Deficit Irrigation

Can less water mean tastier herbs?

We all love fresh herbs for cooking – but are they sustainable? Latest research shows that the water footprint of potted herbs can be reduced and at the same time, flavour and quality improved

For many of us from northern climates, old enough to remember, adding herbs to a favourite dish was about opening a jar and sprinkling in some ageing dried leaves. They didn’t really taste of much. Then a revolution happened on our supermarket shelves – beautiful fresh, tasty plant pots of growing basil, coriander, parsley that lasted long enough to give us the smells and tastes of warmer climates and a pot to brighten our kitchen window sill. No wonder the market growth in such herbs has been in double digits for several years, bucking the trend in food sales.

Deficit Irrigation

But are potted herbs sustainable?

Potted in peat and sold in plastic pots and wrappings – there is much to do to improve this supply chain. But at least for the UK, they tend to be grown under glass, with limited food miles. The latest research suggests there is also significant potential to reduce the amount of water used in irrigating these crops, which must be good for the environment. A massive 70% of global freshwater abstracted is used in crop irrigation. In the future we expect irrigation water will become more and more limited as demand for food production increases and climate change leads to altered patterns of rainfall. The concept that plants can thrive if given less than optimum amounts of water during irrigation, termed ‘deficit irrigation’ isn’t new, but deployment of this approach in herb crops is limited.

Rowland and colleagues (2018), have reviewed the available information and show clearly that deficit irrigation can be used for several herb crops including basil and parsley. Surprisingly, despite the water restriction, the quality of the herbs can actually improve, with more essential oils for aroma and flavour and increased anti-oxidants, particularly phenolics and vitamin content. These are thought to be linked to some of the health benefits associated with eating leafy greens.

The message seems clear, using less water can provide multiple benefits for herb production – for the environment, for the growers, as the price of water rises and to the consumer – delivering herbs of even better quality. Now we just need to fix the plastic pots and this really will be a super-food.

Gail Taylor

Gail Taylor, a professor and chair of the Department of Plant Sciences, specializes in plants, genetics and the environment. Taylor completed her Ph.D. from Lancaster University, UK, and served as both a professor and director of research for Biological Sciences at the University of Southampton, UK, before joining the faculty at UC Davis in 2017.

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