DRIP IRRIGATION SCHEDULES FOR VEGETABLES By: Kerry Harrison, Extension Engineer

2 Irrigation Scheduling If the crop is using 0.25 inch of water per day, when do we need to irrigate –if the soil was at field capacity, and the crop pulled out 0.25 inch per day –then we need to irrigate every four days and put down 1.2 inches of water

SCHEDULE: Must know how much is needed (I. E inches)

Amount: Should be expressed in volume or depth - not time (i.e. 0.1 inches not 30 minutes).

ET x Pf DU Water Use = Where: ET = evapotraspiration Pf = plant factor DU = low quarter uniformity

3 Methods Used to Calculate “how much” By Volume By Time By Application Rate Assumptions: Both volume & time assume the acres per zone and flow are known App. Rate assumes that tape flowrate and wetted area are known

7 Irrigated Area and Volume With microirrigation, the whole area is not wetted –must adjust water volume

8

9

Volume and Time Example Assume you want to apply 0.1 inches Step in. X 27,000 gallons/ac-in X Acres/zone = “Target Gallons” Step 2a. Set programmable timeclock to stop operating after “Target Gallons” has gone through flow meter Step 2b. Calculate operating time for each zone by dividing “Target Gallons” by pump (zone) flowrate

Application Rate Example In Hr = 96.3 x GPM Square feet covered In Hr = 96.3 x tape flowrate Tape length x wetted width Use 100 feet of row (tape) with high and low flow tape and wetted bed widths of 3', 3.5', 4', and 4.5'.

12 Wetting Patterns with Drip Line in Raised-Beds Clay SoilLoamy SoilSandy Soil

Wetted width3'3.5'4'4.5' HF (0.45 gpm per 100') LF (0.225 gpm per 100') Application Rate for Drip Tape (Inches/hour) Notes: Tape flowrate can vary depending on pressure. Application width depends on soil type

Wetting Patterns: Are influenced by “pulsing”

Frequency: Should include scheduling management (i.e. 0.25"/day is the same as 1.75"/week but how was it applied?)

16 Irrigation Frequency In order to maximize yield, you must –understand the water requirements of the crop –understand the relationship between the plant the soil and the water –understand the design of the irrigation system

17 Time for Break

Maintenance for Drip Systems PReligious Flushing (both PVC submains and drip lines) PMaintaining adequate flows during flushing PCleaning filters (screen type filters) PHaving adequate pump capacity for filter backflush (media type filters) PPressure gauges to monitor system performance

foot Length on Zero Percent Slope

20

Maintenance for Drip Systems PReligious Flushing (both PVC submains and drip lines) PMaintaining adequate flows during flushing PCleaning filters (screen type filters) PHaving adequate pump capacity for filter backflush (media type filters) PPressure gauges to monitor system performance

22 Distribution and Filtration Pressure requirements and pumps are unique to each site –must know elevations, and acreage –must know pipe sizes –must know flowrates Need to have a qualified designer or engineer provide assistance with pump selection

23 Water Filtration Three basic types of filters –media filters (sand filters) –disk filters –screen filters

24

25 Maintenance for Drip Systems PReligious Flushing (both PVC submains and drip lines) PMaintaining adequate flows during flushing PCleaning filters (screen type filters) PHaving adequate pump capacity for filter backflush (media type filters) PPressure gauges to monitor system performance

26

27 Wrap-up Filtration is the key to long-term success with microirrigation Understanding how the whole system works is the key to being a successful irrigator –system includes the plants, the soil, and the water

28 Final Words Use many pressure gauges. –these are your indicators as to the health of the irrigation system –make sure there is enough pressure without there being too much pressure Flush the dripline –open the end while the system is running and flush the solids out