The results of fertiliser trials on sugarcane crops in Far North Queensland could provide the sugar industry with major economic and environmental benefits, according to Primary Industries and Fisheries.
The trials compared cane grown from setts (newly planted cane) using three fertiliser options:
• mill mud, ash and legumes only;
• mill mud, ash and legumes with artificial fertiliser; and
• mill mud, ash and legumes with artificial fertiliser and top dressing.
According to QPI&F, the results showed crops grown without any artificial fertiliser produced 114 tonnes of sugarcane per hectare, 17.6 tonnes of sugar which is a commercial cane sugar percentage (ccs) of 15.48.
Crops grown wit h artificial fertiliser added at planting produced 121 tonnes of sugarcane per hectare and 17.8 tonnes of sugar with a ccs of 14.96.
When fertiliser and top dressing were added to the mix, 121 tonnes of sugarcane was produced per hectare, 18.1 tonnes of sugar with a ccs of 15.02.
When you take into account fertiliser costs, the trial crops grown without artificial fertiliser were more profitable.
Under trial conditions it cost $600 per hectare to fully fertilise the crops and $700 per hectare to install the mill mud and ash.
"Given many producers already use mill mud and ash, the trial showed farmers can save $600 per hectare on fertiliser costs," Primary Industries Minister Tim Mulherin said.
"Producers should be able to reduce their reliance on costly artificial fertilisers through the planting phase.
"These savings not only translate into a more profitable bottom line for producers, but also reduce the risk of excess nutrient running off in to waterways.
"I am certain producers want to reduce fertiliser costs, provided it did not compromise sugar production or sugar quality."
Mr Mulherin said the results back up BSES Limited's advice that cane growers would save money and reduce the use of fertiliser if they stopped adding it to mill mud.
"Mill mud, ash and legumes provide a wider range of nutrients that break down more slowly into the soil," he said.
"The slow release of nutrients means the planted cane is able to use it as it is released and there will be less surplus in the soil."
Mill mud is simply mud and dirt on the cane that is washed off at the mill, whereas the ash comes from the bagasse, which is used to power all of the mills.
These products are readily available at the mills, with mill mud is rich in phosphorus and ash is high in potassium.
QPIF senior agronomist Derek Sparkes said the best time to apply the mill mud and ash was when preparing t he ground for planting legumes.
"Start growing legumes, such as soybean, in the fallow in November/December, then in May, till the soil ready for planting cane," Mr Sparkes said.
"A fully grown crop of legumes contains 100-300kg of nitrogen per hectare, depending on the legume species.
"Legumes provide nitrogen to the soil and also provide an important pest and disease break," he said.
"Mill mud, ash and legumes contain organic matter and improve soil structure and drainage, providing food for beneficial soil microbes.
"Producers living near mills would benefit from greater access to mill mud and ash, but this technique can only be used for planted cane, not ratoons."
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