Soil depletion
Maize crops drain nutrients from the soil, do not compete well with weeds after the seedling stage and are subject to many diseases and pests. Therefore, the cultivation of high-producing maize requires high fertilizer levels as well as herbicides, pesticides and fungicides, which are deleterious to biodiversity and soil conservation. Heavy fertilizer applications can cause nitrate leaching and soil erosion. Herbicides may contaminate the groundwater while pesticides alter biodiversity (European Commission, 2000). In developing countries, where fertilizers are too expensive for general use, the nutrient uptake is higher than when fertilizers are regularly used, thus reducing soil fertility and causing further soil degradation (CIMMYT, 2009).
Genetically modified maize
The debate about the environmental impact of GM crops is complex and a full discussion of the issue is beyond the scope of this datasheet. GM maize varieties that are herbicide-resistant or pest-tolerant have been commercialised since 1996, and their potential environmental impact has been the subject of considerable debate. Some positive impacts have been reported for GM maize, notably a reduction in herbicide and pesticide use, as well as certain benefits for wildlife (Edwards et al., 2009). However, potential negative effects have also been alleged, including the alteration of the DNA of soil microflora, and deleterious impacts on useful insects, such as butterflies and bees, and on non-GM plants (including maize) through genome transfer (Dale et al., 2002).