Nutrient supply must match crop demand

Crop demand needs to match nutrient supply


Cropping
BALANCING ACT: SARDI farming systems research scientist Nigel Wilhelm discussed fertiliser and trace elements management at Hart recently.

BALANCING ACT: SARDI farming systems research scientist Nigel Wilhelm discussed fertiliser and trace elements management at Hart recently.

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After a lack of rainfall across the state rapidly depleted soil moisture profiles, nutrient deficiencies in this season’s crops have become the focus of discussions to help improve crop yield in a tough year.

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After a lack of rainfall across the state rapidly depleted soil moisture profiles, nutrient deficiencies in this season’s crops have become the focus of discussions to help improve crop yield in a tough year. 

At the recent Hart Field-Site Group research update, SARDI farming systems research scientist Nigel Wilhelm said growers were concerned about trace element uptake and whether or not the lack of soil moisture meant nutrients were not being accessed by plants. 

“A crop can only extract nutrients from soil that has enough moisture,” Dr Wilhelm said. 

The two nutrients most vulnerable to not being extracted by crops in a dry soil profile are zinc and copper.

“A dry topsoil will highly affect nutrients that will not move through a soil profile, and zinc and copper will stay exactly where they land,” Dr Wilhelm said. 

These trace elements can remain in the top two millimetres of topsoil, making them even more difficult for crops.

“During August and September, if crops are beginning to flower and the topsoil is too dry, copper will not be extracted,” he said.

But growers can respond to the issue by boosting supplies with a zinc or copper foliar spray.

Lower crop yield potential in a tough season has a flow-on effect of lowering demand for nutrients. 

“Unfortunately this season has meant we have not needed a big supply of trace elements because of slow crop growth, they go hand-in-hand,” Dr Wilhelm said. 

“It is a self monitoring situation because if the spring stays dry and the crop potential is low, they have low nutrient needs, which will mean mineralisation will not hurt us too much. 

“In a season like this, it is important to understand why we are putting products out because the crop demand needs to match up with the nutrient supply.”

Dr Wilhelm said regular soil or plant testing to monitor trace elements was vital if growers had doubts about a trace element status or management program efficiency. 

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