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UC researchers have developed a way to verify that fertilizers labeled “organic” actually contain ingredients like compost instead of cheaper synthetic compounds.

California leads the nation in organic farms and sales, but confidence in the state's organic produce was shaken in 2008, when major suppliers of organic fertilizer were caught using cheaper inorganic compounds. This prompted the passage of AB 856, which gave regulators more authority over organic fertilizers. However, there was still no good way to test whether fertilizers were actually organic.

Now, based partly on an analysis of 180 commercially available fertilizers and their raw components, UC researchers have developed a relatively simple, inexpensive method for distinguishing organic from synthetic fertilizers. This method assesses N-15, an isotope of nitrogen that is relatively high in organic sources; ammonium, which is relatively low in most organic sources; and the ratio of carbon to nitrogen, which has a characteristic value for a given organic source.

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