Balanced fertilisation of major plant nutrients, nitrogen, phosphorus and potassium is a prerequisite for optimum growth and development of any crop including cotton. Interaction between nitrogen and phosphorus has been reported widely. For example, increasing level of N might influence the efficiency and uptake of P, and vice-versa. Similarly, optimum potassium nutrition for boll retention and boll loading is critical for cotton. Although Hearn (1975) and S. Yeats (1997; personal communication) conducted field experiments for optimising N levels, there has been no work involving all the three major nutrients for cotton production in the Ord. Our work reports results from a preliminary study conducted in 1999 on yield and quality of cotton in response to N, P and K fertilisation

In the Namoi valley a pilot project has trialled exciting new ways to engage growers and their families in managing natural vegetation on their farms under best practise. Engagement has focused on families using existing social networks and has proven to be very successful.

In the irrigated cotton-growing areas of south eastern Australia, there is an increasing awareness for the need for land resource information and its importance for environmental management. This is particularly the case at the field scale where soil management is highly desirable. Acquisition of soil information at this level is labour intensive and time consuming, however. A major problem is determining where samples should be taken. What is required is a relatively cheap and efficient technique, based on remotely sensed data, which can be used as a surrogate for soil survey and therefore assist with the selection of suitable sampling sites to account for the various soil types and spatial variability of soil properties.

Can knowledge of climatic conditions and associated rainfall variability at time scales of several seasons to decades be used to improve cropping systems managementΓ This is a question at the core of this GRDC/CRDC funded research project. There have been many examples where farming practices in Australia were originally developed during periods of above-average rainfall. Research has found that in later decades there were periods when reliable rainfall patterns did not persist. In some cases this led to environmental degradation, a rapid decline in productivity, and increased farm abandonment, all of which have been at a great cost to individuals and the nation as a whole (McKeon et al 1990). Obviously, management strategies that have been developed during periods of low rainfall might not be appropriate during times of higher rainfall. Understanding such climatic cycles might provide an opportunity to put historical experiences into perspective and to choose management strategies that are appropriate for current climatic conditions

The application of cotton defoliants has on occasions been observed to effect the growth of native trees. Cotton growers need to know the potential effects of the defoliants on native trees in their local environment. They also need to know the implications of defoliant drift onto their spray drift buffer strips, which growers have spent many hours and dollars establishing on their farms. Spray drift from cotton defoliant chemicals has also been suggested as a potential causal agent of native tree dieback in the Liverpool Plains region of NSW and greater north-west NSW. Native tree dieback can be caused by many factors and the causal agents have not been effectively identified or justified, although many hypotheses have been formulated. Such causal theories include insect and bird attack, root pathogens such as Phytophthora cinnamomi, mistletoes, poor seedling recruitment, dryland salinity, grazing, old age, drought and waterlogging. The primary aim of this study was to determine whether cotton defoliants affect native tree species common to north-west NSW and to quantify any impacts.

Polymeria take-all is a native Australian plant which is particularly troublesome throughout the Australian cotton industry because it is difficult to control. For example, shallow chipping once per month for four months increased the dry weight production of Polymeria take-all shoots but not cotton production. Again, single applications of glyphosate and Starane, while decreasing the shoot growth of Polymeria take-all, did not increase cotton yields. In contrast, repeated severe defoliation performed under non-irrigated conditions reduced the growth of shoots and rhizomes of Polymeria take-all in an uncultivated area trial. These results have been used to help develop best management practices for Polymeria take all control which will include prevention, herbicide application, cultivation and field hygiene

Soil fertility is the most important soil quality indicator that needs to be measured and monitored. Through human history, decline in soil quality in general, and fertility in particular (due to neglect) had led to the demise of Great Empires. Recently, soil quality and its importance has received extensive attention due to environmental concerns. Soil quality has now formed the basis for the development of sustainable agriculture, and indeed it could be used for evaluating and judging the sustainability of soil management practices and land use systems (Wang and Gong, 1998). Soil fertility can be defined as the capacity of the soil to supply nutrients and provide other physical and chemical conditions for optimal crop growth. Soil fertility, therefore, is a subset of soil quality, which defines the overall fertility and the soils capacity to sustain crop production, provide good conditions for soil organisms, imbibes and ameliorate environmental pollution and resist degradation (Larson and Pierce, 1994). The focus of tints paper is on the analysis of chemical fertility and its versatility and distribution patterns in the lower Namoi Valley. In doing so, we emphasize the basic soil(chemical) fertility and its generality and are not specific to any particular crop. The principle is, however, relevant to the dominant crops grown in the area, namely: cotton, wheat and sorghum.

The use of natural (non-synthetic) chemicals to influence insect behaviour is likely to be well known, in one way or another. Those troubled by mosquitoes are likely to have tested the hypothesis that citronella oil-based candles are repellent to mosquitoes, with varying degrees of success. Those who have tried to control fruit-flies may well have tried protein bait traps whose "scent" lures flies to a pesticide-containing solution, and so to their deaths; the attractant, to which both males and females respond, is a complex mixture of chemicals derived from the breakdown of the protein - commonly brewers yeast. Another "natural" fruit fly attractant is a single chemical, methyl eugenol, a component of many flower fragrances. Only the males of many fruit fly species find it attractive, and it is used in monitoring and control programs

In the Australian cotton industry nutrition is a significant cost with 75% of irrigated cotton respondents to the 2012-13 grower practice survey spending between $300 and $600 per hectare on nutritional inputs for their 2012-13 cotton crop (Anon, 2013). Within nutrition expenditure nitrogen (N) is the most significant input however, nitrogenous fertiliser use has increased to the point where significantly more is being applied in commercial crops than is recommended as part of industry best practice. This additional N is a significant additional cost to growers that can equate to many thousands of dollars spent that does not always result in lint yield increases. The Regional Development Officers (RDO) initiated N trials as a means of gaining an understanding of how N fertiliser management influences Nitrogen Fertiliser Use Efficiency (NFUE) as a simple tool to review crop performance.

What are the potential Benefits Growers are Looking for when planting Cotton into Wheat StubbleΓ Since the introduction of effective knock-down herbicides, farmers all over the world have tried to use zero-tillage practices to achieve better water infiltration, to improve soil structure as well as to reduce the risk of soil erosion through wind or water run-off and pesticide movement off field. Zero-till practices have been well accepted in dryland situations in Australia for quite a while. Dryland growers have been able to increase their yield potential by reducing run off and storing more water in their soils prior to planting as well as daring the growing season. Could similar technology be used in furrow irrigated cotton fields in AustraliaΓ Do the potential benefits outweigh the potential problems like more difficult weed control, stubble handling and plant establishmentΓ Are zero-till systems practical or are they too difficult to handle in a commercial production systemΓ Should we concentrate on the simple and effective systems rather than trying to solve our problems using too sophisticated and complicated systemsΓ