Structure is a key soil characteristic which directly and indirectly influences the entirety of processes in soil, especially water and solute transport, plant growth, or microbial degradation of pollutants. Comprehensive scientific efforts are made to develop and establish models which describe these processes and allow predictions of process rates and future scenarios. Most implementations of such models in software products treat soil structure as being constant, even though it is known that considerable alterations occur therein. Especially at sites under heavy human utilization pressure, soil management measures affect the stability of soil aggregates and hence the rate of structural changes like compaction or incrustation. On the other hand, certain changes in land-use or soil management strategy can stimulate soil biotic communities which enhance the formation of stable structural elements. Thus, some basic predictive models for the evolution of soil structure, especially soil pore distribution, are already published, but were derived from a very small data basis.
In the last years, innovative lab and field methods reduced the time requirements for the investigation of hydraulic soil properties substantially compared to the methods used for initial model development. Hence, it is now possible to evaluate or renew modelling approaches for a broad range of soil management strategies based on high frequency measurements. In this study, pF-curves (soil water content and hydraulic conductivity, respectively, as functions of matric potential) are the core instrument for the description of hydraulic soil properties. Three methods are combined for their determination: a hood infiltrometer for the field-saturated and near-saturated range, the evaporation method for medium moisture and dewpoint potentiometry for the dry range.
Moreover, the alterations in soil structure will be quantified following two slightly different main approaches and the actual experimental design for both contributing countries, Germany and Austria, is synchronized to allow optimal comparability. The first sampling strategy is applied at cropped fields and the focus lies on the influence of soil management strategy on the seasonal patterns of structure alterations. Three treatments are examined: no-till, reduced tillage, conventional tillage and the measurements will be conducted every 3-4 weeks during the vegetation periods. The other approach aims at mid-term changes in soil structure after land-use conversions. Experiments are planned in afforestations of Christmas trees and poplar plantations for energy usage in Austria as well as typical oak forests in Germany, respectively. As the former fields were only partly converted, the original state is still observable and an artificial time series approach will deliver estimations of the alteration rates over years or few decades. The examined Austrian sites are located in the Lower Austrian villages Pyhra and Hollabrunn and managed by agricultural technical schools which conduct several long-term soil management experiments there. In Germany the experiments will take place on areas of an agronomy enterprise which also launched soil management experiments more than a decade ago.
As a result of this study, ready-to-use modelling approaches will be provided and the implementation into state-of-the-art software will be examined and proposed. Therefore, appropriate predictive variables will be examined in comprehensive analyses of the soil samples and climatic data. The main tasks and responsibilities in this project are shared amongst the project partners, the actual modelling and analyses of the mid-term changes should be primarily treated in Dresden, analyses of the short-term alterations in Vienna.