
Can Crop Temperature Guide
Center-Pivot Irrigation?By Hank Becker October 2, 2000Adding temperature sensors to a
site-specific, center-pivot irrigation system showed that it is possible to
detect water stress and manage delivery of irrigation water using that
information. Agricultural Research Servicescientists in Florence, S.C., are fine-tuning the controls for a modified
center pivot. It can independently water and fertilize nearly 700 mini-areas
within a 14-acre circle. Each area is about the size of a two-car garage. The
amount of water applied depends on the site-specific needs of plants as sensed
by infrared thermometers and other state-of-the art sensors. The modified center pivot consists of 13 30-foot-long segments with infrared
thermometers spaced about 15 feet apart. Each segment has three sets of
different-sized sprinklers. Using combinations of sprinklers, up to eight
different water-application rates can be delivered. A computer controls the
system, driven by specialized software and a database containing information
about the soil, crops and farming practices. Researchers added infrared thermometers to the system to see if water stress
was detectable, sense the canopy temperature, and prove that it was possible to
apply water to precisely address the sensed need. They also showed that the
data could be adjusted for known problems like clouds and daily, or diurnal,
cycles. During the 1999 growing season, which had less rainfall than usual, canopy
temperature measurements confirmed that corn plants encountered a wide range of
crop stress, even within a fairly small area in a field. The computer-driven
system delivered variable amounts of irrigation water, adjusted to relieve crop
stress measured as plant temperature. Soil water measurements confirmed a wide
range of soil water levels throughout the test plots. 1999 data showed the well-watered plots were up to 7 degrees C cooler than
unwatered controls on a given day. Corn yields for well-watered plots were
about 150 bushels per acre, compared with 60 bushels for the unirrigated. ARS is the chief research agency of the U.S.
Department of Agriculture. Scientific contact: E. John Sadler,
ARS Coastal Plains Soil, Water and
Plant Research Center, Florence, S.C., phone (843) 669-5203, ext. 112, fax
(843) 669-6970, mailto:[email protected].
U.S. Department of Agriculture |