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Scientific Irrigation Scheduling Standard Protocol Measure Overview. Regional Technical Forum December, 2013. Water Balance. Precipitation: water from atmosphere to soil. Transpiration: passage of water through plant, from soil to atmosphere. Irrigation: water applied to field by grower.
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Scientific Irrigation SchedulingStandard Protocol Measure Overview Regional Technical Forum December, 2013
Water Balance Precipitation: water from atmosphere to soil Transpiration: passage of water through plant, from soil to atmosphere Irrigation: water applied to field by grower Evaporation: liquid in soil becomes vapor in atmosphere
Water Balance - Evapotranspiration Evapotranspiration = Evaporation + Transpiration • Combined transfer of water from soil to atmosphere from evaporation and transpiration. • The rate of evapotranspiration depends on: • Weather (temp, humidity, insolation, wind) • Soil type • Crop type Transpiration: passage of water through plant, from soil to atmosphere Evaporation: liquid in soil becomes vapor in atmosphere
Water Balance – Water Requirement Water Required = Evapotranspiration - Precipitation Ideally, the Irrigation water applied is exactly the amount of water required. Precipitation: water from atmosphere to soil Transpiration: passage of water through plant, from soil to atmosphere Irrigation: Water applied to field by grower Evaporation: liquid in soil becomes vapor in atmosphere
What is Scientific Irrigation Scheduling (SIS)? • Precise determination of the timing and amount of irrigation required in a field using three techniques in coordination: • Evapotranspiration and precipitation monitoring • Soil moisture monitoring • Water application monitoring
What is the SISmeasure? • Application of SIS in irrigation decision-making • Can be applied by either a consultant or by the grower • Service is provided for a single growing season • Soil moisture meters are removed at end of season • Crops may rotate from season to season • Climatic data will vary from year to year
Does not using SIS imply inefficient irrigation? Quantec Study, Phase 1. Baseline Practices • Survey of 776 farms across the PNW • Characterized irrigation practices • Compared reported water use to estimated water requirement • Findings • Practice Group II used 10% less water than Practice Group III • Practice Group I used 12% less water than Practice Group III
What is the Quantec “10%” number? Phase 2 of the Quantec examined the impact of SIS • 19 treatment group sites received SIS • 19 control group sites did not receive SIS • The control group was farms known not to use water management practices. • I.e., the control group was not a random sample of the population, it was only the least efficient irrigators. • Findings: on average, • The treatment group used the “ideal water” amount. • The control group used 10% more water than the “ideal water” amount. • Conclusion: “SIS saves 10% of the ideal water amount”