Vine lifting
Many sweetpotato varieties are characterized by a growth habit of long vines
creeping over the soil surface. If the soil is moist and the stem touches it,
roots may grow from the nodes. Storage roots may also form at these nodes, but
they are usually small and not marketable.
The principle behind vine lifting is that the water and nutrients supplied to
these roots are therefore wasted, and will reduce the yield of marketable roots.
This waste can be prevented by lifting the vines so that any roots growing at
the nodes break or dry out. Vines should not be turned over because this may
cause rotting of the leaves in contact with the soil.
In practice, the benefit of vine lifting varies with the cultivar and weather
conditions. Cultivars with more upright, bushy habit generally don’t need
lifting, and some trailing types don’t root readily at the nodes. Lifting of
these varieties may be necessary only in prolonged humid conditions.
Lifting is commonly practiced once or twice during a wet season crop, and
often not at all during the dry season. Experiments done by Indonesian farmers
have found that lifting more than once in the season only benefited yield in
very moist conditions. Vine lifting during any season should, therefore, not be
a routine practice, but should be undertaken only after root growth on stem
nodes has been observed. Farmers should look out for root formation on vines
during routine field observations, and then decide whether the labour investment
in vine lifting is worthwhile or not.
Vine harvesting
For many sweetpotato growers, the vines are a valuable source of fodder for
livestock. Vines may be harvested several times during the second half of the
growing season. However, harvesting of vines generally reduces the yield of
storage roots to some extent. The impact on storage root harvest may depend on
the amount of vine removed, the variety, the soil fertility and weather
conditions. Simple experiments can be conducted by farmers to determine the
amount of vine harvesting that provides an optimum balance of vine and storage
root yield.
Vine harvesting usually begins at 30-45 days after planting, when the beds
are covered by vines. Two or three of the longest vines per plant are taken,
leaving about 15 cm length. Subsequently, vines may be harvested every 10-15
days, taking 2-4 vines per plant
References
Rasco,
E.T., Jr. and Amante, V. 2000. Sweetpotato in Tropical Asia. SAPPRAD-PCARRD.
230 p.
van
de Fliert, E. and Braun, A. 1999. Farmer field school for integrated crop
management of sweetpotato. Field guides and technical
manual. International Potato Center. Lima, Peru. 266 p.
Contributed
by:
Vilma Amante and
Jane
O'Sullivan
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