RA 00048.pdf - OAR@ICRISAT

Cropping Systems with Sorghum
R. W. Willey, M. R. Rao, M. S. Reddy, and M. Natarajan*
At its simplest, a cropping system can be a single
crop, but most farmers grow more than one crop.
In the developing tropics, for example, the farmer
may have to grow several crops to satisfy
different dietary requirements, to spread labor
peaks, or to spread risks caused by the vagaries of
weather, pest attack, or market fluctuations. Thus
a cropping systems approach must recognize that
the farmer often has to optimize returns from a
combination of crops and that the overall productivity
of the whole system is as important as the
productivity of any individual crop.
A major factor determining overall productivity
is the efficiency with which the cropping system
uses the basic growth resources, especially those
that are limiting. This will depend not only on the
efficiency of the individual crops that make up the
system but also on how well these crops complement
each other in time and space. Thus specifically
considering sorghum systems, overall productivity
will depend partly on the efficiency of the
sorghum crop itself and partly on how well
sorghum fits in with other crops.
It is not within the scope of this paper to
discuss the efficiency of the sorghum crop in any
detail, but it is worth noting that compared with
many other crops sorghum is inherently very
efficient. It emerges quickly and produces a
relatively rapid ground cover, is efficient at using
limited amounts of water and nutrients, and has a
C 4 photosynthetic pathway and a high crop growth
rate. This is illustrated by some dry-matter accumulation
and light interception patterns of sorghum
compared with groundnut and pigeonpea
(Fig. 1).
This high efficiency of the sorghum crop sug-
*
Cropping Systems Agronomists, Farming Systems
Research Program, ICRISAT.
gests that complementary resource use between
sorghum and other crops is most likely to occur in
those systems where the peak growing periods of
sorghum and the other crops do not coincide.
Clearly, such temporal differences are achieved
where the other crops are grown as quite separate
ones either before or after sorghum. As will
be seen later, these systems can be very productive
and a major factor contributing to their
success is the availability of short season sorghum
genotypes; in fact, from the cropping
systems viewpoint the importance of these
genotypes lies not so much in their higher yield
potential as in the increased time and opportunity
they provide for other crops. But temporal effects
can also be achieved in intercropping systems
where there is at least some temporal displacement
between sorghum and its associated crops,
and such systems will be discussed in some
detail. It will also be seen that even where
temporal differences do not occur, there are some
intercropping systems where sorghum is able to
complement other crops to achieve better spatial
use of resources.
Types of Cropping System
The cropping systems considered in this paper are
briefly defined here and are then discussed in the
following sections.
Intercropping
This can be defined as the growing of two or more
crops on the same piece of land at the same time.
The sowing or harvesting times of the crops can
differ, but their growing periods overlap. The
essential characteristic of this system compared
with the systems listed below is that there is
competition between the crops.
International Crops Research Institute for the Semi-Arid Tropics. 1982. Sorghum in the Eighties: Proceedings
Symposium on Sorghum, 2-7 Nov 81, Patancheru, A.P., India. Patancheru, A.P. India: ICRISAT.
of the International
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