O. Vedina : Environmental Assessment and Management in Moldavia
59
During recent years the use of mineral fertilizers in the country decreased
considerably (Table 1) [3]. This decrease is chiefly explained by economic difficulties. These have had an impact on enhancing environmental quality. Improper
transportation and storage, irrational utilization of mineral fertilizers, violating
scientifically determined rates and terms of their application caused negative
environmental impacts. It has been estimated that only 50 % of fertilizers are
utilised by agricultural crops, the remaining portion being lost from the soil
system without benefit for crops. Losses occur through leaching, run-off and
volatilization. It should be noted that main nutritive substances (N, P, K) behave in
quite different ways under use in soils. Nitrogen fertilizers constitute the gravest
threat for environmental contamination in Moldavia. When fertilizers are applied,
nitrogen penetrates into the soil in the form of ammonium, amide or nitrate.
The available moisture leads to the movement of the nitrate nitrogen that has not
been utilised by the plant into lower soil layers which causes a danger of water
body pollution. According to the research carried out in Moldavia on
chernozemic soils, in those locations where fertilizers have been applied for a long
time a significant increase of nitrate content is determined at the depth of 9-10 m,
with 7 to 17 % of nitrogen being leached from the fertilizers. A part of leached
nitrate nitrogen can return into agricultural rotation. It is indisputable that nitrates
at a depth of over 3 m are lost for agriculture. The data received convincingly
prove that in Moldavia nitrogen fertilizers are one of the main pollution sources of
surface and ground waters.
Phosphorus fertilizers are relatively less harmful for the environment than nitrogen
ones. Only a minor proportion of phosphorus fertilizers is leached from the soils
into drainage water since it is immobile in the soils of Moldavia. However, the soil
cover is strongly dissected and most lands are subject to erosion.
Therefore phosphorus absorbed on the surface of soil particles may contaminate
water bodies through soil erosion. The proportion of the agricultural pollution of
waters caused by phosphorus does not exceed 10-15 %. Phosphorus utilization
efficiency from fertilizers is not high, reaching 20 %. The excess accumulation of
phosphorus in soils can lead to its pollution, plant toxicosis, and yield reduction.
Potassium fertilizers do not have a harmful impact on the environment. Potassium
is held sufficiently strongly by chernozemic soils, it migrates slowly and only
small amounts reach drainage waters.
However, together with potassium fertilizers high amounts of chlorine enter the
soil. Chlorine is more mobile and contaminates soils and ground waters through
rapid leaching. Hence, excessive application of fertilizers creates a number of
environmental problems.
Chief among these problems is the contribution of phosphorus and nitrogen
fertilizers to surface water eutrophication, due to which water quality deteriorates.
In addition, the durable application of high doses of mineral fertilizers results in
the accumulation of contaminants in soils, particularly heavy metals, which is an
undesirable phenomenon requiring research and control. According to the
classification of soils by the level of heavy metal contamination some soils on the
territory of Moldavia can be identified as weakly polluted ones [4].
59
During recent years the use of mineral fertilizers in the country decreased
considerably (Table 1) [3]. This decrease is chiefly explained by economic difficulties. These have had an impact on enhancing environmental quality. Improper
transportation and storage, irrational utilization of mineral fertilizers, violating
scientifically determined rates and terms of their application caused negative
environmental impacts. It has been estimated that only 50 % of fertilizers are
utilised by agricultural crops, the remaining portion being lost from the soil
system without benefit for crops. Losses occur through leaching, run-off and
volatilization. It should be noted that main nutritive substances (N, P, K) behave in
quite different ways under use in soils. Nitrogen fertilizers constitute the gravest
threat for environmental contamination in Moldavia. When fertilizers are applied,
nitrogen penetrates into the soil in the form of ammonium, amide or nitrate.
The available moisture leads to the movement of the nitrate nitrogen that has not
been utilised by the plant into lower soil layers which causes a danger of water
body pollution. According to the research carried out in Moldavia on
chernozemic soils, in those locations where fertilizers have been applied for a long
time a significant increase of nitrate content is determined at the depth of 9-10 m,
with 7 to 17 % of nitrogen being leached from the fertilizers. A part of leached
nitrate nitrogen can return into agricultural rotation. It is indisputable that nitrates
at a depth of over 3 m are lost for agriculture. The data received convincingly
prove that in Moldavia nitrogen fertilizers are one of the main pollution sources of
surface and ground waters.
Phosphorus fertilizers are relatively less harmful for the environment than nitrogen
ones. Only a minor proportion of phosphorus fertilizers is leached from the soils
into drainage water since it is immobile in the soils of Moldavia. However, the soil
cover is strongly dissected and most lands are subject to erosion.
Therefore phosphorus absorbed on the surface of soil particles may contaminate
water bodies through soil erosion. The proportion of the agricultural pollution of
waters caused by phosphorus does not exceed 10-15 %. Phosphorus utilization
efficiency from fertilizers is not high, reaching 20 %. The excess accumulation of
phosphorus in soils can lead to its pollution, plant toxicosis, and yield reduction.
Potassium fertilizers do not have a harmful impact on the environment. Potassium
is held sufficiently strongly by chernozemic soils, it migrates slowly and only
small amounts reach drainage waters.
However, together with potassium fertilizers high amounts of chlorine enter the
soil. Chlorine is more mobile and contaminates soils and ground waters through
rapid leaching. Hence, excessive application of fertilizers creates a number of
environmental problems.
Chief among these problems is the contribution of phosphorus and nitrogen
fertilizers to surface water eutrophication, due to which water quality deteriorates.
In addition, the durable application of high doses of mineral fertilizers results in
the accumulation of contaminants in soils, particularly heavy metals, which is an
undesirable phenomenon requiring research and control. According to the
classification of soils by the level of heavy metal contamination some soils on the
territory of Moldavia can be identified as weakly polluted ones [4].