B. Usowicz

Comparison of surface soil moisture from SMOS satellite and ground measurements

Abstract Soil moisture datasets at various scales are needed for sustainable land use and water management. The aim of this study was to compare soil moisture ocean salinity satellite and in situ soil moisture data for the Podlasie and Polesie regions in Eastern Poland. Both regions have similar climatic and topographic conditions but are different in land use, vegetation, and soil cover. The test sites were located on agricultural fields on sandy soils and natural vegetation on marshy soils that prevail in the Podlasie and Polesie regions, respectively. The soil moisture ocean salinity soil moisture data were obtained from radiometric measurements (1.4 GHz) and the ground soil moisture from sensors at a depth of 5 cm during the years 2010-2011. In general, temporal patterns of soil moisture from both satellite and ground measurements followed the rainfall trend. The regression coefficients, Bland-Altman analysis, concordance correlation coefficient, and total deviation index showed that the agreement between ground and soil moisture ocean salinity derived soil moisture data is better for the Podlasie than the Polesie region. The lower agreement in Polesie was attributed mostly to the presence of the widespread natural vegetation on the wetter marsh soil along with minor contribution of agriculturally used drier coarse-textured soils.

Biological activity and microbial genetic diversity of bare-fallow and grassland soils

Microorganisms and their interactions with plant and soil provide soil environment integrity. The structural and functional diversity of microbial population in soil is necessary to maintain resistance to environmental perturbations. The aim of this study was to compare metabolic activity and genetic diversity of soil microbial communities at different depths under two soil managements. The experiment included five following soil objects: GR20 – rhizosphere from grassland (0–20 cm), GNR20 – nonrhizosphere grassland (0–20 cm), GNR40 – nonrhizosphere grassland (30–40 cm), BF20 – bare fallow (0–20 cm), BF40 – bare fallow (30–40 cm). Metabolic activity was assessed by dehydrogenases activity and community level physiological profiling using EcoPlates. The study also included genetic diversity assessment, with the use of denaturing gradient gel electrophoresis to reveal genetic structure of ammonia-oxidizing bacteria (AOB). The results showed that soil metabolic and biological activity decreased with soil depth and decreased in bare fallow objects. Highly utilized substrates in both management systems belonged to compounds of microbial biomass. These microbial substrates were amino acids, especially l-asparagine, and fungal substrates were mannitol and N-acetyl-d-glucosamine. In grassland soil highly degraded substrates additionally included d-cellobiose and d-xylose, which are compounds of plant cell walls. Analysis of genetic differentiation among treatments showed unique AOB structure in soil rhizosphere. This was mainly caused by the availability of roots exudates, including amino acids and carbohydrates.

Spatial relationships among cereal yields and selected soil physical and chemical properties

Sandy soils occupy large area in Poland (about 50%) and in the world. This study aimed at determining spatial relationships of cereal yields and the selected soil physical and chemical properties in three study years (2001-2003) on low productive sandy Podzol soil (Podlasie, Poland). The yields and soil properties in plough and subsoil layers were determined at 72-150 points. The test crops were: wheat, wheat and barley mixture and oats. To explore the spatial relationship between cereal yields and each soil property spatial statistics was used. The best fitting models were adjusted to empirical semivariance and cross-semivariance, which were used to draw maps using kriging. Majority of the soil properties and crop yields exhibited low and medium variability (coefficient of variation 5-70%). The effective ranges of the spatial dependence (the distance at which data are autocorrelated) for yields and all soil properties were 24.3-58.5m and 10.5-373m, respectively. Nugget to sill ratios showed that crop yields and soil properties were strongly spatially dependent except bulk density. Majority of the pairs in cross-semivariograms exhibited strong spatial interdependence. The ranges of the spatial dependence varied in plough layer between 54.6m for yield×pH up to 2433m for yield×silt content. Corresponding ranges in subsoil were 24.8m for crop yield×clay content in 2003 and 1404m for yield×bulk density. Kriging maps allowed separating sub-field area with the lowest yield and soil cation exchange capacity, organic carbon content and pH. This area had lighter color on the aerial photograph due to high content of the sand and low content of soil organic carbon. The results will help farmers at identifying sub-field areas for applying localized management practices to improve these soil properties and further spatial studies in larger scale.