nutrition & flavour: a little hardship helps
Friday 26th April 2013
There have been suggestions in the media that the very wet, dull weather in 2012 has reduced the nutritional value, flavour and yields of vegetables. Some have postulated that organic crops, un-bolstered by agrochemicals, might be more severely affected.
When rainfall exceeds the sum of moisture lost through evaporation (from the surface), transpiration (from plants) and the sponge-like ability of the top soil to absorb water, the excess will percolate through the soil, taking anything soluble with it. Highly soluble nitrogen is lost to the subsoil (out of the rooting zone of most vegetable crops) and eventually pollutes watercourses. Conventional farmers can replace it by adding relatively cheap (hugely carbon intensive), synthetic ammonium nitrate. Organic farmers have to wait for the soil fungi and bacteria to break down complex organic matter to the smaller, soluble nutrients available to plants. Part of the skill of organic farming is balancing the natural release of nutrients with the needs of the crop; we base our plans on an average year, not 2012. Hence it’s fair to say that organic farmers have suffered more in terms of yield this year. Pouring on nitrogen may mitigate yield loss but does not compensate for lack of sunshine and other nutrients and tends to dilute nutrition and flavour.
A little hardship is generally no bad thing. Slower growth can help plants develop their full flavour and improve nutrient content. Some disease fighting chemicals are actually produced as a response to stress or threat. There is often a negative correlation between yield, flavour and nutrient content: the ‘dilution effect’ (the nutritional value of vegetables has fallen by about a third since the adoption of chemical farming in the 1960s). Sunshine is essential, as plants use it to produce sugars. We found flavour a bit dull in the sun-loving lettuce, tomatoes, strawberries and some apples, all of which would prefer to be further south. Cabbage, sprouts, spinach and leeks are happier at our latitude and have been fine. Surprisingly our radicchio was the sweetest I have known.