Agronomic Factors High On Cotton Agenda

03 December, 2002

___While starting soil moisture and a regular replenishment of moisture in the soil profile are key elements in dryland cotton production, soil nutrient availability, weed control and vegetative growth management are also vital elements, according to CSD extension and development agronomist, John Marshall._

Addressing 150 growers at a series of Dryland Cotton Options meetings in north west NSW and on the Downs, John Marshall said surface and deep sampling for nitrogen availability were prerequisites to determining in-crop nitrogen needs.

“Soil tests to 60cm for N, together with allowances for in-crop mineralisation, helps determine whether N fertiliser will be required to achieve maximum yield potential,” John Marshall said.

Noting that skip row dryland cotton was particularly slow to compete with early weeds, and that the performance of surface applied residuals was often unreliable in dryland, being highly dependent on subsequent rainfall patterns, John Marshall said the use of well setup shielded sprayers was critical to countering weed problems.

He said trends in the United States, where it is estimated that 75 per cent of the area planted to cotton next season will be in the form of Roundup Ready varieties, suggests the Roundup Ready technology will be readibly accepted in Australia, when that technology receives approval (approval and pricing decisions imminent). It has a particular fit in dryland cotton where no-till production techniques are very popular.

In relation to controlling vegetative growth, Mr Marshall said Pix use in dryland cotton needs to be handled very carefully as plant stress can occur much more rapidly under this system. However, it may be needed if early fruit retention is poor, below 50 per cent.

Pix may also be required if deep soil tests show liberal supplies of nitrogen below 60cm, because under favourable conditions later in the season, the crop can tap into these deep supplies, boosting vegetative growth. In all cases, however, crop growth monitoring looking at node length around first flower should be undertaken.

He suggested that if initial soil tests show high nitrogen levels in fields, these fields should be planted first.

Commenting on row configurations, he said there were pros and cons to using skip row. However, in what promises to be an average year, its use could maintain yields, assist fibre length, offer wider weed control options, and facilitate savings in seed, planting time, starter fertiliser, insecticides, defoliants, and picking.

But skip row configurations could also reduce maximum yield potential, and make weed control more critical. Good establishment was also essential, and bush size could also be more difficult to control.

Further Information: *"Robert Eveleigh**, John Marshall, Greg Kauter or Craig McDonald":showstaff.asp?staff=1