RA 00048.pdf - OAR@ICRISAT

Crop Management
M. D. Clegg*
The general methodologies of crop management,
as currently carried out in the various countries of
the world, are extremely variable. This is because
there are many environments with farm sizes
ranging from less than 0.5 hectare (Harwood and
Price 1976) to farm sizes that are in excess of
1000 hectares (Schertz 1979). Regardless of farm
size, the goals of farmers are to produce maximum
crop yields by managing the farming system
so that environmental stresses are minimal to
the growing crop.
According to Zandstra (1977), yield is a function
(f) of management (M) and environment (E):
The symbol M includes the consideration of the
choice of variety, the procedure of plant establishment,
arrangement in time and space, fertilization,
pest control (weeds, insects, and disease) and
harvesting. The symbol E includes the land (soil
characteristics), climate variables (rainfall, daylength,
solar radiation, and temperature) and
economic resources (power, labor and cash).
Throughout this symposium most, if not all, of
these variables will be addressed.
Because crop management encompasses
these many variables this paper will be directed to
various cultural practices or considerations which
have developed in the last decade. Furthermore, it
will be necessary to discuss practices peculiar to
both large farms (high mechanization) and small
farms (little mechanization). In many cases the
principle of the cultural practice will apply to
either.
* Associate Professor, Department of Agronomy, Institute
of Agriculture and Natural Resources, The University
of Nebraska-Lincoln, Lincoln, Nebraska, USA.
Present Considerations
Large Farms
The number of crops grown on large farms are
few. In many instances only one crop is grown
because of the characteristics of the environments.
This results in highly specialized farming.
Variety Selection
New high-yielding hybrids are continuously being
released by commercial seed companies. Resistance
to insects and diseases, seed quality, as well
as climatic stresses are considered in the development
of the new hybrids. Farmers choose hybrids
which are adapted to their areas from these
companies.
Seed of hybrids sold to farmers is processed to
insure a high quality product. Processing includes
sizing, fungicide treating and packaging. Because
seed size varies considerably, the number of
seeds per bag are indicated allowing the farmers
to plant the correct amount of seed per unit area.
A recent innovation is to protect the seedlings
from herbicide damage by the application of a
chemical protectant, which allows the use of
higher concentrations of herbicides for weed
control with less risk of seedling injury (Bumside
et al. 1971; Spontanski and Burnside 1973; Ellis et
al. 1980; Nyffeler et al. 1980; Henken 1981).
Plant Arrangement
Variability of plant height, leaf direction, leaf
number and leaf size exists in grain sorghum.
Proper spatial arrangement is needed for each
genotype in an environment to balance the
radiation load for maximized yields and efficient
water use. With irrigation or favorable environments,
maximum radiation can be intercepted for
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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