Remote Sensing in Precision Irrigation Zhiming Yang Remote

Remote Sensing in Precision Irrigation Zhiming Yang

Remote Sensing in Precision Irrigation n Image-based remote sensing u Satellite u Aircraft Radar u Synthetic Aperture Radar (SAR) Field-based remote sensing u Infrared Thermometer(IRT)

Image-based remote sensing n Satellite u Thermal scanner (Thermal band) t Landsat TM, NOAA u Water stress detection and evaluation of irrigation system performance u Evaportranspiration (ET)

Image-based remote sensing Evapotranspiration in Florida, Feb. 29, 1996. Prepared from GOES satellite imagery ( NASA IITA Project. 9/96 )

Image-based remote sensing n Aircraft u Thermal scanner u Water stress detection u E. g. Aircraft-mounted sensors detect water stress of cotton in central California

Image-based remote sensing E. g. A thermal image of a cotton canopy from a helicopter

Image-based remote sensing Limitations u Satellite Thermal band temporal resolution Landsat TM 60 m 16 days NOAA 1100 m 0. 5 days u Aircraft t High cost t Difficult for geometric correction n

SAR Advantage t SAR sensors are sensitive to soil moisture and can be used to directly measure soil moisture u Disadvantage t Data requires extensive use of processing to remove surface induced noise such as soil surface roughness, vegetation. u

Field-based remote sensing n n n Advantages u High resolution u Being able to control monitoring conditions u Easy to quantify measurement results Disadvantage u Difficult for large area Infrared thermometer u Easy and convenient to use

Infrared thermometer

Precision Irrigation by IRT n Where and when to irrigate n Temperature and time threshold u Crop water stress index (CWSI) How much to irrigate u Evaportranspiration u Crop water requirement u

Infrared thermometer n

Temperature and time threshold n n Temperature threshold(To) u A biologically determined optimum temperature for each crop Time threshold (TT) u A specific quantity of time when canopy temperature is above the To

Temperature and time threshold Irrigate where and when crop is warmer than temperature threshold and it lasts longer than time threshold in a day n Temperature threshold – crop-specific Cotton and corn 82 0 F, Soybean 84 0 F n Time threshold - location-specific(eg. Cotton) n Locations Threshold time(hour) Lubbock, TX Shafter, CA Missipipi State, MS 4. 6 6. 8 6. 9

Crop water stress index (CWSI) n Many methods to calculate CWSI n CWSI = TC = canopy temperature TCi = Sensed for irrigation TCmin = non-watered stressed and calculate from solar radiation and humidity readings or measured in a well-watered plot TCmax = “completely” water stressed and calculate from air temperature and solar radiation

CWSI n n n Irrigate for sensitive crops where and when CWSI is between 0. 2 and 0. 5 Irrigate for drought-tolerant crops where and when CWSI is between 0. 5 and 0. 7 E. g. , corn could go as high as 0. 4 on the crop water stress index and still produce a harvest, whereas cotton has a much lower stress threshold

How much to irrigate n n Evaportranspiration(ET) u Integrate IRT data, weather station data and ET model to calculate ET Crop water requirements u Software t IWR(Silsoe College) t KANSCHED (K-state Research and Extension) t IRT-Etc(Center for irrigation technology)

PI Example II n n n Location: Florence, SC Irrigation Systems: self-propelled center-pivot irrigation systems Research team: Carl Ro Camp, Eo John Sadler and etc, Coastal Plains Soil, Water, and Plant Research Center, USDA-ARS

PI Example II n

PI Example II n Objective To manage water and chemical applications to small areas within the total irrigation system area based on stored data, real- time plant and soil measurements, or a combination of the two on Coastal Plain soils

PI Example II n Methods u Modify two commercial center pivot irrigation systems with computer-aided management u The system is controlled by a computer using specialized software and soil, crop, and cultural information stored in a database to control all water and nutrient applications

PI Example II Infrared thermometers are mounted on top of the vertical masts at right end of horizontal tubes to measure crop water stress. The modified application system has been used to apply water and nitrogen to a field experiment with fixed, regular plot boundaries u Current work includes improvements to make the system more reliable and to accommodate irregular-shaped areas of variation. u

Limitations n n IRT method is applicable only to mature plants with a well-developed canopy. It is not applicable to calculations of bare soil evaporation Misleading u Sharp climatic changes may cause low canopy temperatures even when soil water is limited; Alternatively, under such conditions, high canopy temperatures may be observed when soil water is not limiting u Some other stresses such as pest infestation can also rising of canopy temperature

PI Example II n

Any Questions ?