Edyta Hewelke, Jan Szatyłowicz, Tomasz Gnatowski, Ryszard Oleszczuk
Szkoła Główna Gospodarstwa Wiejskiego, Warszawa

Wettability is one of the most important peculiarities of soil and it directly influences their physical, mechanical, chemical, properties biological and their fertility. Soil water repellency can lead to the development of unstable wetting and preferential flow paths. Water flow and solute transport patterns are complex under such conditions. The existence of the water repellent layer can have negative influence on soil moisture content because it reduces the amount of water supplied from ground water level by capillary rise, infiltration from the soil surface and also for retention and therefore acts as a constraint in the restoration of drained peatlands by rewetting. That means that repellency can have significant influence on restoration, conservation and management of the peat resources. The paper presents the result of the spatial variability of soil moisture in a small area in a hydrophobic peat-muck profile located within Kuwasy drainage-subirrigation system at the Biebrza River Valley. Soil moisture variability study was carried out on an area of 1 m2 and 0.5 depth in the two measurement periods. The measurements were made in two versions: the first after artificial irrigation (60 mm) and the second after an intense rain. In both of measuring periods the study area was divided into a regular grid of squares. Spatial variability of the investigated traits was evaluated using parameters of the theoretical variogram and cross variogram models. The variability of soil moisture in the profile after intense rainfall was higher than after irrigation. The maximum range of the spatial correlation (189 cm) soil moisture was observed in the alder peat layer for measurements made after irrigation. The observed variability is associated with high hydrophobicity of studied soil. The observed variability may be important in the assessment of current water resources of the soil profile. The relationship between water content and the surface of the sampling indicates that, following the increase of the sampling surface the dispersion of results gets smaller, and the distributions are symmetric. The relationship between the coefficient of variation CV and the surface sampling shows that most of the variability occurred in the top moorsh layer of soil tested (CV = 40%). To check the stationary conditions for soil moisture measurements, the analysis of the trend were made. Elimination of the trend also provided a normal distribution of residual moisture values. Semivariance and cross variance for residual moisture values were calculated, and then were leveled with spherical or linear model. From the presented data results that after irrigation as well as heavy rain falls there exists the relationship between the distribution of moisture muck individual layers (up to 30 cm) and can be described using a spherical model. The results show large spatial variability of the total variance of soil moisture and poor soil moisture spatial correlation between the different layers of the soil profile.

Słowa kluczowe
semiwariogram, hydrofobowość, gleba torfowo-murszowa

Spatial Variability in Soil Moisture Content under Preferential Flow in Hydrophobic Organic Soil

Key words
semivariogram, hydrophobisity, peat-muck soil

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