The aims of the project were to determine the effect of selected management practices on

carbon sequestration, soil quality and hydrology, crop agronomy and profitability in irrigated

and dryland Vertosols using a combination of field and laboratory experiments, and desktop

studies. Management practices were tillage systems, rotation crops, soil amendments,

irrigation and stubble management. Measurements included environmental variables such as

soil quality, carbon storage and sequestration, greenhouse gas emissions, deep drainage and

soil water storage, and agronomic variables such as above- and below-ground crop growth

and cotton lint yield. Economic returns in irrigated sites at ACRI were evaluated by

comparing seasonal and cumulative gross margins. Partial life cycle analyses of greenhouse

gas emissions were made using a desktop approach. The “Mulch Manager”, a machinery

attachment which was able to kill vetch while reducing herbicide application rates and

trafficking was completed and assessed.

In general, SOC stocks in the 0-60 cm depth ranged between 50 and 70 t/ha. Legumes,

although contributing large amounts of carbon to the soil were unable to retain it because their low C/N ratio facilitated rapid microbial decomposition. Carbon inputs of C4 crops such as sorghum and corn were much larger than those of C3 crops such as wheat. A major proportion of that carbon came from their root systems. Increasing water availability and reducing tillage improved root growth. SOC sequestration rates were generally negative or neutral, except where a stressed soil (disease, sodicity, salinity) was in the process of recovering.

Estimates of carbon inputs, based on above-ground and root dry matter, together with measured sequestration rates indicated that large losses of carbon were occurring, probably due to a combination of accelerated erosion, runoff and microbial decomposition. SOC storage was positively related to dry matter inputs, average maximum temperature, soil aeration and water availability but was negatively associated with N fertiliser inputs. Except for temperature, the other variables can be manipulated by cotton growers. Average maximum temperature and soil organic carbon in the 0-60 cm depth had a curvilinear relationship. The temperature optima were higher in the Namoi valley (27-28 oC) than in the Macquarie (25.5 oC). Farming practises that could reduce emissions include eliminating inversion tillage, minimising use of groundwater, sowing winter crops in rotation with cotton, reducing/optimising mineral N fertiliser rates, substituting a legume an thus, fixed N for mineral N fertiliser. Long-term cropping-related K depletion may be minimised by regular application of cattle manure. Gypsum application did not improve subsoil structure under dryland conditions, probably because of the erratic rainfall pattern.

Water losses through drainage can be reduced and soil water storage increased (i.e. water

conservation improved) by including a wheat crop in the rotation with in situ stubble retention under less frequent irrigation. Management systems that conserve all rainfall received in situ, thereby reducing irrigation water requirements can contribute greatly to the sustainability of irrigated cropping. Deep drainage in cropped plots under normal or low rainfall conditions was many times higher than that in fallow plots, and reflects the higher water inputs in the former. When rainfall was frequent and no irrigation was required, drainage was higher under fallow, with fallow length being positively correlated to drainage. A model was developed that used rainfall and potential evaporation to estimate soil evaporation from beds where stubble was either incorporated or retained in situ. A model that used EM38 measurements, soil water storage and sodicity (ESP) was able to accurately estimate chloride in non-saline soils. These values could then be used to estimate drainage using chloride mass balance models.

Cotton yields and gross margin/ML were generally higher when wheat was included in the

rotation with highest values occurring on permanent beds. Amendments such as gypsum or

manure did not improve crop yields under dryland conditions, even though soil quality was

improved. Including vetch in the rotation did not result in sufficient improvements in cotton

yield to compensate for the increase in production costs. In years of plentiful water (or when

crop area is the limiting factor) reducing water application rates on a continuous cotton crop

was a false economy.

Cotton lint yields, in general, were positively related to water and N inputs, soil aeration in

some sites and average annual daily maximum temperature in cooler or poorly-drained sites

but were lowered by higher average annual daily minimum temperature. In a sodic soil, a high frequency of the tillage practices intended to aerate the soil may have caused yield decreases, presumably due to exposure of more sodic soils. Depth and frequency of tillage, average annual maximum and minimum temperature, N and SOC directly affected WUE of cotton. Except for SOC, which had no effect, all of the above variables directly affected NUE of cotton, particularly N fertiliser rate, which was negatively related, and legumes, which were positively related. The relative importance of individual variable differed among sites for yield, WUE and NUE.

The “Mulch manager” reduced use of herbicides, decreased labour, lowered risk to operators

and had a lower carbon footprint. In comparison to spraying with an 8-row boom sprayer,

depth of compaction was more when this 4-row implement was used, although the former

resulted in more intense and shallower compaction.

Between 2008 and 2011, two postgraduate students, two honours student and a visiting fellow from Pakistan were hosted by the project. Project outputs were: 7 journal articles, 11

conference papers and 5 cotton industry and extension. A total of 16 public presentations were given by project and associated staff.

Key outcomes included:

• Identifying soil and crop management practices, and climatic variables that had direct

impacts on soil carbon stocks, yield, water and nitrogen use efficiency in irrigated cotton

soils.

• Quantifying rainfall harvested, and associated drainage and evaporation, and thus, water

saved by retaining rotation crop stubble as in situ mulch.

• Identifying practices that could reduce carbon footprint of cotton farming systems with

life cycle analysis.

• A machinery attachment for managing prostrate cover crops bed-furrow systems.

• Simplified field methods to estimate soil evaporation and deep drainage.

• A whole-farm model of profitability for cotton farming systems that can be used as an

analytical research tool

This study was carried out in afield trial on black clay soils in the Macintyre cotton growing region during a 2005/2006 cotton season and future improvements on this experiment may see significant results that will give us a better understanding of the K and B effects on cotton development, which may lead to improvements in agronomic practices.

The study will was the first stage of a process aimed at assisting the industry and its communities to manage change effectively. The industry will benefit from a better understanding of the factors affecting the economic and social condition of cotton communities, the change processes in those communities, and the means by which these factors and changes might be managed. In the discussion of possible socio-economic topics at the 'Industry and Community' meeting at UNE in April 2005, a strong consensus emerged that a necessary component of research in this area would be to select indicators that could be used to track the economic and social condition of cotton communities over the life of the CRC and beyond. Such indicators could have a variety of uses, including:helping the industry to monitor its influence on the rest of the community; helping the community to monitor its influence on the industry; helping stakeholders in both community and industry to understand the changes they were undergoing; and helping both industry and community manage these changes and interactions. The Main Project Aims were to:scope the selection of socio-economic indicators for cotton catchment communities engage stakeholders in those communities in the identification of issues relevant to the sustainability of their livelihoods engage stakeholders in the definition of indicators relevant to their communities. The report of the study will serve as a basis for addressing some of the specific questions posed in the Cotton Catchment Communities Prospectus.

Water remains a key issue for the cotton industry, with improving water use efficiency a priority. Relatively water research has focussed on the plant and its interaction with the soil and climate. Currently deficit irrigation and many different row configurations are used in the cotton industry without accurate knowledge of how these irrigation regimes affect root development. Water deficit and irrigation can influence cotton plants root systems: dryland cotton has deeper roots than fully irrigated crops and the timing of first irrigation can be used to encourage good root development. These affects are important in overall plant responses to moisture stress.

A thesis submitted in the form of two papers for fulfilment of the requirements for the degree of Bachelor (Land and Water Science) Faculty of Agriculture, Food and Natural Resources The University of Sydney

The primary purpose of DAQ 122C was to investigate alternative pest management options under central Queensland conditions with a view to supporting and expanding the role of area wide management. The project accomplished of a broad suite of research spanning the use of assassin bugs as applied biological control agents through to investigating the potential of using attract and kill technology (Magnet®) for the management of Helicoverpa and Bt resistance.

The threat of ascochyta leaf blight disease gaining a foot-hold within the CQ chickpea industry provided an impetus to re-investigate alternative legume options for spring trap cropping. Field peas (cvs Alma or Glenroy) were found to be the most effective legume for Helicoverpa trap cropping and were unique in that the majority of eggs laid on it perished due to dislodgement from the waxy foliage making it a partially self-maintaining trap crop. The adoption of field peas for spring trap cropping circumvents any problems associated with chickpea leaf blight disease.

The use of refuges to augment natural enemies in cotton was investigated, with niger identified as being attractive to the broadest range of natural enemies. However, the use of refuges was found to be a inconsistent method for augmenting natural enemies commonly associated with cotton systems. The patterns of natural enemy abundance observed in the refuge treatments were probably more closely associated with variations within the surrounding environment than any in-field modifications to vegetative biodiversity via the provision of refuges. These results suggest that the key to reliably predicting and augmenting endemic populations of natural enemies within cotton farming systems may potentially exist in developing a more refined understanding of the interactions that occur between beneficial species and the broader natural environment.

The assassin bug, Pristhesancus plagipennis was demonstrated to be an effective biological control agent for Helicoverpa and mirids in conventional cotton. Assassin bugs were found to be innately tolerant of Steward®, Admiral®, Tracer®, Regent® and Affirm®, as well as NPV and Bt biopesticides. The compatibility of these products with assassin bugs in the field is highly desirable and our experiments demonstrated that the strategic integration of these insecticides with releases of assassin bugs provided effective pest management with 50% less insecticide whilst maximising crop yield. Should assassin bugs become commercially available in the future, significant potential exists utilise them within a low spray IPM program for conventional cotton.

Population dynamic studies demonstrated that Silver Leaf Whitefly, Bemisia tabaci Biotype (B) has become a regular pest of cotton within the Dawson Valley, infesting crops each year during late November and December and peaking in abundance during February. Sampling has also determined that native Eretmocerous parasitoids have become well established with their increased abundance correlating with a reduction in regional whitefly populations on cotton. Mean parasitism rates recorded in cotton have risen from 15% in 2003 to 87% in 2005 whilst applications of Insect Growth Regulators (IGRs) for whitefly control have decreased from 40% to <5% of fields over the same period. The reduction in IGR use constitutes savings of $100 per hectare not treated. Our data suggest that it is imperative to ensure the compatibility of pest management practices with whitefly parasitoid conservation and that this consideration will continue to influence future pest management research.

DAQ122C identified the potential for using Magnet® as a regional moth busting tool for targeting last generation Helicoverpa emerging from Bollgard® fields. Such an approach could supersede the requirement for summer trap cropping as part of the CQ Bt resistance management strategy and will be the focus for future research. Refinement of the current Bt resistance management strategy is of critical importance to ensuring the prolonged viability of pesticide reducing transgenic technologies.

Best pest management practices and novel research outcomes were promoted to CQ cotton growers throughout DAQ122C via several interactive field days each season and the provision of significant technical support and input for three IPM short courses conducted in the Dawson Valley and Central Highlands regions of CQ.

Experiments to establish the response of cotton plant to soil water stress under different soil types, climatic conditions and fruiting loads have shown that (i) the response of cotton to water stress is different on different soils (eg heavy clay vs. sandy-loam) (ii) these differences can be accounted for when soil moisture content is normalised for water holding capacity, expressed as the fraction of transpirable soil water (FTSW) (iii) that climate, especially evaporative demand, can cause plant stress even when the crop has adequate soil moisture and (iv) there is no difference in soil water extraction and therefore root development by crops with different levels of fruit retention.Field experiments were run over three cotton seasons at three sites with widely different soil types around Narrabri NSW. The response of the cotton plant to moisture stress, imposed by skipping irrigations around flowering, was measured as leaf water potential using a pressure chamber. Cotton plants were found to behave in the same way to moisture stress on all soil types when the soil water holding capacity of the soil was taken in to account and expressed as a percentage or fraction of transpirable soil water (FTSW). Over the three seasons prevailing climatic conditions have a large effect on the ability of the plant to cope with a given level of soil moisture deficit. Even under low levels of soil moisture deficit, on high evaporative demand days plants often experienced stress which had an impact on yield. There are some climatic conditions under which the cotton plant is unable to take up enough moisture even from a soil profile with readily available water that the plant will become stressed no matter if more water is applied. Identifying these conditions and their management implications are the subject of ongoing research.The results of this research will provide a basis for refined irrigation management through understanding the effect of climate and soil type to reduce water stress and providing decision points for future management. This information will also be included in decision support systems through inclusion in future versions of HydroLOGIC.A separate experiment conducted over two seasons also in Narrabri showed no difference in soil moisture extraction and therefore extent of root development between crops that have high and low levels of fruit retention before cutout. High retention crops (such as BG II®) should be irrigated in a similar manner to lower retention cotton. The high level of early reproductive development does not appear to affect the below ground vegetative development of the crop. A preliminary experiment was also conducted to investigate partial rootzone drying in cotton. This showed no benefit from partial rootzone drying in terms of cotton plant stomatal control, biomass production or yield.This project has significantly improved our understanding of basic responses of cotton to soil moisture stress and how this is influenced by climate and soil type. This knowledge is vital in developing improved irrigation strategies for cotton and achieving maximum yield from applied water.

The aim of this study was to use EM imaging and .a collected by a DUALEM-421 to infer the spatial distribution of soil properties and soil particle size fractions related to .a across a prior stream channel in an irrigated cotton field in the lower Gwydir valley. EM imaging is defined by Christensen (1997) as an approximate inverse mapping of data into a model.

This project is about the development and interpretation of a range of socioeconomic indicators for a sample of case study communities where the cotton industry is a significant industry. This is one of the reports from this project and relates to the economic indicators and their interpretation.

An essential component of the plant body is the root system. It provides anchorage and support for the plant to explore its substrate, to absorb water and nutrients and to transport them above ground to the shoot system. Root systems are highly adaptive and responsive to environment flux (Stokes et al, 1996, Annals of Botany 78: 415-421).The root systems in cotton may vary in different cultivars, for example, cultivars infected with different soil-borne pathogens and cultivars with varying levels of disease resistance may show different root characteristics. The soil-borne black root rot and fusarium (Fov) wilt pathogens have been used in this project to determine whether different disease resistant lines show variations in their root architecture. The root architectures between different genotypes grown under normal conditions are also assessed in this project. More robust roots in cotton cultivars are of great agronomic significance in its potential to protect against cotton diseases without the need for chemicals. Cultivars showing robust root characteristics may be incorporated into new lines.It was found that cotton root architecture varies with genotype. Additionally, cotton cultivars respond to exposure to the pathogen Thielaviopsis basicola with some cultivars showing an increase in root branching and others showing a decrease. Furthermore, degree of root branching was seen to vary with relative resistance to the fusarium wilt pathogen