Multispectral Reflectance of Cotton Related to Plant Growth, Soil Water and Texture, and Site Elevation
- Hong Liae,
- Robert J. Lascano *b,
- Edward M. Barnesc,
- Jill Bookerb,
- L. Ted Wilsond,
- Kevin F. Bronsona and
- Eduardo Segarrae
- a Texas A&M Univ., Rt. 3, Box 219, Lubbock, TX 79403
e Dep. of Soil Sci., North Carolina State Univ., Raleigh, NC 27695
b Texas A&M Univ., USDA-ARS, 3810 4th Street, Lubbock, TX 79415
c USDA-ARS, U.S. Water Conserv. Lab., 4331 E. Broadway, Phoenix, AZ
d Texas A&M Univ., 1509 Aggie Drive, Beaumont, TX 77713
Radiometric data can be useful to determine the impact of field heterogeneity, irrigation, and fertilization on plant water and N use. A 2-yr (1998–1999) study was conducted on the South Texas High Plains to investigate cotton (Gossypium hirsutum L.) spectral and agronomic responses to irrigation and N fertilization and to determine the simple and cross correlation among cotton reflectance, plant growth, N uptake, lint yield, site elevation (SE), and soil water and texture. The treatments were irrigation at 50 and 75% of calculated cotton evapotranspiration (ET) and N rates of 0, 90, and 135 kg ha−1 arranged in an incomplete block of size-2 design. Plant and soil spectral properties were investigated within a wavelength of 447 to 1752 nm. Near-infrared (NIR) reflectance was positively correlated with plant biomass and N uptake. Reflectance in the red and midinfrared band increased with SE. The mixed-model analysis showed that cotton NIR reflectance, normalized difference vegetative index (NDVI), soil water, N uptake, and lint yield were significantly affected by irrigation (P < 0.0012). The N treatment had no effect on spectral parameters, and interaction between irrigation and N fertilizer was significant on NIR reflectance (P < 0.0027). All spectral and agronomic parameters measured were associated with SE. The red and NIR reflectance and NDVI were cross-correlated with soil water, sand, clay, and SE across a distance of 60 to 80 m. Characterization of plant and soil reflectance and their spatial structure can be the basis for variable N application on heterogeneous fields to increase N use efficiency.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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