The temporal dynamics of readily available soil moisture for plants in the technosols of the Nikopol Manganese Ore Basin

Abstract

The restoration of a stable and productive ecosystem after drastic disturbances to the natural environment due to mining and open-cast mining may be achieved by means of reclamation. Investigation of the hydrological budget of technosols is important task in developing adequate approaches to reclamation. Sod lithogenic soils on red-brown clay, on grey-green clay were chosen as the objects of the investigation. The simulation of moisture content in Nikopol Manganese Ore Basin technosols was performed using the Penman-Monteith approach and evaluated the role of the dependence of soils’ surface albedo on the humidity in the intensity of evapotranspiration. The research was conducted during 2013–2015 at the station for research on reclaimed land within the Nikopol Manganese Ore Basin (city Pokrov, Ukraine). The experimental area for the study of optimal modes of agricultural reclamation was created in 1968–1970. Precipitation in the investigated area was found to fall very unevenly in time. In 2013, the duration of the rainless period was 259 days, in 2014 – 264 days, in 2015 – 261 days. The maximum daily rainfall varies within 18–49 mm. There are significant interannual differences in the intensity of rainfall. The minimum total annual precipitation in 2014 was due to a decrease in atypical rainfall in late winter and early winter. The maximum annual rainfall in 2015 was caused by intense rainfall both in the spring and in mid-summer and late autumn. The average annual temperature was 11.1 ºC and the annual totals did not statistically significantly vary within the study period. The average wind speed and average atmospheric humidity are statistically significantly different from year to year. The technosols’ colour properties and surface albedo varied depending on the moisture content. There is a linear relationship between the moisture content in the soil and albedo of the soil surface. The evaluation of readily available water content was carried out based on the Penman-Monteith model taking into account meteorological data, the water-physical properties of the technosols and the dependence of soil surface albedo on soil humidity. The distribution of this index for different teсhnosols is characterized by a high level of similarity of shape due to the fact that the overall climate factors are crucial in shaping the dynamics of moisture. A complex mixture of normal distributions is the best model for representing the experimental data. The readily available water content distribution can best be represented as a mixture of two normal distributions. The relatively high moisture level is characterized for winter and spring periods. Water content in sod-lithogenic soils on red-brown clay over the period of research never reached the value of the permanent wilting point. In 2013, the period when the moisture content was less than the value of the permanent wilting point lasted 23 days, and in 2014 this period lasted 39 days. Thus, you can always expect the phenomenon of drought under typical climatic conditions for the technosols on grey-green clay. It was found that monitoring water supplies before the start of the growing season can provide valuable information necessary for the selection of crops for cultivation in the current year. The results indicate the urgency of measures to save the winter rainfall on the fields.