However, locally produced varieties have a limited genetic resource, and introduced
varieties, with years of international plant breeding effort behind them, can very
often grow even better.
HYBRID MAIZE
Because of the maize plant’s habit of bearing the male and female parts separately,
the production of hybrid maize seed on a field scale is relatively simple. The tassels
of the female parent of the hybrid are cut off and removed, so that they cannot self-
pollinate, then pollen from the male parent is taken and introduced to the styles of
the female parent.
The production of hybrid maize seed, using both this method and male-sterile
plant material, is an enormous business that has been hugely successful in increasing
maize yields all around the world. Chemical sterilisation to prevent pollen formation
is not yet 100% effective.
However, as discussed in 1Fc, page 52, hybrid seed can bring its own problems.
Note to the following:
The agronomy of maize is an enormous subject, which has been very thoroughly
discussed in hundreds of books, scientific papers, etc. The following is a brief and
incomplete summary.
PLANTING
Propagation: by seed. In general, earlier planted crops perform better than later
planted ones, provided that there is adequate moisture and the soil temperature has
reached about 12C. It is usually a good idea for food producers to plant at least
some of their maize early—those plants may not only grow better than later planted
ones, but they can be eaten sooner, and so “fill the hungry gap”.
Germination: seedling emergence in moist soil of about 21–30C is 4–5 days; in
12–16 C soils it can take 15 days or more. Maize seed remains viable for 3–5 years
if stored carefully (1O).
Soil: maize adapts to most kinds of soil, from pH 5–8, though like most other crops
it prefers well drained loams of pH 6–7. In alkaline soils there may be symptoms of
iron or manganese deficiencies. It is a heavy feeder, and needs plenty of N, P and K,
Potash probably being the most important major element. It responds well to direct
placement of fertiliser (especially P) next to the seed. But although maize can and
does respond well to fertiliser there are other less expensive and troublesome ways
of increasing maize yields, such as using appropriate varieties, spacing the plants
more sensibly and accurately in the field, and timely planting. Indeed, farmers are
wasting their time, money and effort if they apply fertiliser to maize without first
attending carefully to these factors.
Seed rate: from 10–45 kg/ha or more. In general, rates are higher for hybrids and
early varieties, for early planting and for moist, fertile soils; rates are lower for later,
tall varieties in poor dry soils, as discussed in 1Fb, page 52. For forage maize, about
50,000 seeds/acre are planted.
Seed spacing: this is an important consideration because correct maize plant spacing
can significantly increase yields. Unlike other cereals maize is not good at
°°
°