Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2005
Publication Date: 5/1/2005
Citation: Iqbal, J., Read, J.J., Thomasson, A., Jenkins, J.N. 2005. Relationships between soil-landscape and dryland cotton lint yield. Soil Science Society of America Journal. 69:872-882. Interpretive Summary: Topography and field elevation are important features that shape the spatial variability of soil physical and chemical characteristics, and therefore crop production, especially under dryland conditions. Studies were conducted in 2001 in a 104-acre field with a rolling topography in order to (1) determine the spatial variability of soil properties and their effects on yield in cotton (Gossypium hirsutum L.), and (2) use a Geographic Information System (GIS) to derive topographic and hydrologic landscape attributes from high resolution elevation data. The dominant soils of the field are classified as Vaiden soil series, which consists of very deep, somewhat poorly drained, very slowly permeable soils that formed in clayey sediments overlying chalk or calcareous clays. Topographic land features included elevation (measured with an accuracy of 1-2 cm), and GIS-derived values for slope, curvature, aspect, wetness index, flow direction, flow length, flow accumulation, and sediment transport index. Soil properties and lint yield were determined from 24 sites based on an NDVI map of the previous year's crop, soybean (Glycine max L.). High elevation areas generally yielded lower (r = -0.50) and experienced water stress earlier in the season, as compared to low-lying areas. About 82% of the observed variability in lint yield was explained by a combination of important soil physical properties and derived topographic variables. Results indicate site-specific yield differences were influenced by residence time of water, sediments, and soil nutrients in the landscape.
Technical Abstract: Topographical land features greatly influence spatial variability of soils and in turn affects cotton (Gossypium hirsutum L.) yield, especially under dryland conditions. Objectives of this study are to 1) characterize spatial variability of soil physical properties in a complex, non-irrigated landscape, 2) use Geographic Information System (GIS) to derive topographic and hydrologic landscape attributes from a high-resolution elevation map, and 3) determine relationships among various soil, crop and topographic variables. The dominant soil series in the 42-ha field are Vaiden (very-fine, smectitic, thermic Aquic Dystruderts), which consists of deep, somewhat poorly drained clayey soils that formed over chalk or calcareous clays. Landscape features included elevation (1-2 cm accuracy) and derived values for slope, curvature, aspect, wetness index, flow direction, flow length, flow accumulation, and sediment transport index. Surface (1-8 cm depth) soil properties and lint yield were determined from 24 sites, selected on the basis of a soybean (Glycine max L.) NDVI map from July the previous year. Step-wise linear regression across sites indicated variation in lint yield was explained by soil properties (65 %), and topographic variables (40 %); as well as their combined effects (82 %). Elevation, percent sand, and volumetric water content at 0.001 MPa explained most of the yield variation. Yield tended to decrease as elevation increased(r = -0.50). Inclusion of derived topographic variables with soil physical and chemical properties helped in explaining spatial variability of lint yield in a complex landscape.