Dryland cotton fanning systems are complex and usually comprise of a number of different rotational crops in conjunction with summer and winter fallows. The standard system employed in dryland cotton production is the planting of cotton after a 10-month fallow from a winter cereal(Marshall 2002). However, there are a number of alternative planting options, such as sorghum, sunflowers or Innize, which for reasons of price or available soil moisture should be planted in place of cotton. Although originating from hot and regions and tolerant of long dry periods, modern cotton varieties require warm to hot growing conditions and reliable rainfall during the growing season. Cotton should be planted into a minimum of 60cm of wet soil, where as in lower rainfall areas 90cm of wet soil is preferred to provide sufficient moisture between rainfall events (Bange et al. 2002). For these reasons, dryland cotton production tends to be limited to areas receiving greater than 600mm of rainfall annually, with approximately 40% of that rain falling during the summer growing season. Currently, cotton is grown commercially from Hillston in the south-west of NSW to Emerald in central Queensland, although trial plantings have been established in the Northern Territory and the northwest regions of Western Australia. Dryland production accounts for approximately 20% of the total area planted to cotton, with the junior production regions in the lower and upper Namoi Valley, Moree, the Darling Downs, south-west Queensland and central Queensland (Marshall et al. 2002).

Adequate soil moisture and the likelihood of receiving planting rains are critical factors for growers in deciding which crops they are likely to plant, particularly in the summer cropping phase. The critical nature of soil moisture to dryland production has seen the evolution of a number of different planting configurations, including solid, single skip row and double skip row planting that maybe employed by growers to conserve soil moisture throughout the season.

Weed management in farming systems involving dryland cotton is then by nature equally complex. A number of the residual herbicides used in rotational crops may damage cotton, in particular the sulfonylurea and triazine herbicides such as chlorsulfuron and atrazine. Equally, a number of the common cotton herbicides have long plant backs to either winter cereals or other summer cereals used in rotation with dryland cotton. To preserve soil moisture, many dryland growers have adopted minimum or zero tillage systems that are almost solely reliant on herbicides for weed control . Control measures therefore must be flexible to allow last minute changes in the crops grown due to soil moisture limitations or price fluctuations and need to provide adequate levels of protection against weeds in the chosen crop, as well as in the planting configuration being used.

To better understand the weed management issues of this complex farming system and to provide direction for future research efforts, a scoping study was initiated in July 2001 by the Cotton Research and Development Corporation (CRDC), Australian Cotton CRC, Grains Research and Development Corporation (GRDC) and CRC for Australian Weed Management. The scoping study was a collaborative project involving scientists and technical staff from Queensland Department of Primary Industries and New South Wales Agriculture.