Ask an Expert: what happens to fertiliser in a drought year?

Author: | Date: 04 Sep 2018

Image of dry conditions
The GRDC’s online ‘Ask an Expert’ section, which brings together a range of expert grains researchers and advisers at, has been fielding queries about the impact of the ongoing dry conditions. Photo: GRDC

If you are a grain grower struggling with drought conditions and wondering what happened to the fertiliser you applied this season on a crop that failed, the Grains Research and Development Corporation (GRDC) has experts to answer your queries.

The GRDC has just launched an innovative, online community website, which brings together a range of expert grains researchers and advisers together online ( to share information, knowledge and technical advice on seasonal issues to improve on-farm profitability.

The ‘Ask an Expert’ section of the site is rapidly gaining traction amongst Queensland and New South Wales grain growers and agronomists as a key place to go for expert guidance and information on issues such as paddock nutrition in drought affected areas.

GRDC Communities Nutrition Leader Tony Cox from the NSW Department of Primary Industries (DPI) said in recent weeks the community had been fielding queries about the impact of the ongoing dry conditions on elements such as applied fertiliser and residual herbicide.

“Grain growers and advisers are coming to the website and our social media sites, because they can ask their questions and get measured, informed advice back from a group of experts in a short time-frame,” Mr Cox said.

“And our experts are keen to help and support grain growers and their advisers any way we can, especially in areas hit hard by drought.”

He said an example of a recent ‘Ask an Expert’ query from a grain grower was:

Grower question: We are struggling with drought and were wondering what will happen to the fertiliser we applied this year on a crop that has failed. We applied 70kg of MAP and 25kg of Urea pre-plant on wheat sown at 40kg a hectare on minimal moisture. We have placed the sheep on the crop for feed. Will there be fertiliser still in the soil? What happens to the nitrogen mineralisation rate if it’s dry and warm?

Expert answer: Our experts suggest that essentially the phosphorus will still be there, along with some of the nitrogen. Grazing livestock will not remove much phosphorus, but some nitrogen in the grazed material may be lost as volatilisation from urine patches rather than recycled.

Nitrogen mineralisation rates will slow considerably. Mineralisation requires warm temperatures and moist soils – so it will be slow unless there are some spring/summer rains to speed things along. Soil testing prior to the next crop will be very important to determine soil reserves and for nutrient decision making. The following links may provide some additional information for you:

GRDC Grower Relations Manager North, Richard Holzknecht, said the GRDC Communities website had brought together two highly regarded information sites, Crop Nutrition and Field Crop Diseases, along with other grains industry experts.

“What we wanted to create as part of GRDC Communities was a central environment where experts, agronomists, researchers and grain growers from any region could discuss, develop, publish and share information that is important to the grains industry,” Mr Holzknecht said.

“The ‘Ask an Expert’ initiative provides an independent voice to growers and advisers, along with rapid access to technical advice and information.”

Within the GRDC Communities website, the Crop Nutrition community is operated by New South Wales Department of Primary Industries (NSW DPI), while Agriculture Victoria will oversee the Field Crop Diseases community.

For more information or to ‘Ask an Expert’ for advice on issues impacting your crop go to

Contact Details


Richard Holzknecht, GRDC
0408 773 865


Toni Somes, GRDC
0427 878 376