EFFECT OF VARIOUS MULCH MATERIALS ON SOD-PODZOLIC SOIL AND FIELD CROPS YIELD - Fertilizers: Components, Uses in Agriculture and Environmental Impacts - page 271

Figure 6. Effect of mulches on the content of exchange potassium in the plow horizon.
Incorporating straw in the soil layer of 0-5 cm increased the content of labile phosphorus
by the average of 6% and the content of exchange potassium by the average 3% during the
five years (Figures 5 and 6). These elements were released in the process of mineralization of
straw's organic matter. Unlike peat, this effect of straw lasted only two years. Besides, its
application even reduced the amount of labile phosphorus and potassium in the plow horizon
at first. This is explained by the immobilization of these elements by the decomposing
microflora. The substance subject to particularly strong immobilization was nitrogen, the
amount of which was in most cases lower than in the control throughout the observation
period.
Mineral mulches (bentonite clay and limestone powder) also increased the content of the
exchange potassium and especially labile phosphorus in the plow horizon. However, this
effect was less marked, and it was only due to the improved nutrient status of the soil.
3. Effect of Mulches on Physical Properties of the Soil
The study has found a comprehensive positive effect of mulches on all major
agrophysical soil properties. Mulching can restore natural water-regulating mechanisms
affected by plowing. Mulch, in a broad sense, acts as А 0 horizon (plant litter or sod) of virgin
soils. Mulch passes water very well and prevents the draining of the topsoil. So it increased
the stocks of productive moisture in the plow horizon. The greatest effect in this respect was
produced by peat  on average it exceeded the control by 17.7% during the five years (Figure
7). The positive effect of using peat as mulch was determined by the fact that it formed a
loose well-structured layer on the top of the plow horizon. Mixing 40 t/ha of peat with the soil
layer of 0-5 cm reduced the density of this layer by the average of 5-6% (from 1.281.32
g/cm3 in the control to 1.201.26 g/cm3 when peat was applied) and increased the