Herbicides impact flavour and nutritional value of food crops

The use of herbicides in agriculture can cause subtle biochemical changes in treated food crops, according to university researchers.

An investigation led by Clemson University and University of Tennessee horticulturalists Dr Matthew Cutulle and Dr Greg Armel conducted a comprehensive series of trials on large sweetcorn fields.

The team analysed the impact on the flavour and nutritional value of the sweetcorn after using four herbicides: mesotrione, topramezone, nicosulfuron and atrazine. The researchers also sprayed some sweetcorn crops with isoxadifen-ethyl, a common herbicide safener that protects the crops from herbicide damage. On other occasions the herbicide was used without a safener.

“Crops can survive systemic herbicidal applications through various forms of detoxification, including metabolism that can be enhanced by safeners,” said Dr Cutulle in the article, published in the Journal of Agricultural and Food Chemistry.

The researchers conducted the experiments by first planting sweetcorn in plots in two locations. After the plants had reached 5cm–10cm, they were exposed to one of seven herbicide safener combinations.

For the scientific control, one field was sprayed with atrazine before the sweetcorn was planted. Had the investigators used no herbicides at all for the control, the crops would have been destroyed by weeds. The sweetcorn was harvested after 45 days and the fully formed kernels were tested based on their levels of antioxidants, sugars, amino acids, proteins, fatty acids, minerals, and fibre.

The results of the experiment revealed that herbicides increased the level of protein in kernels by 4%-12% and the level of minerals by 14-51% under the nicosulfuron/safener combination. Iron content of kernels increased by 67% in crops exposed to this combination.

Examining the balance of sugars, the researchers found the levels of fructose concentrations in the crops rose by 48% when exposed to nicosulfuron, 63% for topramezone, and 68% for the nicosulfuron/isoxadifen-ethyl combination.  The increases of glucose concentrations in kernels amounted to 19% (mesotrione), 40% (topramezone) and 43% (nicosulfuron combination). However, sucrose levels dropped across the board.

According to Cutulle, the specific effect these chemical changes have on flavour is not confirmed, however they could be substantial enough to have a noticeable impact. The researchers plan to use taste experts to undertake further experiments into this impact.

The findings prove that herbicides can change nutritional composition of crops. Observing iron-enhancing properties, for example, could help food producers to develop specific products for people suffering from iron deficiencies, which can result in serious illnesses such as anaemia. On the other hand, high concentrations of fructose can lead to fatty liver disease and diabetes.

With more farmers turning to herbicides to manage commercial demand for food products, the debate is growing over whether organic farming–using no pesticides at all at the expense of a lower yield–is a better approach.