A CSIRO investigation into the viability of growing cotton in the Burdekin region has recorded significant yield results for ENTEC fertilisers in its trial program in 2013.
ENTEC was included to see whether it could help provide crops with adequate nitrogen during the wet season.
CSIRO Plant Industry Principal Research Scientist, Stephen Yeates, said the trials had been running for four seasons, with ENTEC introduced over the last two seasons.
He said a core group of cane growers in the Burdekin had been interested in cotton for a number of years due to low cane prices and the need for a profitable break crop. Cotton’s evaluation as a rotation crop option is continuing.
At this stage, any cotton produced in the Burdekin is sent to a gin in Emerald, at least 600 km away.
“We can’t just take a southern approach to growing cotton and apply it to the Burdekin – it doesn’t work,” Dr Yeates said.
“In the Burdekin, the early growth stages of the crop coincide with the wettest time of the year, with planting from late December to early January,” he said.
“The wet weather leads to nitrogen losses from the soil, either by leaching or denitrification and poor nitrogen uptake, limiting yield potential.
“The crop isn’t getting a chance to access the nitrogen applied at planting because it is being lost even before it has established its root system.”
In response to these challenges, Dr Yeates developed a test fertiliser program which reduced nitrogen at planting and added more nitrogen one to two months later.
“Splitting nitrogen with EASY N® appears to improve yields dramatically, particularly on the sandy soils,” he said.
“On the clay soils, it depends on the season, because when it continues to be wet, we can’t get on to the paddock to top up the crop’s nitrogen supplies.”
This was when Dr Yeates and his research colleagues started to consider using ENTEC.
“We thought we would try applying a nitrogen fertiliser that wouldn’t be converted to nitrate so rapidly, after discussing the potential for ENTEC with Rob Dwyer, Incitec Pivot Fertilisers’ Technical Agronomist who is based in the Burdekin.”
Dr Yeates said any treatment that slowed the release of nitrate into the soil had potential to work in crops grown through the wet season, including cotton, cane and corn.
“Loss of nitrogen is a challenge during the peak of the wet season for all crops.
“When soil conditions are hot and wet, urea can convert very rapidly to nitrate and we know we get nitrate washing out into the furrows.
“When the soil gets wet, it can also be anaerobic which can mean nitrate is subject to denitrification losses as well.”
Stephen explained that holding a significant proportion of the early applied nitrogen out of the nitrate form until the roots were established, say 30 days, seemed ideal, because then it would be available when the crop was ready to use it.
The 2012 trial results for the ENTEC treatment were encouraging.
Dr Yeates said they recorded greater efficiency of nitrogen uptake where urea with ENTEC was used than where urea was used in 2012. This was measured with tissue testing.
However, the good early signs did not lead to improved yields.
“It was cloudy and wet in March and April when the bolls are filling and we believe yields were capped by a lack of solar radiation.”
In the 2013 season, visual differences could be seen between the urea with ENTEC treatments and urea treatments at a field walk in May, despite below average rainfall.
Fertiliser uptake was also higher where ENTEC was used.
Nitrogen uptake from fertiliser increased from 29.6 per cent where 300 kg/ha of urea was applied to 38.4pc where 300 kg/ha of urea with ENTEC was applied.
This improvement was reflected in yields, with 300 kg/ha of urea with ENTEC providing the highest yield result of the trial at 8.53 bales/ha of lint yield. This was significantly higher than in the 300 kg/ha of urea treatment, which yielded 7.94 bales/ha.
Dr Yeates is also testing polymer coated urea in the trials while continuing the split nitrogen treatments.
While 2013 was only the first year polymer coated urea was trialled, it performed well, providing excellent nitrogen uptake (57.3pc) and yield (7.45 bales/ha) results at a rate of only 150 kg/ha.
