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SEPTEMBER EDITION
FOCUS: EARLY SOWN CROP MANAGEMENT
August Summary
The 2016-2017 cotton season is well underway in Central Queensland. Approximately 4000 hectares of cotton was planted in August in the Central Highlands region. Some dryland cotton was planted in Clermont while Dawson Valley have also been busy planting.

Paul Grundy has kindly written an article, which can be found below, on some of the management tactics that may need to be taken into consideration for August planted cotton crops.
Early August sown cotton at Orana, Cowal Agriculture
(photo taken 1 September 2016)
Cotton Map ready for the season
The Cotton Field Awareness Map is an industry initiative that has been designed to highlight the location of cotton fields. The service is provided free of charge with the purpose of minimising off-target damage from downwind pesticide application.

Growers, farm managers, resellers, consultants, applicators and contractors are encouraged to input their cotton field(s). Users are able to access the Cotton Map to check the location of the field(s) they may be planning to spray to assess the proximity of the nearest cotton field
.

Please let Renee Anderson know if you are experiencing problems with accessing the site.

For any spray drift concerns this season, contact Emerald-based Biosecurity Queensland crop protection officer, John McLachlan-Karr.
2016 Careers in Agriculture Day
The Careers in Agriculture Day is an initative by AgForce Queensland and Emerald Agricultural College that encourages young people to pursue agricultural careers.

Renee Anderson (Cotton Australia), Kelly O'Neill (Ag N Vet) and Sharna Holman (CottonInfo/DAF) as well as DAF researcher, Dr Richard Sequeira and technical officer, Ms Gail Spargo, showcased the cotton industry to high school, agricultural college and tertiary students from over seven high schools in the Central Queensland region. This presentation covered a range of cotton related topics from cotton production, agronomics, research and extension as well as the wide-range of cotton careers and their associated career pathways.
Early sown cotton update 
With the opportunities of Bollgard 3, approximately 4000 hectares of cotton has ben sown during August for 2016/17 season on the Central Highlands. For the most part these crops have had an excellent start with warmer than average conditions throughout August, and soil temperatures that only fell below 14oC for a couple of days in late August.

Establishment has been good with most people establishing 70-80% of the seed that was sown. Disappointingly, there have been low levels of seedling disease recorded in many early sown crops, although not at a level which have caused stand issues. Seedling diseases have not been recorded in the test plantings over the last three years and the key difference, apart from Bollgard 2 vs 3, would appear to be that all earlier plantings used Bion® treated seed. The use of Bion® may need to become a standard practice to consider for when planting future crops during August and early September, particularly as the resilience of newer smaller seeded varieties during establishment is lower than previous cultivars.  


Management considerations for early sown crops between now and first flower
Early sown cotton on the Central Highlands will grow very differently compared to crops planted during the mid-September to October window. Maximising the success of these crops is underpinned by excellent planting practices that ensure effective crop establishment combined with tactical agronomic management particularly between the six node to first flower stage that aims to maximise plant size and ensure row closure by cut out.

The key management objective for the coming weeks is to maximise the ratio of the crop's leaf area to the number of fruiting sites. This is vital for maximising yield potential and early crop maturity. Otherwise said, we want to avoid premature cut out – something that early sown crops are at greater risk.

To achieve rapid vegetative expansion it is helpful to think about life from a plants perspective and look at the factors at play.


Weather
Weather plays a significant role in influencing the vegetative expansion of a crop. Warm temperatures, higher humidity and rainfall will certainly increase a plant's ability for cell expansion which leads to bigger leaves. Alternatively cool conditions with dry air will provide a handbrake for canopy expansion. Fortunately the period between mid-September and late-October on the Central Highlands is a time of significant change with rapidly warming temperatures and characteristic increase in humidity as coastal wind influences become more dominant. The chances are very good that the weather will be on your side in most seasons during this period when trying to encourage rapid canopy expansion.

Fruiting site numbers
Bollgard 3 crops can be expected to have nearly 100% retention of all fruiting sites in the lead up to first flower as weather conditions are very unlikely to cause shedding. Insects are the main agent that can reduce fruiting site numbers and therefore the ratio of sites to leaf area.

Reduced first position retention between squaring and first flower to levels of around 60-90% is likely to be helpful in setting up early sown crops for rapid vegetative expansion. This will ultimately provide the framework for a high yield.  To put this into perspective, there has been an average of 13.5 sites/plant or 170 sites/m row at first flower for the previous early sown experiments. These crops have gone on to produce about 320 sites/m row by cut out. Clearly there is ample opportunity for crops that have lost some squares prior to first flower to compensate during flowering.  Bolls are energy dense and on a gram for gram basis will take about three times more energy than stems and leaf. The cotton plant is very good at not wasting energy so trading in a few positions during the squaring phase will result in those resources being redirected into a bigger canopy during flowering which can in turn underpin a higher yield potential.

So in terms of managing pests such as mirids, allowing some damage may be helpful in enabling the plant to put more energy into building a bigger canopy. Factor in retention data when making insect management decisions and consider delaying control measures if retentions are still very high. This may also have the benefit of reducing the potential for secondary pest flares.    


Pumping up the leaves
There are two levers available for growers to use when aiming to maximise canopy expansion during the squaring and first weeks of flowering - available soil water and nutrition.

Irrigation – ask yourself the question why do we irrigate cotton? The primary purposes are to enable the plant to freely transpire moisture and regulate leaf temperature for efficient photosynthesis and enable the roots to access nutrients in the soil. Having adequate available soil water enables greater leaf cell expansion so it is important to ensure that soil moisture is not limiting leading up to flowering.

Similarly it is worth considering crop nutrition both from a fertiliser and plant access perspective. A management objective should be to have the crops' fertiliser needs largely in place by squaring. This should take into account whether or not you plan to apply supplemental N during early flowering. Thinking about the plant, as managers we should aim to ensure that the plant can maintain a highly active root growth and function within the parts of the profile where the soil is most fertile. Taking into account that our replacement of the relatively immobile P and K elements, is via fertiliser applied in the top 30cm of the profile, the most fertile areas are going to be within or just under the hill. Using large irrigation deficits early in the crop in a bid to 'drive' the roots deeper is likely to be counter-productive in a fully irrigated system. This is because a good proportion of the roots that would be foraging the more fertile upper layers will be less active for longer.

Running smaller deficits earlier in the life of the crop may run counter to people’s previous cotton growing experience. There has been a tendency to force the crop to put down deeper roots prior to flowering by stretching irrigations, but for early sown crops it is important to ensure that crops have good access to moisture and nutrition so that the plant can direct its resources towards canopy growth. Water use calculations from the early sowing trials over the last two seasons have shown that despite using smaller irrigation deficits and more frequent irrigation frequency, overall water use was still less than later sown crops as peak leaf area coincides with cooler temperatures during late November and December, as opposed to January. With efficient application practices around duration (to avoid water logging), flow rates and tail water recycling, managing more regular irrigation intervals does not have to equate with greater overall water usage. This approach is likely to assist more rapid greater canopy expansion. Keeping the roots active more regularly in the upper parts of the profile is also likely to benefit early season crop growth and canopy development.  Gradual increases to irrigation deficits can be slowly enacted as the crop moves from flowering to cut out. For the early planted trials over the previous two seasons, the initial deficits prior to irrigation were in the 30-40mm range with deficits increasing to 40-50mm later in the season depending on environmental conditions.


Concluding remarks
Keep it simple and think like a plant. Anything that you can do as a manager to help the plant to increase the proportion of leaf area to the number of fruiting sites during the squaring phase is likely result in a larger canopy and yield potential by the cut out stage.

Paul Grundy, Queensland Department of Agriculture and Fisheries
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The information contained herein is subject to change without notice. The Queensland Government and CottonInfo shall not be liable for technical or other errors or emissions contained herein. The reader/user accepts all risks and responsibilities for losses, damages, costs and other consequences resulting directly or indirectly from using this information.

For any feedback, questions or suggestions for future topics please contact
Sharna Holman
CottonInfo and Queensland Department of Agriculture and Fisheries
M: 0477 394 116
E: sharna.holman@daf.qld.gov.au


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