Scientists have advised farmers to thoroughly check nutrient levels in fertilisers before they lay out cold hard cash.

NSW Department of Primary Industries soil chemist, Mark Conyers, said agronomists had contacted him with concerns about low nutrient levels in some fertiliser products.

"There are some products which are delivering $50 worth of nutrients at a cost of $700," Dr Conyers said.

"Just because a product is cheaper doesn’t make it a bargain, especially if it fails to deliver adequate nutrients to crops.

"Some labels use percentage rates while others may use milligrams per kilogram, farmers should convert back to percentage rates to compare products and make sure they are getting value for their dollar."

Growers can compare the price per unit of nitrogen or phosphorus to calculate the true cost of their fertiliser.

Urea can be used to standardise the price of nitrogen (N) and gypsum used to standardise the price of sulphur (S).

If urea costs $600 per tonne and is 46 per cent N or 460 kilograms of N per tonne of urea, then the cost of N is $1.30 per kilogram.

Gypsum with 15 per cent S which is $60 per tonne spread, would cost $0.40 per kilogram.

Handling ability of the fertiliser, soil moisture and nutrient levels, rain and nutrient availability are all factors farmers need to take into account when choosing which fertiliser will best suit the needs of next season’s crops.

Two poor seasons have meant growers have not extracted as much fertiliser out of the paddocks and could have substantial carryover fertiliser.

Growers can use yields to calculate the amount of nutrient extracted and workout fertiliser requirements depending on paddock history and soil test results.

Contact your NSW DPI district agronomist.