Population growth, changing diets and declining arable land per capita drive growing demand for farmers to find effective ways to increase crop yields. This demand can only be met by increasing the efficiency of agriculture output. It raises a wide range of issues, from the problem of hunger and malnutrition to the sustainable production of safe food that is free from harmful impurities like heavy metals for people all over the world.

Heavy Metals in Soil

A significant amount of research has been conducted into the transfer of impurities like heavy metals from fertilizers to soils and ultimately into the food chain. The extent of the problem, the degree of influence on the human body and potential solutions are the subject of active discussion at many levels (more information in the Health section).

The transferability of heavy metals, such as cadmium, into soils and plants, is complex and influenced by different factors. The type and characteristics of the soil, as well as the plant’s genetics, play important roles in determining the rate of transfer. In general, leguminous crops have the lowest rates of transferability. Cereals, pumpkins and umbelliferous plants (such as parsley and carrots) show a moderate degree of accumulation, while cruciferous vegetables (cabbage and radish), chenopodioideae (beetroot and spinach), nightshade (potato and tomato) and composite flowers (sunflower and chicory) exhibit higher rates [1].

It has been found that heavy metals do not distribute evenly across the plant. As such, the concentration in the main part of the plant may differ from that found in the roots. Limited movement of cadmium from the root system to the plant above ground may be the reason why cadmium concentration found in fruits and grains varies from that in leaves and roots.

The accumulation of cadmium in crops is a result of the close interaction of soil resources, plants and the environment. Cultivation must be done in a way that is mindful of potential sources of heavy metal contamination. Additionally, careful monitoring of human impact on the environment should be encouraged to better understand the factors that contribute to the accumulation of cadmium over a longer period of time.

Food Production

Agriculture has played a vital role in society’s survival and ongoing development. In recent decades, the industry has had to respond to the challenges posed by accelerating growth in population (which has doubled in the last 50 years), changing diets (especially in developing countries), and a reduction in arable land per capita [see figure 1, 2, 3]. To a large extent, this has been achieved through mechanisation, the use of chemical fertilizers and advances in agricultural science. With demand for higher agricultural productivity likely to increase further, careful management of the most important agricultural resources - including soil, water and fertilizers - will become even more important in order to ensure that food supply remains safe and production sustainable.

Chart - Global population, source: World bank
Figure 1: Global population [2].
Figure 2: Meat consumption (beef) [3].
Figure 3: Arable land per capita [4].

Sufficient and Safe Food

Food security refers to people having physical and economic access to sufficient and safe food for their needs. In other words, it involves the consideration of both quantitative and qualitative aspects, with the aim of addressing a wide range of issues, from the problem of hunger and malnutrition, to the provision of safe and nutritious foods that are free from harmful impurities, to people all over the world.

Food production is closely associated with land availability, climate, soil conditions, mechanisation, the use of crop inputs and cultural preferences. In some countries, favourable climates allow farmers to harvest more than once a year (e.g. Brazil), while in others only one harvest is possible. The quality and availability of soil and water are therefore key factors in productivity and yields in different geographies.

Wheat, rice, maize and soybean are the most consumed crops globally. Much of the world’s wheat is supplied by the EU, China, India, Russia and the US. Soybean production, meanwhile, is concentrated in the Americas, where yields are the best. Around a third of all maize is produced in the US, where production is supported by mechanisation and the effective use of crop inputs. Finally, China and India account for more than 50% of global rice production, which is a staple crop in both countries.

Figure 4 - The largest producers of agricultural crops [5].
Figure 5: Crop yield in different regions of the world [6].

Achieving good yields requires an integrated approach to farming, of which balanced fertilization is key. While there are seventeen elements that have been shown to be essential for plant growth, three are required in comparatively large amounts: nitrogen, phosphorous and potassium (N, P and K). Responsible and balanced use of these nutrients has been shown to support efficient crop production and encourages sustainable agriculture.

Along with the pressure to increase yields, a greater focus is now placed on quality and safety of food. Many factors contribute to a healthy diet, and therefore it is necessary to define standards that encourage good practice. Part of this is to restrict the availability of foods that could negatively affect human health. An issue that has resurfaced in recent years relates to contaminants such as cadmium, lead, mercury, arsenic and hexavalent chromium, which have been known to pose a threat to health when exposure levels are too high.

In the case of cadmium, industrial production was formerly a main cause of pollution, but in Europe this is no longer the case as industry has adapted to be more conscious of the environment. Today the main source of cadmium in agricultural soils is phosphate-based chemical fertilizers.

Clearly regulating the use and quality of fertilizers that are applied by farmers to help optimise crop yields is important, yet complicated.

  1. Grant, C. A., Buckley, W. T., Bailey, L. D. and Selles, F. (1998). Cadmium accumulation in crops. Can. J. Plant Sci. 78: 1–17. [return]
  2. Source: The World Bank [return]
  3. Source: OECD [return]
  4. Source: The World Bank [return]
  5. Source: USDA 2015/16 Season [return]
  6. Source: FAOSTAT 2014 [return]

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