Case Study: The Impact of Wetter Soils on Crop Nutrition and Toxicity

North Western Europe has been experiencing a shift in weather patterns leading to increased periods of enhanced precipitation. This has substantial effects on crop nutrition and toxicology.

Oxygen spreads much more rapidly in air than it does in water. Thus wetter and water logged soils alters the soil chemistry by reducing the amount of available oxygen. Any oxygen which is present in the soil under flooded conditions is rapidly used by soil microbes and plant roots, exacerbating oxygen depletion.

Metal(loid)s (e.g. arsenic and silicon) in the soil are sensitive to redox, i.e. the removal of oxygen. Water logging can lead to their immobilization or mobilization greatly affecting the availability of primary trace micro nutrients (e.g. selenium, zinc and copper) and non essential toxicants (e.g. magnesium causes toxicity in crops grown in water logged acid soils).

Anaerobic soil also effects the function of plant roots and may lead to decreased effectiveness of macro element absorption. This is because general metabolic impairment of root function alters the energization or permeability of root membranes. Moreover, the initiation of anaerobic metabolism (i.e. respiration in the absence of oxygen) in roots has additional implications on plant functions through the production of secondary products such as ethylene.

Prolonged water logging will also lead to increased soil compaction as flooded soils are more prone to machinery (e.g. tractors), farming practices (e.g. tillage) and animal (e.g. cattle) damage to the soils structure. This exacerbates anaerobism through further decreases in oxygen permeation.

This systematic reduction in the ability of roots to assimilate plant nutrients has major consequences for the plant through:

• Alteration of flavonoid content

• Toxins such as glycosinolates and glycoalkaloids

• Reduction in macro- and trace element content

Consequently, the flavour and nutrition of crop edible parts are impacted. This makes the plant less palatable or valuable as a nutrient source, or actually makes the plant a potential health risk through the enhanced accumulation of toxins.

What we would like you to do

Please consider the following question in the discussion area below.

• Have you ever considered that the nutritional content of plants and subsequent food products could be impacted by weather conditions, e.g. heavy rainfall?