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Decreasing soil fertility
Soil acidification
Decreasing organic matter content
Decreasing soil fertility
The main agrochemical parameters of soil are: soil reaction,
organic matter content, nutrient content, and absorption capacity.
According to these parameters, a greater land area of agricultural
is worsening in soil quality than is improving.
Since 1990, the application of mineral fertilizers has declined
by ten times, and of organinc fertilizers by four times. The
present low levels of fertilizer application can not ensure
renewal of nutrients to the soil. However, from the point of view
of environmental protection, the impact of nitrogen and phosphorus
runoff from agricultural land to aquatic ecosystems has decreased.
The concentrations of plant nutrients determine the quality and
productivity of agricultural production. Based on their origin,
soils of Latvia are poor in plant mineral nutrients. Monitoring
conducted between 1993 and 1999 indicated that the available
phosphorus and potassium concentrations decreased in 60% and 70%,
respectively, of the investigated area.
The study results indicate a negative balance of plant
nutrients, and thus a decline in soil fertility. During the past
four years, the total amount of applied fertilizers has stabilized,
but at a relatively low level. An average of 70-80 kg NPK per
planted hectare are applied yearly, but about 35 kg more NPK per
ha/y are removed with production than are applied.
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Soil acidification
The soil reaction is determined by physical features of the
soil, concentrations of plant nutrients and their availability,
and the activity of microorganisms. The optimal soil pH for most
crops is higher than 6.0. Soils with this optimal pH cover only
58% of the agricultural land area. Liming of acidic soils is
required on about 40% of agricultural land /4/. Acidification has
occurred in about 30% of soils.
To prevent soil acidification, yearly about 100,000 ha of
agricultural soils should be limed. Since 1992, an insufficient
area has been limed, which is beginning to affect soil quality.
Increased soil acidity and decreased organic matter content will
lower the availability of nutrients to plants, but will enhance
uptake of pollutants.
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Decreasing organic matter content
Soil organic matter is not only a source of plant nutrients,
but it has also has a big impact on soil physical parameters and
absorption capacity. The mean organic matter content in soils is
1.83%. Monitoring of soils for a period of seven years showed that
the organic matter content had decreased in 24% of the surveyed
area. Soils deficient in organic matter require improvement, by
application of organic fertilizers, mulching, or by growing of
perennial grasses.
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