Cropping

Thinking of chickpeas? Think potassium

Grain Central, April 13, 2017

AS GROWERS continue to replace wheat in their rotations with chickpeas to capitalise on higher market prices, there’s a growing need to update fertiliser programs – or face nutrient run down.

Bede O’Mara

Incitec Pivot Fertilisers’ sub-tropical farming systems agronomist, Bede O’Mara, said one of the major differences between growing wheat and chickpeas was that chickpeas removed significantly more potassium.

“This increased potassium removal will add up for growers who are now regularly including chickpeas in the rotation, particularly if they are growing the crop year on year with other higher potassium removal crops such as cotton and high yielding summer grains like sorghum or corn,” he said.

Last season, Mr O’Mara arranged grain testing to provide up to date guidance on nutrient removal from chickpea crops.

The test results showed that one tonne of chickpea grain removed 10.7 kilograms of potassium – nearly three times more than one tonne of wheat (3.7kg).

The chickpea crop also removed more nitrogen, phosphorus and zinc per tonne of grain than wheat.

Chickpeas were shown to remove 37.4kg/t of nitrogen, 4.1kg/t of phosphorus and 35g/t of zinc in the tests, conducted by the Nutrient Advantage laboratory.

“When you multiply these figures by the high yields that many growers achieved last season, it could well have been a high removal event for those paddocks,” Mr O’Mara said.

“If chickpeas become more of a pillar crop in the rotation, they will come at a larger nutrient removal cost.”

Potassium deficiency

Mr O’Mara said there had been some confirmed and suspected cases of potassium deficiency in chickpeas over the last few seasons on soil types known for being on the lower side of adequate. These includes many box soils and other variable soil types.

Acting on these insights, Incitec Pivot Fertilisers has created a new fertiliser blend for chickpea crops, called ChicKP SZ.

The new fertiliser contains six per cent nitrogen, 11.4pc phosphorus, 19.1pc potassium, 10.7pc sulphur and 0.7pc zinc. Most of the sulphur in ChicKP SZ is in the sulphate sulphur form for immediate availability to the crop.

Mr O’Mara encouraged chickpea growers to consider rates of around 100kg/ha of ChicKP SZ at planting on 50cm or narrower rows, rather than using their standard cereal starter fertiliser which contains no potassium.

On wider rows, he said lower rates of around 60 to 65kg/ha could be applied in contact with seed.

“ChicKP SZ will better meet the nutrient requirements of chickpea crops and ensure longer term sustainability in the cropping system,” Mr O’Mara said.

“Another strategy to improve potassium supply may be to drill 50 to 100kg/ha of muriate of potash as a test strip eight or more weeks prior to planting.

“This will allow the assessment of potassium responses in chickpeas or other rotational crops.”

Muriate of potash is not recommended for use at planting in contact with seed.

“Alternative organic sources of potassium such as manure and compost can also be used, but they need to be broadcast and incorporated at the beginning of the preceding fallow for seed safety and nutrient availability reasons,” Mr O’Mara said.

“If you’re growing chickpeas where you haven’t grown them before, soil test first to determine starting soil fertility and check for any subsoil constraints.”

Source: Incitec Pivot

 

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