The effects of rotation crops and stubble management (including the residual effects of past rotation crops) on soil quality, carbon sequestration, deep drainage, nutrient leaching, yield and profitability of succeeding cotton in irrigated and dryland Vertosols were studied in nine on-station and on-farm experiments located in New South Wales and SE Queensland from 2002 to 2005. Key management issues considered were tillage systems, rotation crops and stubble management systems, and in particular, sowing cotton into standing wheat and vetch stubble.

Soil physical and chemical properties were measured in all experiments. Soil water storage, crop growth, cotton lint yield and fibre quality were also measured. Economic returns in irrigated sites were evaluated by comparing seasonal and cumulative gross margins. Spatial and temporal deep drainage (with the chloride mass balance model) and nutrient leaching, and profile salinity change with an EM38 meter were measured in some NSW sites. Investigations were conducted into cotton crop management practices which could overcome problems associated with sowing cotton into standing (retained) rotation crop stubble.

Residual effects of the rotation crops sown were present up to a period of five years with respect to soil structure, sodicity, exchangeable K, deep drainage and nutrient and salt leaching. Deep drainage, nutrient and salt leaching were generally in the order of ex-cotton-wheat > ex-continuous cotton > ex-cotton-dolichos.

At the dryland site Qld, soil structural properties were affected primarily by tillage system (changing from conventional to zero tillage) with rotation crops affecting structure only during a period of relatively higher compaction. Least compaction occurred with double-cropped cotton-wheat.

In most locations, sowing cotton into standing wheat stubble improved soil organic carbon, rainfall harvesting and gross margins (during the cotton phase of the rotation), decreased sediment concentration in runoff, soil sodicity and salinity; and improved cotton yields and root growth. When cotton prices were low cumulative gross margins with either conventionally-tilled continuous cotton or minimum-tilled cotton-wheat were similar. Irrespective of price, gross margins of minimum-tilled continuous cotton were highest.

Sowing vetch as a rotation crop improved soil physical and chemical properties in good quality soil. In poor quality soil, vetch rotation crops reduced N fertiliser requirements and nitrate-N leaching, but no other soil improvement occurred. Cotton lint yield following vetch was similar to continuous cotton but less than after wheat or wheat followed by vetch. Gross margins of cotton-vetch were always lowest. At lint prices < $450/bale, gross margins of the cotton-wheat (standing stubble)-vetch rotation were highest.

Retaining crop stubble in-situ can cause several problems such as blocking of "gas knives" during injection of anhydrous ammonia as fertiliser and waterlogging during irrigation. In addition vetch regrowth can suffocate emerging cotton seedlings. These problems were overcome by attaching coulter discs to the front bar of the gas rig to cut through crop stubble, removing stubble in furrows at the start of the irrigation season and controlling vetch regrowth through a combination of mechanical methods herbicides.

Drainage was greater where cotton was sown into standing wheat stubble compared with stubble incorporation. Management practices which improved subsoil structure such as permanent beds or cereal rotation crops also resulted in more drainage. Stubble burning increased deep drainage. Yield losses of the order of 50% occurred when soil chloride levels in the 0-60 cm depth at sowing were of the order of 5.3 t/ha.

CSIRO and the Cotton Research and Development Corporation (CRDC) commissioned the Centre for International Economics (CIE) to undertake a benefit cost analysis of the research work done by the CSIRO Cotton Research Unit which was established in 1972. This work included the Unit’s cotton breeding program, as well as its development of several management tools for cotton farmers and their advisers. These tools include SIRATAC which was used from 1984 to 1989, entomoLOGIC which was released in 1994, and more recently, CottonLOGIC. Separate analyses were undertaken for the cotton breeding programs, SIRATAC and entomoLOGIC/CottonLOGIC.

The results show that CSIRO’s cotton research has provided significant economic benefits to the Australian community. Taking CSIRO’s cotton breeding and decision support research as a whole, and assuming a 5 per cent discount rate, the research has returned a present value net benefit of over $5 billion since 1973, with a benefit:cost ratio of 51 and internal rate of return of 31 per cent.

Most of the benefit has come from the cotton breeding programs which have returned net benefits of $4.9 billion in present value, with a benefit:cost ratio of 86 and internal rate of return of 34.

The present value of net benefits from entomoLOGIC/CottonLOGIC were estimated at just over $200 million with a benefit:cost ratio of 18.5. The earlier SIRATAC had a present value of net benefits of $36 million with a benefit:cost ratio of 2.1.

The environmental consequences have not been taken into account. Much of the CSIRO cotton breeding research has been focussed on producing better adapted varieties with better resistance to pest and diseases. The research on management tools has also had a strong focus on this aspect. The result has been a significant reduction in the number of insecticide sprays and use of chemicals on established areas, providing an environmental benefit compared with what would have happened if the original varieties had continued to be used. The new varieties are also at least 11 per cent more water-use efficient. But the CSIRO research has also stimulated the expansion of both irrigated and dryland cotton, which may have meant increased use of insecticides and irrigation water depending on what alternative crops might have been grown in the absence of the research.

In the 2001/02 season Australian cotton growers achieved what is believed to be a world record. They harvested more cotton per hectare than any other major cotton producing nation. This achievement comes with continuing improvement in environmental management. While a favourable season was part of the picture, these improved yields are also an outcome of a comprehensive research program. During the last 30 years the lint yield in Australia has increased by an average of 23 kilograms per hectare per year, one bale per hectare every 10 years or so. The increase is due in part to better plant varieties and in part to improved crop management. The yield improvement is a clear case where a coordinated approach to research delivered the greatest benefits. Dr Greg Constable from CSIRO Plant Industry estimates that plant breeding contributed about 45 per cent of the yield gains, with the other 55 per cent from improved insect control, disease management, plant nutrition and irrigation strategies. Individually these items can have only a limited impact. Packaged together and the Australian industry achieves world records. The move to farming systems approaches means farmers are increasingly examining the interactions between the elements of the production system and the effect they have on cropping outputs. Greater interest in planting trees and establishing wetlands on farms are improving environmental values by providing for greater biodiversity. Other strategies, particularly the Best Management Practices Program, aim to limit negative environmental impacts from cotton production. Each improvement is but a piece in a much larger picture, a picture of a modern agricultural industry maintaining its productivity but not at the cost of its resource base or the environment.

CRDC's Annual Operating Plan for 2011–02 (AOP): the fourth annual operating plan under the CRDC's Strategic R&D Plan 2008–2013.

CRDC's Annual Operating Plan for 2009–10 (AOP): the second annual operating plan under the CRDC's Strategic R&D Plan 2008–2013.

CRDC's Annual Operating Plan for 2008–09 (AOP): the first annual operating plan under the CRDC's Strategic R&D Plan 2008–2013.

CRDC's Annual Operating Plan for 2004–06 (AOP): the second annual operating plan under the CRDC's Strategic R&D Plan 2003–2008.

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Heliothis armigera has been a growing problem for many years, While the cotton producers have borne the brunt of it, reports of increasing damage to crops such as pulses, sorghum an maize have become more frequent. The subtropical climate of the Darling Downs, Burnett and Dawson Callide regions along with the number of host crops grown in the region have created a paradise for Heliothis and devastation for field crop growers. The cotton industry has had avoluntary chemical usage strategy for many years, however, due to many of the same chemicals being used on other crops, chemicals are failing because of the continuous exposure of Henothis to the same chemical in different crops e. g. Carbamates on chickpeas, cotton and mung beans. The last 2 summer seasons have seen many chemicals on the verge of failure as the leve of resistance rose with spray failures occurring when application rates and timing were not 100%. There has been little or no margin for error. In December 1997, Downs growers were warned that cotton may become unviable with years If Heliothis armigera was not managed. In some Downs areas in 1996-97 and again in 1997-98 Heliothis egg lays reached up to 800 per meter with very small and small larvae at to 7 per meter during periods of the season. This pressure meant that many grain crops were also at serious risk i.e all pulse crops and unacceptable damage to sorghum, maize, sunflowers and millets. Added to this list of woes was the poor performance of Ingard cotton. This along with very limited new technology available at a prohibitive price, indicated that a cropping Armageddon was fast approaching