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Irrigation Scheduling. Phil Tacker Extension Engineer University of Arkansas. Irrigation Scheduling. Determining when to irrigate and sometimes how much irrigation water to apply. We irrigate most of our crops in the Arkansas Delta. Rice: 1.5 million acres - all irrigated
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IrrigationScheduling Phil Tacker Extension Engineer University of Arkansas
Irrigation Scheduling Determining when to irrigate and sometimes how much irrigation water to apply
We irrigate most of our crops in the Arkansas Delta Rice: 1.5 million acres - all irrigated Corn: 350,000 acres – 80% irrigated Cotton: 1 million acres - 75% irrigated Soybeans: 3 million acres - 62% irrigated Milo: 250,000 acres – 50% irrigated 4.5 million irrigated acres – 74% of total acres
Going by the calendar, crop appearance, soil cracks etc. usually not good enough.
Indicator Arm Soil Water Is Full Irrigate
Computerized Irrigation Scheduler Distributed through internet: (www.aragriculture.org/computer/schedule) and is available on CD
Keeps track of the Soil Water (Moisture) Deficit Room for more water. Soil holds all the water it can.
Arkansas Irrigation Scheduler Designed for minimal input data, don’t need an expensive automatic weather station. Measure Rain in Field
Scheduler Used in Crop Verification Programs Double-Cropped 4 Furrow Irrigations Total Rainfall: 10.39” Irr. Terminated: 9/17 R1 R6 Target Deficit = 1.75”
Irrigation Methods • Flood • Furrow • Pivot • Border
Irrigation Scheduler Assumptions • Good surface drainage – minimum standing water 24 hrs after rain and/or irrigation • No surface runoff until deficit is depleted • crusting • application rate • effective rainfall • Crop uses water at rate of non-stressed plant • The soil moisture deficit returns to zero when a field is surface irrigated
Scheduler updated periodically Investigating water use functions to see if they need updating for southern conditions to see if corn/cotton need to consider relative maturity of cultivar (like soybeans) Changes currently being considered adjustments for early/late cotton direct input of reference (potential) ET for users with access to better weather data drip irrigation scheduler
Program Use • Primarily in Arkansas • Some program users in: MS, TN, LA, MO, KY • Adaptable to other areas
Sometimes not able to keep on schedule Insufficient water Insufficient time/labor Insufficient commitment
Summary In order to manage irrigation so it gives the best results, it is important to use an irrigation scheduling method that you feel is practical and that helps you irrigate timely enough to satisfy the crop’s water needs during the season.
Acknowledgments Arkansas State Cotton Support Committee Arkansas Soil & Water Conservation Commission