Although water is essential for each living being, at the same time it is the most common contaminant of land, the environment from which plants acquire dissolved nutrients. Soil pollution by harmful and hazardous substances through water may be from different sources: from mineralized ground water, from particles from the air passed into the soil by rain, through flood and water from rivers which are polluted … And there is also the process of irrigation.
Organic production basically includes plant species that are used in human nutrition in raw condition as well as products that are preserved or processed. These plants produce a huge green mass with a very high percentage of water, with very well developed above-ground mass, and relatively poorly developed root system. For this reason, plants need high quantity of water. By entering large amounts of water, the intake of harmful and hazardous substances are also greater. In this way, harmful substances accumulate in the tissues of plants, which are used as food for humans and animals.
Risk of pollution
The quality of water has significant importance during irrigation in organic food production. However the quality of water is often insufficient because there are different sources of irrigation water: rivers, streams, natural or man-made reservoirs (lakes) and groundwater which is highly contaminated with waste water. In addition to the total quantity and content of certain types of salt, the water quality is affected by chemical substances that come from sewage and pesticides, and by the presence of certain microorganisms.
Many salts and elements are useful for herbs, but to the certain concentration. They are harmful at higher concentrations and pose a risk, both for plants and for animals and humans. The most common elements present in water are calcium, magnesium, sodium and potassium, and from salts: bicarbonates, sulfates and chlorides. Other elements, like nitrates, carbonates and trace elements, in some cases can be found in water and affect water quality. Nitrates in water are required for plant nutrition, but they are toxic to plants in high concentration. Moreover, they are potential groundwater contaminants.