Spatial variability of soil properties on the field and landscape scales in red soil areas as related to the crop yield potential
Final Report Abstract
In the light of an increasing demand for staple food, especially rice, in southeast China, investigations on the specific site potential expressed as the relation between soil and crop yield parameters gain increasingly importance. We were aiming at identifying correlative relations between soil and crop properties, and at determining the heterogeneity of hydraulic conductivity as a basis for crop yield potential assessment. Soil texture and several soil chemical parameters (total N, total C, available P, pH) as well as plant properties (crop height, biomass and grain yield) were investigated along two terraced catenas with contrasting soil textures cropped with wet rice. Additionally, dye tracer experiments were conducted on selected fields with subsequent determination of hydraulic conductivity and penetration resistance. Data were analyzed both statisfically and geo statistically on the basis of semivariograms. Statistical analysis indicated a significant influence of the relief position on the spatial distribution of soil texture, total carbon and total nitrogen content. Significant correlations were found for the catena located in a sandstone area (Catena A) between rice yield and silt as well as total nitrogen content. Corresponding relations were not detectable for paddy fields that developed from Quaternary clays (Catena B). As suggested by the nugget to sill ratio, spatial variability of soil texture, total carbon and nitrogen was mainly controlled by intrinsic factors, which might be attributed to the erosional transport of fine soil constituents, indicating the importance of the relief position and slope in soil development even in landscapes that are terraced. The crop parameters exhibited short ranges of influence and about one third of their variability was unexplained. Comparable ranges of selected crop and soil parameters, found only for catena A, are indicative of close spatial interactions between rice yield and soil features. Dye tracer experiments demonstrated equilibrium flow at Catena A (sandstone), while some bypassing along biopores was found at Catena B (Quaternary clay). Yet, the logarithmized hydraulic conductivities of the plough pan of Catena A exhibited a distinct bimodal frequency distribution, indicating that two pore systems were active. No statisfically significant differences in hydraulic conductivity, bulk density, water content or penetration resistance were found between stained, unstained and mixed areas were found. Our findings show that especially in sandstone dominated areas, a site-specific management can contribute to an environmentally safe rice production increase.
Publications
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2005. Räumliche Variabilität ausgewählter Bodeneigenschaften und Ertragseigenschaften von Reiskulturlandschaften in SE-China. Mitteilungen der Deutschen Bodenkundlichen Gesellschaft 107, 77-78
Lennartz, B., and B. Koop
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2008. Spatial variability of soil properties and rice yield along two catenas in Southeast China. Pedosphere 18, 409-420
Ruth, B., and B. Lennartz
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2009. Ecological safe management of paddy landscapes. Soil Till. Res., 102(2), 179-192
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.
