Pins modernized method application for estimation of arable land soil washout by meltwater (by example ofKrasnoyarsk forest-steppe)

The technique of measurement of washout of soil by meltwater with application of a modernized method of pins is examined.The study was done in 2009 and 2010 on arable lands of the north forest-steppe zone of Middle Siberia (Krasnoyarsk foreststeppe).The territory of Krasnoyarsk forest-steppe includes northern, central, and southern parts. Field researches of washout were conductedin the northern part, which is characterized by many forests. In our researches 40 cm pins were set at a depth of 17-20 cm in theend of winter, their elevated length was measured, and the mark on the pin at the level of the soil surface was made. After the snowmelted to define the size of washout the elevated height of the pins again was measured again. Researches were made at nine structures.Pins were formed in groups and settled down along all the structure of a slope. Each group comprised from two to four pins, their totalnumber was 94 pieces. The distance between pins in group was 10-15 cm. The experimental site, on which the researches were carriedout, is divided into two areas - the northern and the southern ones. The northern area represents weak-convex water-separate surface ofabout 3000 m. long. The southern one is an extensive slope of the southeast exposition. Modernization of the method consisted in thefollowing: for the purpose of the account of swelling an additional pin with a tin plate was been added in each group, skintight to the soilsurface preventing its washout. The pin with a plate fixes only the size of extrusion whereas indications of the other pins also reflect theprocesses of washout. Thus, to define the size of washout it was necessary to subtract the datum from the additional pin from the readoutof each of the core pins in the group. The results of pins measurement after the snowmelt confirm that the pin with a plate, as a rule, isless exposed than the pins without a plate in the group. Significant territorial distinctions in sizes of hydrothermal movements of the soilcover are noted. It can be connected with a various degree of ground turfing, various distributions of thickness of the snow cover andice, and the depth of the soil structure freezing. We shall note that the mechanical structure of the soil at the examined site is heavyloams which are subject to swelling in a greater degree than soils of the light mechanical structure. Thus, modernization of the methodof pins allows applying it to estimate washout of ground from meltwater in the conditions of seasonal freezing of soil cover.

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