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aggregation rate (indicator defining water stability of microaggregates) 2.3 units to 29.8 units.
The increased soil moisture was also due to a very large water absorption capacity of peat.
One kilogram of bone dry peat can absorb and retain from 5 to 30 kg of water (Tishkovich,
1993).
Figure 7. Effect of mulches on the content of productive moisture in the plow horizon.
Mulching with bentonite clay had a similar effect on the retention of productive moisture
to that of peat. It exceeded the control by 16.6%. This was due to the fact that the minerals
contained in clay had a good structure-forming and moisture-retention capacity. Adding 8 t/ha
of bentonite clay to the top of the plow horizon reduced its dispersion factor (indicator that
determines the strength of the microstructure) from 28.3 (in the control) to 22.0 units,
increased the aggregation rate from 2.3 to 25 units and increased the particle-size index of
structural properties (indicator showing the potential ability of the soil to form structure) from
7.7 to 7.9 units.
Mulching with straw showed good results in terms of productive moisture retention,
exceeding the control by 12.4%. This effect was caused by a number of reasons. First, soil
permeability grew by 10-25 %, which decreased runoff dramatically. Lack of soil crust and a
higher layer of water on the soil surface resulted in accelerated infiltration. Secondly,
applying straw to the surface reduced evaporation since it had lowered the speed of the
surface wind, the soil temperature and the water vapor diffusion resistance. Third, on clear
days we observed surface and subsurface dew under the mulch of straw. According to A. N.
Kashtanov (1974), during the growing season dew can accumulate up to 85 mm of additional
water in the soil.
The ability of post-harvesting residues used as mulch to reduce evaporation significantly
was noted by many authors (Klocke Stock et al., 2009; Bagirov 2011, etc.). It should be
mentioned that this ability of straw to reduce unproductive evaporation was gradually falling
with its greater mineralization and was statistically valid only for two years.
Limestone powder had the smallest impact on the content of productive moisture in the
plow horizon, exceeding the control by only 4.6 % on average at a middle confidence level.
The effect of lime on moisture retention is based on the improvement of the structure of the
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