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Multispectral Reflectance of Cotton Related to Plant Growth, Soil Water and Texture, and Site Elevation

^a Texas A&M Univ., Rt. 3, Box 219, Lubbock, TX 79403
^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
^e Dep. of Soil Sci., North Carolina State Univ., Raleigh, NC 27695

View larger version (18K): [in a new window]   Fig. 1. (a) Mean monthly (average of all N treatments) soil and cotton multispectrum during the growing season at the 75% evapotranspiration (ET) and (b) comparison of monthly average surface reflectance of tray dry soil reference and irrigated cotton, measured in August 1998.

View larger version (22K): [in a new window]   Fig. 2. Temporal patterns of normalized difference vegetative index (NDVI) and leaf area index (LAI) as a function of irrigation level, measured in 1998. Data were mean of N treatments because N fertilizer had no effect on NDVI and LAI. ET, evapotranspiration.

View larger version (32K): [in a new window]   Fig. 3. Temporal patterns of the (a and b) normalized difference vegetative index (NDVI) and N uptake and (c and d) cotton plant water content (PWC) and plant fresh biomass (PFB) at the 50 and 75% evapotranspiration (ET) irrigation levels, measured in 1999. Data were the mean of N treatments because N fertilizer had no effect on these variables.

View larger version (52K): [in a new window]   Fig. 4. Spatial pattern of (a and b) soil and cotton reflectance at center 661, 810, and 1650 nm related to (c and d) soil water content (SWC) and (e and f) site elevation (SE) at the 50 and 75% evapotranspiration (ET) irrigation level. Data were measured across all plots in mid-August 1999.

View larger version (17K): [in a new window]   Fig. 5. Relation between (a) reflectance in the near infrared (NIR) band (797–829 nm) and plant fresh biomass (PFB) and (b) reflectance in the midinfrared (MIR) band (1523–1752 nm) and cotton plant water content (PWC). Mean of all plots measured in 1998. ** Significant at the 0.01 level.

View larger version (15K): [in a new window]   Fig. 6. Regression of (a) red (RED) and (b) near infrared (NIR) reflectance with site elevation (SE). Reflectance data were the monthly mean measured in all plots at 50% evapotranspiration (ET) in August 1999. ** Significant at the 0.01 level.

View larger version (123K): [in a new window]   Fig. 7. Normalized difference vegetative index (NDVI) map. Spectral reflectance data were measured on (a) 90 kg N ha-1 plot and (b) 135 kg N ha-1 plot on 15 Aug. 1998. ET, evapotranspiration.

View larger version (48K): [in a new window]   Fig. 8. Cross correlation of (a and b) near infrared (NIR) reflectance and normalized difference vegetative index (NDVI) with soil water content (SWC) in 0 to 0.06 m; (c) NIR reflectance and sand; (d) red reflectance and clay; and (e, f, g, and h) NIR, NDVI, red, and midinfrared (MIR) reflectance with elevation at a lag distance of ±180 m. Soil water content and reflectance data were measured in all plots on 9 and 24 Aug. 1999, respectively. ET, evapotranspiration.