NORTH-SOUTH CENTRE - ETH - North-South Centre North-South ...

Understanding yam (Dioscorea spp.)
response to fertiliser application
Yams (Dioscorea spp) are a staple tuber crop for many of
the poorest in Nigeria, Ghana, Togo, Benin, Côte d’Ivoire and
Cameroon. This crop demands a very high soil fertility level
and therefore is usually grown as the first one after longterm
fallowing. Due to the increasing population pressure,
the available areas under long-term fallowing are, however,
rapidly diminishing in these countries. Nevertheless, the
demand for these tubers keeps increasing – also because
of the growing population. Therefore, approaches have to
be developed to fix yams in crop rotations and to increase
their productivity.
tribution pattern respectively. Seminal, adventitious and
tubercular roots were identified. D. alata was shown to be a
shallow-rooting species with coarse and low density roots.
The roots grew in the mound during the vegetative phase,
and mostly horizontally outside of the mound after tuber
initiation. The maximum root extension, with a clump
distribution, was observed at tuber bulking phase. The root
system started to show necrosis during tuber maturation.
Our results suggest that the relatively low root density and
the superficial root system of this cultivar does not limit
tuber yields when water and nutrients are available.
Adequate mineral or organic fertiliser inputs could be
considered to palliate the low soil fertility of cultivated
soils. However, until now, field trials have shown variable
response of yams to mineral fertiliser applications – which
can be positive, null or even negative. We hypothesised
that these variable responses are related to an inefficient
uptake of nutrient derived from the fertiliser itself, which
in turn is related to a limited root density. This study was
undertaken to characterise the root system growth and
its spatial distribution in Dioscorea alata cv. TDa 95/00010
grown in mounds with and without fertiliser application.
Over the growing seasons in 2006 and 2007, the soil
core technique and the wall profile method were used to
determine root growth parameters and root spatial dis-
Research fellow
Valéry Kouamé Hgaza Kouassi, CSRS, Côte d’Ivoire
67
Supervisor
Emmanuel Frossard, ETH Zurich, Switzerland
Collaborators
Aké Sévérin, Université de Cocody, Côte d’Ivoire;
Tié Bi Tra, Ecole Supérieure d’Agronomie, Côte d’Ivoire;
Andres Tschannen and Lucien Diby, CSRS, Côte d’Ivoire
Duration
December 2005 – December 2009
Capacity development
Research fellowships
Root system of yam (Dioscorea spp.) consisting of
adventitious roots originating from the primary nodal
complex and of tuber roots arising from the tuber