ARS | Publication request: COMBINING REMOTELY-SENSED CROP COEFFICIENTS WITH THE FAO-56 IRRIGATION SCHEDULING PROCEDURES.

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: November 13, 2002
Publication Date: N/A

Technical Abstract: An experiment was conducted at the UA Maricopa Agricultural Center to determine if the normalized difference vegetation index (NDVI) could provide crop coefficients for scheduling cotton irrigations. Treatments included two scheduling approaches based on Food and Agricultural Organization Paper No. 56 (FAO-56). The first calculated daily evapotranspiration (ET) from a locally-derived, basal crop coefficient (Kcb) curve developed using FAO-56 guidelines. The second used Kcbs based on ground-measured NDVI and a previously defined relationship between NDVI and cotton water use. Reference ET for both was calculated per FAO-56 using local weather data. Additional variables (3 plant densities, 2 N levels) created conditions that altered crop water use yet are not commonly nor easily accounted for in typcial FAO-56 use. Supporting measurements included overflights with a precision 3 CCD camera and thermal scanner plus observations of soil water, canopy temperature, stem flow, crop growth and yield. Results revealed the potential for NDVI to provide near-real time feedback for adjusting Kcb to variations in cultural and edaphic conditions and may result in more efficient irrigations.