S.V. Obushchenko
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Summary. The analysis of dynamics of the main indices of soil fertility and agroecological situation of the used agricultural lands for 50 years as well as atmospheric condensations and vegetation showed that the weighted concentration of humus in soils in Samara region reduced for the period of observation by 1.16 %. At that, the portion of soils with low and very low humus content increased 2.2 times (from 19.3 to 43.3 %), with increased and high content – reduced 2.8 times (from 33.8 to 11.9 %). During the first four cycles of agrochemical inspections the weighted average amount of available phosphorus grew and reached maximum in 1986-1991 (100.5 mg/kg of soil), after that it began to come down. By 2012 the value of this index reduced to 94.8 mg/kg of soil. In this case during the years of observation the portion of soils with low and very low content of available phosphorus decreased 2.7 times (from 41.5 to 15.4 %), with increased and high one – raised 2.2 times (from 6.6 to 14.1 %). The weighted mean content of exchange potassium in all these years was characterized as high and varied at level 123.2…158.3 mg/kg of soil. The maximum value of this index was in 1969-1975. The soils of the region have sufficiently stable indices in microelements content, they are characterized by harmless content of heavy metals and radiological background. The obtained plant production does not accumulate a dangerous quantity of toxic substances and can be used for food and feed purposes. The falling out precipitations also do not have a negative effect.
Keywords: soil, fertility, dynamics, humus, phosphorus, potassium.