Limitations on the availability of irrigation water in eastern Australia has created

interest in the possibility of re-establishing cotton in the Oof

NW Australia, where extensive supplies of water are available and there is potentially the

area of Ord Stage II available for development. This project was undertaken to assess what

agronomic management practices may be required for a dry season cotton production system

in the ORIA.

The ability of plants to compensate after insect damage was investigated and

compared to what happens in traditional cotton growing areas of eastern Australia by

removing fruit, tipping out plants and applying a growth inhibitor (mepiquat chloride).

Mepiquat chloride had no effect on the ability of the plant to compensate for fruit loss while

tipping the plant out (removing the mainstem apex) had a negative impact on yield. Plants

that lost fruit later in the growing season were also unable to compensate and were later

maturing than the controls.

Irrigation scheduling experiments concluded that irrigation scheduling should consist

of irrigating every 21 days/125mm pan evaporation between emergence and mid-squaring,

after 110mm of pan evaporation between mid-squaring and cut-out and at least once between

cut-out and defoliation. The use of growth inhibitors such as mepiquat chloride should be

minimised as there appears to be little benefit in terms of lint yield or quality. It is suggested

that it only be considered on early sown (i.e. pre mid-April) crops and on relatively

indeterminant cultivars such as Sicot 289i and their Bollgard II equivalents.

Wet season cover crops appear to have a place in rotation with dry season cotton

production in the ORIA with dwarf pearl millet or sorghum being the prefered crops. This

should be sown at the start of the wet season and sprayed out after approximately 55 days

after sowing to allow time for thecrop to die and stubble to break down. Roundup Ready

cotton also appears to be a possible weed management option, particularly in a minimum

tillage situation where the cotton can be sown into the wet season stubble and weeds

controlled after the crop has emerged.

Fertiliser trials indicate that 80 kg ha-1 of phosphorus is required when sowing cotton

into land that has previously been unfertilised followed by replacement levels in subsequent

years. If fields are left fallow for extended periods of time (i.e. in excess of one dry season)

plants may have difficulty

Cultivars currently recommended for growing on the ORIA are Siokra V-16i and

Sicot 289i and their Bollgard II equivalents. Both have a high yield potential and produce

satisfactory lint quality. However, variety trials have identified several promising lines with

potential for dry season production on the ORIA. In particular, lines derived from Sicala 35i