or relay crops. They shade the soil between rows and occupy the field between cropping seasons, keeping Imperata out.
Protect the food or cash crop from competition with the leguminous cover crop. Choose less aggressive species, or choose species with a short lifespan. Constantly train vines away from trees.
Legume crops that provide food (seeds and pods) are attractive to farmers. They are likely to provide less nitrogen to the soil because nitrogen is concentrated and removed in the seeds.