Agrogenic transformation of soils in the dry steppe zone of the Republic of Kazakhstan

We present the results of monitoring investigations of agrogenic temporary transformation of humus parameters, volume weight, total nitrogen and phosphorus in the arable horizon of dark chestnut carbonate light argillaceous and heavy argillo-arenaceous soils in the transition from the deep subsurface to shallow minimum tillage and direct seeding. We carried out monitoring investigations of agrogenic soil transformation in the dry steppe zone on arable lands of Akmola region, which were represented by 10 permanent ecological plots. We analyzed soils according to the following types and methods: humus by Tyurin in Simakov's modification, total nitrogen by Kjeldahl, total phosphorus by Ginsburg and bulk density by Kachinskii. At present, dark-chestnut soils in the dry steppe have a pronounced tendency to deterioration of physical properties of soils in the transition to minimal tillage and direct seeding and in this case, the equilibrium density in the 10-25 cm layer goes often in a strong degree of compaction and reaches 1.45 g/cm ³, which ultimately leads to reduced grain yields. Grain yields decrease with bulk density increasing, which shows a close relationship of productivity of agricultural crops with soil density. Quantitative evaluation of changes in the humus and the total phosphorus in the upper horizon of dark chestnut arable soils shows the unevenness of its distribution in the arable horizon during the soil processing transition from deep subsurface tillage to minimum tillage or direct seeding. In terms of time dark-chestnut carbonate light argillaceous and heavy argillo-arenaceous soils there is a tendency to a decrease in the arable horizon percentage of humus, total nitrogen, and, to a lesser extent, total phosphorus. Traditional humus content of subsurface soils in the arable horizon in the layers 0-10 cm and 10-25 cm is approximately in equal quantitative terms, while, minimizing processing, there is some inhibition of organic matter mineralization in the layer 0-10 cm and ranges from 1,93% to 2,98%, as in 2003-2006 and in 2011-2013. In the 10-25 cm layer, during a long absence of mixing in the soil, while minimizing processing, we noticed a decrease in humus from 1,892,90% in 2003-2006 to 1,54-2,71% in 2011-2013. We observed the same trend with the content of total nitrogen and total phosphorus in the 10-25cm layer and during a comparative analysis of data for 2003-2006 and 2011-2013 the reduction was 0,010,02%. We conclude that soils in the dry steppe zone of Kazakhstan experience intense human pressure in the transition to a smaller minimum and zero tillage of heavy granulometric soils, which leads to even greater soil degradation and pronounced separation of the arable horizon in humus percentage and other parameters of soils productivity.

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