RA 00048.pdf - OAR@ICRISAT

Ratoon Systems
The importance of ratoon cropping has been
reported in a number of countries (USA—
Plucknett et al. 1970; Worker 1961; Australia
—Parberry 1966; India—Ambastha and Jha
1955; Mandal et al. 1965). Much has been written
on the practical management of ratoon crops but
this paper will deal only with cropping systems
implications.
Considering first of all the system of two
consecutive grain crops (i.e., a "plant" crop and a
"ratoon" crop), the major advantage of ratooning
is that it avoids having to sow the second crop.
This saves on the cost of cultivations and seed, it
reduces labor demands at a critical postharvesting
period, and in the rainfed situation it avoids the
risks associated with sowing the second crop.
Because the ratoon crop gets a particularly rapid
start and also matures earlier than a normal plant
crop, the system also has the advantage of a
shorter total growing period requirement.
The disadvantage of this system, however, is
that the ratoon crop usually produces a lower yield
than a sown crop. At ICRISAT, recent studies
under favorable moisture conditions and over a
wide range of genotypes have given ratoon yields
of about 5 0 - 6 5 % of the plant crops. Thus on yield
considerations alone, the ratoon system is unlikely
to compete where good sequential or relay
systems are viable alternatives. In the rainfed
situation its niche is probably the production of a
low cost "partial" second crop where moisture
conditions are insufficient for a full second crop.
But sorghum's ability to ratoon allows the
possibility of a wide range of other systems
where one or more of the crops are taken for
fodder. In India, systems have been described
where an irrigated fodder crop has been grown in
the summer season and followed by a ratoon
grain crop during the rains; compared with a
normal rainy season crop, the earlier maturing
ratoon crop gives a greater opportunity for traditional
postrainy season crops of cotton (Mandal et
al. 1965; Shanmugasundaram et al. 1967) or
wheat (Pal and Kaushik 1969). A rather different
system is where a rainy season plant crop is cut
for early fodder (about 4 5 - 5 0 days) which then
has the effect of delaying the maturity of a ratoon
grain crop until the drier conditions after the end
of the rains (Sanghi and Rao 1976). The danger of
shoot fly attack is probably the greatest drawback
to these fodder/grain systems.
Where irrigation is possible, systems with two
or three consecutive ratoon crops have been
described (Plucknett et al. 1970; Hussaini and Rao
1966; Rojas 1976).
Rotational Systems
Many of the general principles of rotations, such
as the maintenance of fertility or the control of
soil-borne pests and diseases, are no more
applicable to sorghum than to other crops and this
will not be dealt with here; neither will the special
problem of Striga since this is being covered
elsewhere in this symposium. But one aspect not
covered elsewhere is the depressive effect that
sorghum may have on the yields of following
crops.
Some commonly suggested causes of this
depressive effect are the depletion of nutrients
and moisture, and the locking up of available
nitrogen by microbial action in breaking down the
carbon-rich stubble. But while there is good
evidence that these factors are often involved,
there are instances where fertilizers and irrigation
have not eliminated the effect. The suggestion of
toxic exudates from the sorghum stubble has
always had a mixed reception among scientists,
though recent work has shown very convincing
evidence of excessive production of phenolic acid
that can certainly affect crop growth (Ganry 1979,
personal communication).
But whatever the cause of the effect it has
been reported with a frequency difficult to ignore;
it has been reported in USA, India and Africa, and
on a very wide range of crops (sorghum itself,
wheat, oats, barley, cotton, chickpea, pigeonpea.
and groundnuts). Its effect seems to be greater on
cereals compared with legumes. Thus poorer
wheat yields have been reported after sorghum
than after maize (Myers and Hallsted 1942;
Dunkle and Atkins 1944; Quinby et al. 1958;
Singh and Singh 1966; Laws and Simpson 1959).
especially where wheat has been sown immediately
after the sorghum rather than in the following
year (Myers and Hallsted 1942). or where
rainfall has been low (Laws and Simpson 1959).
Lower cotton yields have been reported after
sorghum compared with pearl millet in South India
(Ayyar and Sundaram 1941), or compared with
fallow or lobia in the Sudan (Burhan and Mansi
1967; Roy and Kardofani 1961). Recent ICRISAT
studies on pigeonpea, chickpea or sorghum
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