Honours - Root growth, turnover and soil microbial biomass in Bt and non-Bt cotton (Gossypium hirsutum L.)

Cotton production in Central Queensland will continue to impose a unique set of challenges due to climate and it’s remoteness from other production areas. These challenges have been met successfully at an industry level in the duration of this project through strong collaboration between growers and local extension network.

Through the duration of the 5 year project, the cotton industry in Central Queensland has met and addressed some of it’s greatest ever challenges. The highlights of this include the successful development and utilisation of a management strategy for silverleaf whitefly, and the successful development and deployment of a strategy to prevent weed and disease movement into the region, and the establishment and nurturing of successful Area Wide Management Groups.

The project has been instrumental in developing a management program for one of the biggest insect threats, silverleaf whitefly. Without proper management, the destruction of fibre quality could permanently affect the marketability of Australia’s multi-million dollar cotton crop. The management strategy has been developed and adopted through strong collaboration between national and international research and development agencies and farmers and consultants. The template for management of this pest has been able to be transferred to other cotton growing areas in Australia.

The Central Highlands is one of the only cotton producing regions in Australia that has no confirmed cases of Fusarium wilt. The local industry took the proactive step of trying to maintain this status by developing a strategy to prevent the introduction of weeds and diseases into the region. This three-part plan involved 1) the compilation of a protocols document to be used by growers in implementing ‘on farm’ strategies, 2) establishing a facility for independent inspection of machinery entering the area, and 3) a wider community/ industry education program promoting the strategy including the installation of large road signs at the entrances to the district promoting the ‘Come Clean- Go Clean’ message. This program has had great success with excellent adoption and a continued ‘fusarium free’ status.

Central Queensland has been one of the pioneering regions for area wide management following the broad adoption of trap cropping in the late 1990s. Since that time, the momentum of area wide management has continued to grow to an extent where the groups operating in this region are amongst the most dynamic and successful in the industry. The involvement of the extension officer in this project has been paramount to maintaining the momentum of these groups. Outcomes of these groups have included the successful deployment of the management strategy for silverleaf whitefly, the ongoing high adoption of the IRMS and reduced incidences of odour complaints into town.

Whilst the successes of the Central Queensland cotton industry over the past 5 years have been principally been due to the fact that it has industry- wide involvement in all issues, the role of the extension officer in this process has been paramount.

Final Report Cotton yield and soil carbon under continuous cotton, cotton-corn and cotton-wheat

Final Report improving cotton yields on sodic soils - a new role for plant growth regulators Sodic soils present a major management constraint for large parts of Australia's cotton producing districts. A combination of structural, chemical and water constraints in these soils leads to reduced plant growth and yields (Yadav et al. 2011). One primary area of concern is the effect of sodicity in reducing the drought tolerance of cotton plants, particularly seedlings. Because much of the soil moisture stored in the top 10cm of soil is lost to evaporation, it is vital that seedlings can quickly access moisture at greater depths. Sodic soils compound this problem in multiple ways. The chemical environment reduces theosmotic potential, and thus the ability of the young plants to draw sufficient water. Also, the dispersive nature of these soils creates crusting and blocks macropores, reducing infiltration and overall water supply under rain-fed conditions (Ghosh et al. 2010). Along with these factors, sodic soils, particularly Vertosols, can demonstrate high soil strength which makes it difficult for seedling roots to penetrate the soil (Odeh and Onus 2008). Cotton plants arewell adapted to water stress and the chemical environment of sodic soils (Dodd et al. 2010). Most growth constraints, therefore, are likely to be attributable to structural limitations in physically preventing root access to water.Mepiquat chloride is a synthetic plant growth regulator widely used in cotton production to maintain a regular crop and prevent excessive vegetative growth under high temperature conditions (Yeates, Constable and McCumstie 2005). It reportedly interacts with natural plant hormones, increasing the levels of auxin and cytokinin hormones in the middle region of the primary root (Duan et al. 2007), and suppressing gibberellin biosynthesis (Yeates, Constable and McCumstie 2005). The suppression of gibberellin production is believed to slow internode lengthening by limiting cell enlargement (Reddy, Reddy and Hodges 1996), which is the agronomic effect intended. Duan et al. (2007) found that mepiquat chloride also increased lateral root primordia development and lateral root growth, apparently in connection with the increased levels of auxins and cytokinins. Other reports have also found increases in root growth from treatment with mepiquat chloride (Xu and Taylor 1992; Iqbal et al. 2005), which can have beneficial effects in terms of drought tolerance, particularly forseedlings (Xu and Taylor 1992).

Heliothine caterpillars and silverleaf whitefly (SLW) are the major pests of field crops in central Queensland (CQ). Helicoverpa has been the primary focus of cotton insect pest managmenet since the inception of the CQ industry in the ‘70s. SLW is a recent introduction to the mixed cropping systems of CQ. Both pests are serious threats to cotton.

Although the advent of Bollgard II Bt cotton varieties has largely relegated Helicoverpa to minor pest status, the continuing threat to cotton from this pest stems from its ability to develop resistance to the technology. SLW is a major threat to the cotton and grains industries. The excretion of sugary ‘honey dew’ by nymphal and adult SLW feeding on the underside of cotton leaves can make the lint sticky and unmarketable. Large populations of SLW can totally destroy susceptible legumes (eg, soybean) and sunflower plants.

This project demonstrates one approach to coordinating and analysing hydrogeological data to help with the evaluation of catchment water management issues. The methodologies presented in this report are not intended to replace existing approaches to coordinating hydro geological data being used by NSW state government water management departments. Rather the applications presentedcomplement.7

Final Report Molecular analysis of pathogen-cotton interactions

The aims of the project were: (1) Use composted cotton gin trash and pelletised cotton gin trash to

monitor soil response and soil nutrition benefits; (2) Establish experimental woodlots of

tolerant eucalypts with pelletised cotton trash to manage groundwater recharge,

and prevent salinisation, and improve soil carbon stores; and (3) Monitor the impact of the

woodlot and cotton waste material on soil quality, salinity and groundwater levels.

Baseline soil sampling and field mapping of the experimental site were completed by July and

experimental plots laid out by August. The soil analyses showed that the site was very saline and

sodic. Because of drought and extreme salinity, planting of trees and application of composted gin

trash was deferred until autumn 2003. Following this, because of possible contamination with

pesticides through composted gin trash application, the Environmental Protection Agency of NSW

expressed concerns on its use as a soil ameliorant. Pesticide residue analyses showed that very

small amounts of DDE, a degradation product of DDT was present. This is likely to have come

from soil, not cotton gin trash, as it was absent in the latter. A subsequent meeting between CRDC

(represented by Guy Roth) and the EPA failed to resolve the issue. Consequently the project was

aborted as a result of the impasse with the EPA and reduced funding from CRDC. However

Saltgrow is looking into continuing the project independently using an alternative source of

composted recycled green-waste.

The potential use of pheromone traps as a monitoring tool for the cotton pest green mirid (Creontiades dilutus) was studied at three sites. The trials compared pheromone catch numbers to the number of adult and nymph green mirids, the sex ratio, and the percentage of mated females in the field population that were sampled using visual, suction, beat sheets and sweep nets.

Summer scholarship with Wendy Timms This project examined the quality of surface water and groundwater in the Quirindi-Gunnedah area of the Upper Namoi catchment in Australia's Murray-Darling Basin. While several studies have assessed salinity, this is the first project to examine a wide range of water quality parameters including nutrients and agricultural chemicals since the Liverpool Plains Water Quality project 1997/98. In addition, for the first time, many trace organic constituents related to human activity were assessed. Sampling was conducted in January 2012.Surface water salinity was relatively low as expected (<1500 cm-1, except Native Dog Gully), within Namoi CMA salinity targets. In contrast to most sample sites in the Mooki catchment, Native Dog Gully demonstrated salinity, sodium and chloride measurements that far exceeded all crop and drinking water salinity guidelines. However, this is partially mitigated by the negligible discharge, although this area remains a salinity hotspot. The surface water salt load calculated for 2011, 128600 tonnes/year, was slightly lower than that measured in 1998, 146000 tonnes/year. This negates predictions for an increase to 305,000 in 2020 (Beale et al. 1998).However, groundwater salinity was found at levels above or approaching the upper limit of the Namoi CMA guideline for irrigation water, highlighting a gradual increase in groundwater salinity at some sites outlined by Timms et al. 2009.Trace organics of anthropogenic origin were widely detected in both surface and groundwater, including pharmaceuticals, cosmetics and caffeine. Caffeine was the most widely detected organic and while most organics were not of concerning concentrations, their widespread presence raises questions as to the persistence of some human excretions in environmental waters. The only guideline exceeded was for atrazine and simazine with respect to the precautionary aquatic ecosystem protection guideline (99% of ecosystem inhabitants). However results did comply with crop and drinking guidelines.The calculated hydraulic gradient from surface to groundwater values, suggests that rivers contribute a portion of the recharge to groundwater, although the magnitude of this remains undetermined. The stable isotope ratio of most groundwater samples was depleted relative to modern rainfall, suggesting primary recharge of those aquifers was from a wetter climate, or recharged during high intensity rainfall events, though the age of the water was not determined. Liquid Chromatography - Organic Carbon Detection (LC-OCD) a new technique for analysing dissolved organic carbon (DOC) in water, showed a clear differentiation between surface and groundwater. This is the first groundwater LC-OCD analysis in this area and presents scope for further study.