Nitrogen-based fertilizers began to be used on a massive scale after the Second World War. Although in a first stage they helped to promote the so-called “green revolution”, the environmental cost was and is enormous.
Artificial fertilizers are often applied in amounts beyond what crops need to grow. The surplus is transported mainly by the effect of rains and irrigation, from agricultural lands to lakes and oceans, producing its eutrophication, the excessive enrichment of nutrients.
To make matters worse, the latest research suggests that climate change will substantially increase this form of pollution, leading to algae blooms and dead zones. This is because heavier rains caused by warmer temperatures will cause more agricultural runoff, pulling more nutrients into rivers, lakes and oceans.
The most comprehensive global study on eutrophication was the Cooperative Eutrophication Program of the Organization for Economic Cooperation and Development (OECD) carried out in the 1970s in eighteen countries (Vollenweider et al., 1980). The sequence of the trophic state, from oligotrophic (poor in nutrients) to hypertrophic (= hypereutrophic [rich in nutrients]) is shown in Table 12 (Control of water pollution from agriculture - FAO irrigation and drainage paper 55).
Role of agriculture in eutrophication
In their summary of the impacts of fertilizers on water quality, FAO / ECE (1991) cited the following issues:
- An explosive growth of algae that causes disruptive changes in the biological balance [including fish kills]. This is true for both inland waters (ditches, rivers, lakes) and coastal waters.
- In all countries, groundwater is an important source of drinking water. In several areas, groundwater is contaminated to the point that it is no longer suitable for use as drinking water according to current standards.
The precise role of agriculture in the eutrophication of surface water and groundwater pollution is difficult to quantify. RIVM (1992), citing Isermann (1990), calculated that European agriculture is responsible for 60% of the total fluvial nitrogen flow to the North Sea, and for 25% of the total phosphorus load.
Appelgren (FAO, 1994b) reported that 50% of shallow groundwater wells that supply more than one million rural residents in Lithuania are unfit for human consumption due to a wide range of contaminants including pesticides and species nitrogen.
In the 1960s, Lake Erie (one of the Great Lakes of North America) was declared "dead" by the press due to high levels of nutrients accompanied by excessive algae growth, fish kills, and anaerobic sediments from the background.
Proper handling of fertilizers
Fertilization is an irreplaceable practice in agricultural activity that consists of replenishing the soil with those nutrients that are depleted by the extraction of the crops itself.
Fertilizers represent one of the main inputs of agricultural production, so their efficient use constitutes an important source of savings and reduction of environmental impacts. There are many sources of information, with resources of good agricultural practices in different crops.
Just as the lack of nutrients in the soil can reduce its yield and fertility, an excessive fertilization, not adjusted to the real needs of the crop, either by quantity, type of fertilizer or time of application, can cause serious problems.
If you intend to start using fertilizers, it is important to analyze your soil. Soils contain all the essential elements that the plant requires for its development and reproduction; however, in most cases, not in sufficient quantities to obtain high yields and of good quality, so it is essential to add the nutrients through fertilizers.
Without the use of fertilizers, the yields will be lower and lower due to the gradual impoverishment of the soil, due to the extraction of nutrients in the crops. An infertile soil produces less, has less vegetation cover and is more exposed to erosion.
Proper handling of fertilizer requires knowing its characteristics, its effect on plants and soil, the forms of application and how it is derived, and how to prepare a dose of fertilization based on available fertilizers. Each plant has different needs, so it is vitally important that it supplies nutrients in forms and amounts assimilable by plants.
You can also choose to use fertilizers that you can get in your home or garden, such as eggshells or ash.