Show simple item record Bange, Michael 2021-10-11T00:03:06Z 2021-10-11T00:03:06Z 2019-06-30
dc.description.abstract A key challenge for the Australian cotton industry is to ensure that its’ reputation for high quality is maintained and year to year variation in yield is minimised. There is also continued pressure to explore changes in agronomic practice to deal with rising costs, reduced terms of trade, need for improved use efficiencies for crop inputs, and in response to technological changes such as new varieties, plant hormones, and precision agriculture innovations. To maintain progress, research is needed to update existing agronomic recommendations as well as identify new practices or tools that increase yield and provide resilience to crop stress in both irrigated and dryland systems. There have been advances made in growth hormone and regulant compounds that could assist in managing stresses (water and heat) in cotton. Past research has demonstrated the utility of some of these hormones, but this was done in lower yielding crops in the USA where their use was often not economically viable. Recent successful research in Australia using an ethylene inhibitor on waterlogged cotton to reduce fruit shedding has highlighted that the use of hormones should be reconsidered for both managing stress and assisting with novel approaches to agronomic management to improve resilience and profit. This project addressed the following research objectives (i) investigate whether the use of novel agronomic approaches utilising various plant hormones could raise yield and build crop resilience to stress, raising profit in both irrigated and dryland systems; (ii) assess an alternative approach to day degree that delivers more precise predictions and assessments of crop development for all cotton regions that will facilitate more accurate growth assessment and management decisions; and (iii) Maintain build crucial independent research capacity in cotton agronomic research through the support of Claire Welsh’s PhD studies in rainfed cotton systems. Growth regulator/hormone research - Over the course of the four years many experiments were conducted to evaluate key research questions. This was a challenging project where experiments were compromised by hail (1 on-farm experiment in 15/16 season, and most experiments at ACRI in 2018/19 season), extreme cold then extreme heat and disease (verticillium) (all ACRI experiments in the 2016/17 season), waterlogging when not required (1 on-farm experiment in 17/18 season), and extreme rainfall events removing lint from the plant (2 on-farm experiments in Emerald in 2016/17). Research addressed the following key questions: • Can yield and quality be improved on fully irrigated crops using consecutive applications of anti-ethylene agents? • Can various combinations of anti-ethylene agents reduce the effects of mild stress in irrigated cotton? • Can anti-ethylene agents improve yield and quality by retaining fruit at cutout using anti-ethylene agents? • Can the use of anti-ethylene agents help with yield reduction associated with a skipped irrigation? • Can a combination of anti-ethylene agents and foliar fertiliser reduce the impacts of a waterlogging event? This was the first research conducted where they will be assessed in combination. The conditions in which this project was undertaken was challenging with the climate extremes experienced. Variability within many experiments was far greater than effects caused by the treatments making it difficult to discern any consistent treatment effects. It was hoped based on the waterlogging experiments conducted in the past that rates and timings would have led to differences. These results potentially highlight that unless there is a severe stress imposed (like a waterlogging event) to prevent significant fruit loss there may be little utility in retaining fruit in less stressful situations. Lack of differences could simply be a result of cotton’s ability to compensate the loss of fruit to allow assimilates to support the growth of existing fruit (resulting in larger fruit; evidenced in this study). This is a known mechanism that cotton uses to overcome stress in milder situations. Overall at the present time, and given the current high cost of these hormones, the multiple application strategies that generated differences would be currently cost prohibitive. Future research should be conducted in more controlled conditions, with greater replication, and with an explicit ability to quantify the stressed conditions. Ability to utilise a technique that can quantify the ethylene hormone response would also aid this research. Therefore, at this time no clear recommendation of the use of these growth regulators to answer the questions addressed in this study can be made. New Day Degree Calculator - Key management recommendations rely on accurate estimates of crop development and boll periods using the day degree approach. The day degree approach is a fundamental tool used to assess crop development against growth and management (eg nutrition sampling, first irrigation) milestones for that particular season’s climate. Currently, the ‘day degree’ approach is not robust to accommodate extremes of climate (heat/cold). There is a need to refine this approach to ensure the accuracy of this critical tool to accommodate temperature extremes and ensure we can use it confidently for management decisions in new cotton regions (eg. Griffith). New approaches will be developed to accommodate temperature extremes improving predictive capabilities and management recommendations that rely on this approach. During the course of this project we have compiled data from multiple seasons where first square, first flower, and sometimes first open boll were recorded. Data was collated from both Australian and USA locations. We compared a number of approaches: 1. The existing industry day degree approach and targets; 2. A modified approach using the existing approach with a maximum temperature threshold and existing thresholds; 3. A published method used in the USA in Arizona; and 4. A method that uses an alternative approach calculating a rate of progress from data measured in the Canberra Phytoton previously published by Bange and Milroy (2001). This study was able to demonstrate that there were improvements in the predictability of time of first square and first flower measured in cotton crops. Two functions were able to better predict these phenological stages compared to the existing function used currently in the Australian industry (Constable and Shaw, 1988). The best performing functions were a variable temperature day degree function that used a base temperature of 15.6 °C and an optimum of 32 °C, and a physiological rate function that reflected similar temperature characteristics as the variable function. The use of these functions should be considered in the development of new cotton crop predictive capabilities as they will be able to account for more temperature extremes (high and low, that maybe more prevalent in a changing climate) and where cotton production moves into new regions. The analyses of functions here also support the use of a base temperature of 15.6 °C (60 °F) used in USA cotton systems. Michael Bange began promotion of the understanding relating to the use of these new functions throughout the industry. An industry you tube video was also developed on the use of day degree functions and included outcomes generated in this study. CSD have also implemented the new function as part of their online suite of agronomy tools en_US
dc.description.sponsorship CRDC en_US
dc.publisher CSIRO Agriculture and Food en_US
dc.relation.ispartofseries CSP1601;
dc.title Agronomy for resilient future cotton systems en_US
dc.type Technical Report en_US

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