One of the reasons of abandoning of traditionally cultivated Crops is the presence of chemical fertilizers that are used to increase crop quantity and quality and to influence the taste of many cultivated food. In fact, there is an increasing environmental concern about food-related illnesses connected to the use of these chemicals.
The major trouble with chemical fertilizers is the nitrate contamination of food that could lead to nitrate poisoning to both human and livestock. The tendency for food contamination is high for short-cycle crops like vegetables and maize, root crops like carrots and tubers like yams and cassava. But, this depends largely on the type of fertilizer application, the quantity and rate of application.
Many studies revealed that above 5% of nitrogen nutrient from fertilizers application is passing to water during the cropping season. Two-thirds of it is due to the inappropriate application.
Unfortunately, most farmers carry out mix application of agrochemicals, where liquid pesticides are often mixed with either powder or liquid chemical fertilizers during application. This makes identification and characterization of the risks of inorganic fertilizers on soils and food crops a difficult task and needs more research and investigations.
Chemical fertilizers exist as solid granules and as concentrated powders and are applied either as solid granules or as soluble solutions to plants. Application largely depends on the method of application, types of plants, field management, timing and existing soil fertility.
The application of chemical fertilizers to plants can either be direct application, via intention farming like irrigation or indirect via atmospheric processes from rain pollution.
Whatever the application type is, this leads to corrupting soil properties and then the tendency for a destructive soil health would be inevitable. Although chemical fertilizers such as phosphorous, sodium nitrate boost crop production, their overuse and increased application have caused different problems to soil health. These include soil hardening, decreased fertility and strengthened pesticides.
Some fertilizers do not dissolve in water, and its overuse may cause soil hardening. Also, overapplication of fertilizers increases soil alkalinity and reduces its fertility and makes it barren. Soil fertility and crops development depend much on the balanced supply of essential soil nutrients and minerals. As such, overuse and/or application of specific nutrients may cause nutrient imbalance. This can result in soil degradation and the loss of soil nutrient equilibrium in a stable soil.
Food contamination rate vary from short-cycle food crops to mid-cycle, annual, root crops and perennial crops. Perennial crops have well-established root systems and patterns, and their uptake of nutrient is slower over a longer period of time. They can effectively absorb nutrients for the development of fruits, nuts and leaves over prolonged periods of time.
Generally, plant nutrient uptake is highest during the vegetative growth stage of plants. This implies that for short-cycle crops, the uptake of fertilizer nutrients is higher and shorter than for annual and perennial crops.
For root crops like carrots, yams, cassava and cocoyam, the uptake and accumulation of nutrients from natural and conventional sources can also be faster and higher, because their roots are the major storage of needed food. This indicates that a high amount of chemical fertilizers on short-cycle and root crops can be problematic when considering the determining factors such as the quantity and rate or time between one application and the other.
Health problems associated with chemical fertilizers have been most recorded after the consumption of vegetable than with other types of crops. The most common types of food contamination-related illness are Diarrhea and stomach-ache.
Other studies noticed different diseases caused by nitrates, for examples alimentary canal tumours, leukaemia and methaeminoglobinaemia for newborn babies as small children and elderly people. Methaeminoglobinaemia is mostly associated with nitrate-polluted water, and occurrence of this disease is now rare.
Nitrates from chemical fertilizers are not very harmful for humans, but they are transformed into very toxic nitrites in the body by intestinal microflora to nitrites which are 6 to 10 times more toxic.
The global need of chemical fertilizers to increase food production and crops quality may be inevitable as the world population continues to increase and challenges of food security become a major issue for many poor nations. But, the use and the application of these chemicals shoud be modulated and well-controlled.