Page 21 - 17 Cotton SA March 2019

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• Subsidies: Subsidies in farm inputs and soil reclamation, soil conservation, cropping
cotton prices will help farmers to cope with systems, conservation tillage, water-use
the uncertainties of volatile markets. efficiency, nutrient-use efficiency, pest
management, and weed management.
According to Dr Keshav Kranthi, Head In developed countries such as the USA,
of the ICAC’s (International Cotton Advisory Australia and Brazil, plant breeders aim
Committee) Technical Information Section, a to develop cultivars that retain an optimum
change in plant architecture can break yield number of bolls, generally at 15 to 20 bolls
barriers in Africa. He says it would be possible per plant, with a population of 80 000 to
to enhance yields by breeding “compact- 110 000 plants per hectare. However, in
architecture” cultivars coupled with “canopy Africa and Asia, plant breeders traditionally
management”, in which excessive vegetative have been developing plant types that
plant growth is curtailed at a critical stage produced the highest number of bolls (80 to
(either through mechanical methods or with 150) per plant. Agronomists recommended
the use of plant growth regulators) to ensure wider spacing for such varieties to cater to
a proper nutrient source-sink relationship. their potential for tall, wide growth (Figure 1).
Apart from compact architecture, yield Producing more bolls per plant takes a longer
improvement in Africa requires best practices time for higher yields, and if terminated
for plant mapping, canopy management, prematurely, result in low yields.

Figure 1: Illustrating low-density planting* vs high-density planting**.

*Low-density planting, e.g. 90 x 60 cm – **High-density planting, e.g. 76,5 x 8 cm –
India and Africa; with bushy-type plants. Australia, China, Turkey, etc.; with
compact-type plants.

According to Dr Kranthi, plant breeders must therefore seriously consider developing cultivars with
the following plant features:
• Compact, short-statured
• Zero-monopodial
• Short season (140 to 150 days)
• Resistant to sap-sucking insects and local pathogens
• High initial shoot and root vigour
• High ginning out-turn and good quality fibre.

Volume 21 No 1 March 2019 | 21