While the various negative impacts of cadmium exposure on human health are now more widely recognized, there has been less discussion on how the presence of cadmium in soils actually diminishes the output of some of the world's most important agricultural produce. While reliance on wheat and rice as two of the world's primary food sources is set to increase by 13% in the period between 2018 and 2027, climate change is already affecting yields for these crops, with estimated annual falls of 0.9% and 0.3% respectively. This stark reality is being exacerbated by the unnecessary presence of cadmium in agricultural soils, which is largely due to the use of contaminated fertiliser products.

Effect of Cadmium Stress on Wheat Yield

The presence of cadmium in agricultural soils causes several types of damage to the growth of wheat: it will inhibit plant growth, impede nutrient uptake, reduce plant respiration and photosynthesis, and lead to a decrease in wheat yield.

Zhu et al. (2012) demonstrated that cadmium may damage the transportation pathway of organic materials absorbed or "assimilated" by the plant during the process of grain filling, resulting in the failure to transport the assimilated material into each grain. This leads to the remnants of the assimilate material staying in the leaves and stem sheaths, which effectively chokes the plant and leads to a decline in wheat yield. Yang et al. (2011) showed that cadmium stress significantly decreased wheat yield, with the number of spikelets, grains per spike, and 1000-grain weight proportionally decreasing with the increase of cadmium concentration. It is also speculated that cadmium will affect the fertilisation process of wheat, resulting in the incomplete development of sexual organs and the formation of hollow grains, and it may also lead to pollination failure.

Effect of Cadmium Stress on Rice Yield

A study by Chen et al. (2013) showed that the accumulation ratio of cadmium in different plant organs led to a number of different factors affecting yield, including plant height, ear length, spike number, seed setting rate, 1000-grain weight, and real grain number. Huang et al. (2008) thought that the main reason for the reduction of yield in cadmium-affected rice was the reduction of panicle (flowering shoot) numbers, and grain numbers per panicle. Similarly, Zhao et al. (2006) showed that the reason for the decrease in rice yield was that the number of grains per panicle was reduced. Additionally, soybean, corn, and rapeseed crops have all exhibited similar reductions in yield under cadmium stress. Many studies have shown that a high concentration of cadmium seriously affects the stability of crop-yield traits, which leads to a significant reduction in production volumes.

These negative effects on crop production caused by cadmium are clearly inconsistent with the sustainable food production objectives outlined in the EU's Farm to Fork Strategy. With another of its key goals being to optimize the use of plant protection and fertiliser inputs, the EU must address this issue of contaminated products aggravating agricultural losses as the climate emergency continues to escalate.

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