Don't let leaching be a drain on yields
Leaching is the movement of nitrate nitrogen with water beyond the plant root zone. This dreaded drain can happen any time the amount of rainfall or irrigation on the block is more than the soil can hold internally.
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Soil types vary in their capacity to hold and store moisture. Sandy, lighter soil types are renowned for being ‘leaky’, while clay or loam based soils have a higher water holding capacity.
Of course, the largest losses occur when there are large amounts of nitrate nitrogen in the soil, such as in the weeks after the application of a traditional urea based fertiliser blend. Large storms or days of rain at this time can cause significant losses – enough to set back crop growth and even result in yield reductions.
In fact, the timing and distribution of rainfall is thought to be one of the most significant influences on cane yields, according to research by Barry Salter from Sugar Research Australia.1
Managing leaching
For a long time, leaching losses have been largely unmanageable for cane growers. The strategies available included splitting nitrogen applications and using fallow legumes to store nitrogen.
Mostly, growers just hoped to be able to get crops up to a height of around 1.2 to 1.5 metres before a big leaching event, so that most of the nitrogen applied was already taken up by the crop.
And while we still can’t turn off the rain when crops have had enough, we now have a tool to manage leaching in cane – ENTEC®.
ENTEC stabilises fertiliser nitrogen in the ammonium form, so that large pools of nitrate nitrogen are not sitting in the topsoil at risk of leaching. Because ammonium is positively charged, it sticks to the soil rather than moving with water flows through the soil.
Ammonium is also sugar cane’s preferred source of nitrogen2. Even if both ammonium and nitrate are available in the soil, the crop will take up the ammonium first.
This means growers using ENTEC are giving their crops a strong start with a good supply of nitrogen, while protecting against leaching losses.
Taking action
Growers can assess the risk of leaching on individual blocks with soil tests from the Nutrient Advantage® laboratory. Soils most at risk of leaching losses will be those with a cation exchange capacity of less than four cmol (+)/kg. On these blocks, use ENTEC to reduce the potential for leaching
losses.
For more information
For more information about using ENTEC to manage leaching (and additionally denitrification) see your local ENTEC accredited fertiliser Dealer. Don’t let leaching be a drain on your cane yields this coming season!
Also, feel free to contact me on 0428 111 471 or rob.dwyer@incitecpivot.com.au.
Rob Dwyer
Tropical Systems Agronomist
Incitec Pivot Fertilisers
published in the Aust Soc Sugar Cane Technol Vol. 34.
2 “Nitrate fertiliser wasted on sugarcane” (2011) UQ News, The University of Queensland Australia
(www.uq.edu.au/news/article/2011/05/nitrate-fertiliser-wasted-sugarcane)