Crops entering the final ratoon before plough-out, the last ratoon in a crop cycle, could offer an opportunity to reduce nutrient inputs without affecting productivity. However, several factors should be considered before reducing nutrient rates.
This may be due to favourable growing conditions, good farm management, shorter crop cycles where younger ratoons (eg 3rd ratoon) are ploughed out to maintain a particular block rotation strategy, or other factors.
These crops may show both productivity and economic responses to nutrients applied at SIX EASY STEPS rates.
For blocks entering the final ratoon that are still performing well or have the potential to respond to good growing conditions, the SIX EASY STEPS recommended rate should be maintained.
Many blocks entering their final ratoon are poorer performing than other blocks on the farm.
Poor performance may result from disease, pest damage, harvest damage, weed infestation or weather related impacts.
Understanding the cause of poor crop performance will identify management strategies to improve productivity.
Final ratoon crops in poor condition are less likely to show a response to, or economic return from, nutrients applied at SIX EASY STEPS recommended rates.
Reducing all nutrients by a small amount is unlikely to affect crop performance.
It is recommended that any change in management is tested on-farm. This will build confidence in both the new nutrient rates but also the process of fine tuning a nutrient management program as part of steps 5 & 6 in the SIX EASY STEPS. A guideline for conducting on-farm trials is included in the SIX EASY STEPS toolbox.
Leaf testing also provides a valuable method for checking on the adequacy of nutrient inputs.
In poor performing final ratoon crops, a fertiliser rate reduction of up to 20% could be considered.
Alternatively, a reduction of nitrogen rate alone of up to 20% could be tested if practical.
As final ratoon crops are harvested late in the season (Late season ratoons tool), assess which strategy is most suitable and fine tune the nutrient management program accordingly. This should include on-farm testing to gain confidence in the new approach.
Crops ratooned late in the season should always be fertilised as soon after harvest as practical as rainfall events may prevent access to blocks. Avoid application of nutrients (especially nitrogen) in the wet season where the risk of loss is greatest.
The strategies for crops harvested late in the season and final ratoons should not be combined as the reduction in applied nutrients may be too great (more than 20%), potentially resulting in reduced productivity and profitability.
If circumstances change and the crop is ratooned for an additional season (after nutrient rates have already been reduced once), returning to the SIX EASY STEPS recommended rate would be appropriate.
Papers published from the Australian Society of Sugar Cane Technologists annual conference are also available at www.assct.com.au
Version: April 2020
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