One of the major challenges of the 21^st century is the mediation of climate change through the sustainable management of natural resources. Soil organic matter (SOM) together with water holding capacity (WHC) is known to play a key role in productivity changes of land use.  The envisioned project is aimed to better understand the relationship between WHC and SOM in dependency on different land use.

The planned approach is based on traditional knowledge and methods describing the dependency of WHC on soil texture and soil management, with an evaluation of new opportunities to assess the SOM status via simple thermogravimetric analyses. This will help to:

1. a) Quantify the interdependency of WHC from texture, SOC and other impact factors more accurately,
2. b) Make a prediction of WHC for practical soil use possible, and
3. c) May improve SOM assessment or help to validate the informative value of current SOM assessment via relationship to WHC.

The study will focus on secondary data evaluation of samples from different fertilization plots of long-term field experiments, long-term monitoring areas, soils under forestry, horticulture use and of another origin. Since a large portion (approximately 90%) of SOC occurs in aggregates, an investigation of the SOC fractions as well as mineral-incorporated organic carbon (MSC), intra-particulate organic carbon (iPOC) and microbial biomass carbon (MBC) will conduct in bulk soil and water-stable aggregates as influenced by soil fertilization managements in different soil textures, using three treatments: no fertilizer (C), chemical fertilizer (F) and organic manure (OM). It will be used to validate found relationship between soil texture, WHC and SOM status and based on detectable changes in WHC and SOM during long-term laboratory incubation experiments.

The results are expected to reveal quantification and prediction opportunities of long- and short-term dependency of WHC on main impact factors (soil organic matter, texture, yield, cultivation, fertilization, etc.) and their changes via modified soil management. These include methodological investigations, such as using sieved rather than undisturbed samples to investigate the above relationships, or using physical properties as additional assessment indicators of SOM content and quality.

The results are expected as following;

• The quantitative impact of SOM on WHC will be depend on the soil textural classes and on the SOM content itself.
• SOC will have the direct and indirect impacts on WHC, whereas its direct impact is negligible but its indirect impact will be mainly affected by soil structure and aggregate composition in the higher matric potentials.
• The carbon contents will be greater in MBC and iPOC of soils amended with organic manure than mineral fertilizer or un-amended soils.
• Soil aggregates could be a good proxy for the combined physical, chemical and biological functioning of the soil. So, in forestry soils, soil aggregates will be more stable in water compared to horticulture soil.
• The highest correlation for thermal mass losses will be between 460°C and 500°C (the range of assumed decomposition of thermally stable organic matter).