Precision Irrigation Presented by Xiaoxue Li
Precision irrigation n Definition u Also called site-specific irrigation u A tool of precision farming that involves the delivery of irrigation water in optimum amount over an entire field u New generation of innovative systems to monitor and control soil moisture deficiency and irrigation
Why PI? Internal reasons u Very few fields are uniform, the need for irrigation may differ between different zones of a particular field u Most currently used irrigation systems apply water at constant rates, therefore some areas of a field may receive too much water and other areas of a field may not receive enough water n
Why PI n Driving forces u Excessive water application could contribute to surface water runoff or leaching of nutrients and chemicals to groundwater u Precision irrigation systems would have the ability to apply water directly where it is needed, therefore saving water and preventing excessive water runoff and leaching
Systems having potential for PI n Center pivot and the similar linear-move system have higher potential u Provide an outstanding platform on which to mount sensors for real time monitoring of plant and soil conditions u Interact with a control system for optimal environmental benefits
Systems having potential for PI n Drip irrigation system also offers precision irrigation technology u However, drip irrigation represents only a small share of total irrigation u High costs limit this kind of equipment to mainly higher-value crops like fruits and vegetables
Precision irrigation scheduling n n Irrigation scheduling is the heart of precision irrigation, which simply knows where, when to irrigate and how much irrigation water to apply An effective irrigation schedule helps to maximize profit while minimizing water and energy use
Where and when to irrigate n Three ways u Measuring Soil-Water u Checkbook Method u Remote sensing
Where and when to irrigation n Measuring soil water u Quantitative methods t Neutron Scatter t Di-electric Constant Methods t Gravimetric Soil Sampling u Qualitative methods t Tensiometers t Porous Blocks
Where and when to irrigation n Checkbook method u The check-book method is an accounting approach for estimating how much soil-water remains in the effective root zone based on water inputs and outputs (like a daily balance on a bank account based on deposits and withdrawals) u Irrigation is scheduled when the soil-water content in the effective root zone is near the allowable depletion volume, otherwise irrigation should be delayed.
Where and when to irrigation n Remote sensing u Satellite image and air photo u Infrared thermometry is a more recently developed technique to determine irrigation timing based on plant canopy temperature rather than soil moisture
How much to irrigate n Enough irrigation water should be applied to replace the depleted plant available water(PAW) within the root zone and to allow for irrigation inefficiencies
PI application example n n n Location: Richland, Washingon Farmer: Thayne Wiser Farm area: 2000 acres Research area: 120 acres Irrigation Systems: self-propelled center-pivot irrigation systems
PI application example n n Research team u Washington State University u USDA-ARS u A sprinkler manufacturer Objectives u Characterize soil water spatial variations u Develop water-application prescriptions to meet the often-conflicting needs for discrete areas in the field u Engineer a variable-rate sprinkler system to deliver water in precise amounts based on prescriptions
PI application example n Procedures: u Mapping topography t Use 8 channel, L 1, C/A code DGPS to gather point data t Input point data to GIS software to generate topography map
PI application example u Scouting the Soil t Gather georeferenced soil samples on 200 foot grids t Analyze soil texture, physical and chemical properties t Create soil maps showing each soil parameter as a separate GIS layer
PI application example u Prescription Preparation t Determine management zones • 20 per field with the smallest area about one acre • 100 management zones in 120 acres t Access GIS data layers using computer models, integrate climatic data, irrigation system characterization data, and irrigation scheduling procedures based on current soilmoisture levels
PI application example Make decision about water needs of specific zones to create management map(or prescription) u Use prescription to program the sprinkler heads to deliver either more or less water in each management zone. u
PI application example u Water monitor t Place 6 passive capillary (PCAP) soil-solute samplers in research circle at a depth of 3. 5 feet to monitor soil water t Use Frequency domain reflectrometry (FDR) probes installed above PCAPs to assess soil moisture in real time t Place neutron-scattering access tubes, ceramic vacuum-extractor cups, and tippingbucket rain gauges adjacent to each PCAP to verify soil moisture measurement
PI application example Determine actual water use in each management zone and judge the effectiveness of the precision irrigation applications t Install an automated agricultural weather station to collect climatic data every 15 minutes t Connect all the monitoring devices to the dataloggers t
PI application example u Water delivery system t Divided the length of the test pivot into 30 zones, having two to four sprinkler heads apiece. Each zone had its own programmable controller t Cycled the sprinklers on and off at selected intervals over a period of time to achieve the prescribed irrigation amount in a management zone
Precision irrigation application example I n Master Control systems u Master computer collects pivot location and controller status information u The system communicates changes in application rates for each of the 30 controllers according to the controller's location on the prescription map u The control system allows the irrigator to change, at the base computer, the prescription or decision criteria for any management zone at any time during the irrigation.
PI application example I Master control system Controllers Master computer GIS base map Irrigation models Real time prescription Maps and other software Pivot location and controller status data Prescription instructions
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