Ecological safe management of terraced rice paddy landscapes

• Published in: Soil & tillage research 2009-03, Vol.102 (2), p.179-192
• Main Authors: Lennartz, B., Horn, R., Duttmann, R., Gerke, H.H., Tippkötter, R., Eickhorst, T., Janssen, I., Janssen, M., Rüth, B., Sander, T., Shi, X., Sumfleth, K., Taubner, H., Zhang, B.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; crop yield; Fundamental and applied biological sciences. Psychology; kriging; landscape ecology; landscapes; Microhabitat; Oryza sativa; Paddy soil; paddy soils; Physical properties; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Preferential flow; puddling; remote sensing; Rice production; Scale transition; Soil hydraulic properties; soil management; soil physical properties; Soil regionalization; Soil science; soil water regimes; spatial distribution; terrace soils; terraces; Water and solute dynamics
• ISSN: 0167-1987; 1879-3444
• DOI: 10.1016/j.still.2008.07.010

Ecological safe management of rice paddy landscapes is in focus of a joint research project comprising five German working groups and Chinese partners. The project is aiming at characterizing the scale-depending structures and processes of agricultural landscape of terraced paddy fields in southeast China. The specific objectives were the enlightenment of the linkage between remote sensible information and the spatial distribution of soil features, as well as soil structural processes and their relation to vertical and lateral water losses and solute leaching. The experimental watershed is located in southeast China. The soils which either developed from quaternary clay or red sandstone exhibit a (man-made) layered structure with three hydraulic-functional horizons: puddled layer, plough pan and the (water unsaturated) subsoil. The analysis of soil texture and selected chemical parameters on the catenary and catchment scale confirmed that even in old terraced and thoroughly modified landscapes, the original structures (unaffected by man) of catenary soil property distributions persist. Thus, the application of co-regionalization techniques incorporating topographical attributes as explaining variables was found to be suitable to characterize soil property distributions on both the catenary and the catchment scale. On-site field scale investigations revealed that paddy soils exhibit a dynamic soil–water system which is driven by the mechanical seed bed preparation (puddling) on the one hand and drying and wetting cycles including ponded/flooded periods on the other. It was found that the hydraulic properties depend mainly on the duration of cultivation as a rice paddy. In contrast to earlier studies, we found that a further decrease in the saturated hydraulic conductivity of the plough pan may still occur after 20 years. Even in older rice paddies, however, water losses may be significant mainly because of ineffective functioning of the surrounding bunds. Pedon and aggregate investigations demonstrated the pronounced dual porosity nature of the paddy soils with a macropore network consisting of cracks and biopores penetrating both the plough pan and the bunds. The shrinkage potential of the puddle layer was higher in older paddy fields than in younger ones while it was vice versa for soil from the plough pan. Swelling and shrinkage affected also the living conditions for soil microorganisms especially after drainage when the habitable pore space was signifi