Agriculture Reference
In-Depth Information
of the intercrop are the supply of nutrient-bearing leaf biomass directly to the soil,
with no land displaced from food crops. One disadvantage is the difficulty of till-
ing the soil near the tree because of woody tree roots. Coppicing species may be
planted in hedgerows for alley cropping where precipitation is ample and the hedge-
rows of trees will not compete with the cereal crop for moisture (Sanchez 1995).
Noncoppicing species, such as
Tephrosia
(
Tephrosia vogelii
),
Sesbania
, and
Acacia
angustissima
are planted in 2-year improved fallows, to enrich the soil before 2-3
years of maize cropping. Improved fallows also provide N-rich leaf matter directly to
the farmed soil. Although cereal grain yields after the improved fallow usually more
than repay the time lost to fallow, the most food-insecure farmers may not be able to
take the land out of production to take advantage of the benefits.
Fast-growing native and nonnative species have been selected by ICRAF (2013)
and by national agricultural research services (Snapp et al. 2002) to provide rapid
rehabilitation of soils.
Tephrosia vogelii
has often been used in improved fallows,
and is a common shrub in eastern and southern Africa. A more productive cultivar,
formerly called
Tephrosia candida
, was selected in India from the original
T. vogelii
germplasm, and has been introduced into eastern and southern Africa.
Gliricidia
was brought as an intercropping species from central America (ICRAF 2013) to
eastern and southern Africa.
Tephrosia
and
Gliricidia
are fast-developing species
that quickly produce nutrient-rich leaf biomass for soil fertility improvement.
In silvopastoral agroforestry (Figure 11.3), trees are either planted or protected
among naturally regenerating populations, and are left scattered in grazing land to
increase the carrying capacity of the grazing system (Hadgu et al. 2009). In some
areas with high population density and rainfall, agroforestry forage species are
planted in fodder banks, and the vegetation is cut and carried to confined livestock
(Figure 11.4), especially dairy stock (Chakeredza et al. 2007).
FIGURE 11.3
Silvopastoral agroforestry near Shinyanga, Tanzania. (From Constance
Neely, Charlie Pye/ICRAF.)
