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Enlightening Research

Postagrogenic transformation of organic matter in soddy-podzolic soils

Publication Type:

Journal Article

Source:

Eurasian Soil Science, Volume 44, Issue 10, p.1077 - 1089 (2011)

ISBN:

1064-2293, 1556-195X

URL:

http://www.landviser.net/webfm_send/118

Keywords:

anthropogenic, bulk density, ER, LandMapper, organic matter, penetration resistance, sod-podzolic, soil genesis, water permeability

Abstract:

In the chronological sequence of postagrogenic soils, the restoration of the original differentiationof the soil profile and its horizons proceeded with different rates depending on the fallow age and the horizon
depth. The layer sampling (at 5⬚cm intervals) showed that the plow horizon began to differentiate into a sys⬚
tem of subhorizons in all the fallow soils. The zonal pedogenesis showed clear signs of manifestation already
in the 15⬚year⬚old fallow. The upper part of the former plow horizon in the 15⬚ and 60⬚year⬚old fallows under
herbaceous plants was transformed into a soddy horizon, while a postagrogenic soil 90 years old already devel⬚
oped under a zonal type of vegetation and approached the control soil in its morphological features. The con⬚
tent and reserve of carbon in the soils showed a stable tendency of increasing (especially in the upper part of
the plow horizon) during the entire postagrogenic period under study. The water permeability of the soils
gradually increased and approached that of the virgin soil. However, the compacted subsurface horizon (the
plow pan) disappeared only after 90 years. The assessment of the physicochemical properties of the soils and the structural and functional parameters of the humic acids indicated the expansion of the layer differentiation primarily within the homogeneous plow horizon. From the elemental analysis and 13C NMR spectroscopy data, the degree of aromaticity in the molecular structure of the humic acids gradually decreased, and the aliphatic part developed with the age of the fallow.

Notes:

According to Orlov [8], the degree of humification of the organic matter in the soil profile (Table 2) varies
from low to medium depending on the time elapsed since the removal of the anthropogenic load. The lowest value was found for the 15 year old fallow; it slightly increased in the 60 year old fallow, and the
maximum degree of humification was recorded in the upper layers of the 90 year old fallow. The control soil
was characterized by a medium degree of humification.

Original Russian Text © I.O. Kechaikina, A.G. Ryumin, S.N. Chukov, 2011, published in Pochvovedenie, 2011, No. 10, pp. 1178–1192

References

7. Methods of Stationary Soil Studies (Nauka, Moscow, 1977) [in Russian].
8. D. S. Orlov, Soil Chemistry (Izd. Mosk. Gos. Univ., Moscow, 2005) [in Russian].
9. A. I. Pozdnyakov, N. G. Kovalev, and A. D. Pozdnyakova, Electrophysics in Soil Science, Land Reclamation,
and Farming (ChuDo, Tver’–Moscow, 2002) [in Russian].

The value of the electrical resistivity showed that the electrophysical properties of the soils were restored
significantly slower (Fig. 2c). The shapes of the curves for the electric resistivities of the 15 and 60 year old fallows were almost identical, but the parameters of the 90 year old fallow significantly differed from
those of the soils with the shorter restoration periods and the virgin analogue. The control soil was characterized by higher electrical resistivity, which was obviously related to the difference in the bulk densities,
physicochemical parameters, and humus status parameters of the soils. This effect could be due to the preservation of the electroinsulating humus films on the surface of the mineral grains. In the arable soils,
the abrasion of the humus films advanced under the effect of the regular mechanical turbation of the soil,
on the one hand, and the dehumification, on the other hand. However, our data showed that the restoration of
these films was a very slow process.

Under field conditions, the water content of the soil samples was determined by thermogravimetry, the
bulk density of the soils was determined by the cut-in cylinder method, the penetration resistance (by
micropenitrometer MB-2) and water permeability (by the tube method) were determined according to
[10], the electrical resistance was measured with a LandMapper instrument [9], and the basal respiration
(СО2 emission) was measured by the Shtatnov method [7].