Sydney: Researches have devised an inexpensive test to verify whether vegetables have been grown organically or with the help of synthetic fertilisers.

A requirement in growing organic vegetables is that only animal manure be used. As vegetables grow, they incorporate nitrogen from the fertiliser and it is this nitrogen that is analysed.

Nitrogen isotope signatures of animal manure and industrial fertiliser are quite different, according to isotope expert Kryne Rogers.

Rogers said the method was an inexpensive way to distinguishing between vegetables grown with organic or industrially made fertilisers.

"It's an independent check on the growing regime. As far as I am aware, this is the first simple reliable test for organic vegetables," Rogers said.

Clients can obtain results within 10 days of submitting samples, and the test can be done at any stage during vegetable growth. This method can also determine if vegetables are grown hydroponically, or naturally in soil.

A similar isotope technique using carbon can be used to determine if vegetables, such as tomatoes, have been grown in a greenhouse heated by fossil fuels.

Rogers said these new tests were an extension of the food testing his Stable Isotope Laboratory has been doing for the past 12 years.

"Since 1996 we have been testing orange juice for the beverage industry to determine if sugar or tap water has been added."

"We also offer a test for the honey industry to determine if bees have been fed sugar or if glucose has been added to increase the volume of the honey." IANS