Vasinauskienė, R. and Šilingienė, G. 2016. Temperature Field Distribution Character in the Upper Soil Layer of Forest Nurseries after Water Steam Treatment. Baltic Forestry 22(2): 297-­306.

   Ecologization of agriculture and forestry directly and indirectly influences the environment, water, air, and landscape. Therefore, analysis of ecological forestry activities, evaluation and forecast are of scientific, ecological and political significance. Weed control and the resulting ecological farming and forestry issues have attracted greater attention to the use of physical methods in weed control, because this weed control method is effective and does not leave chemical residues neither in the soil, nor in water. One of the physical methods is thermal weed control method, which contrary to the other weed control methods, leaves only dead biomass, preventing self sowing of weed seeds in the soil, destroys some of the pests and disinfects the surface layer of soil. However, it is very important to examine the possibilities of wet water steam dispersion in soil. The aim of the study was to determine temperature field distribution character and intensity in the upper layer of the inter-beds soil in forest nurseries. All analyses were carried out using air-dry soil (Calc(ar)i-Epihypoglevic Luvisol, LVg-p-w-cc(sc)) passed through 1.7 mm sieve. Temperature field distribution character and its intensity in the upper soil layer was registered using 0.19 mm diameter nickel­chrome thermocouples, arranging them in the measuring planes according to the measuring schemes prepared in advance. The change of temperature field was registered using Almemo device. Study results showed the dependence of temperature field distribution character and intensity upon the duration of wet water steam supply, steam amount and overpressure under the cover. The data showed that weed seedlings in the depth of 0.5–2.5 cm would be killed treating the soil with wet water steam for 30­60 seconds. The results of the analysis provide a possibility to supplement the common existing weed control system using wet water steam with additional technology – weed seeds control in the upper soil layer.

Keywords: weed seeds, the upper soil layer, water steam, temperature field.