How do you know your organic veggies are as labeled? Out of this concern, the The Food Standards Agency in the U.K. "funded a study to come up with a test to confirm the authenticity of finished organic foods." The test uses nitrogen content as a measure. Natural fertilizers like manure leave detectable amounts of nitrogen in crops, while synthetic fertilizers do not. In the test's current form, results aren't stunningly accurate, but it can be used to "support or corroborate the suspicion of trading standards commissions."