Irrigation Technology and Design. 1. Why do we Irrigate? How do we apply irrigation water? KPU Small Farm Sessions 2/13/2016

Transcription

1 Irrigation Technology and Design Stephanie Tam, P.Eng. Water Management Engineer Andrew Petersen, P. Ag Regional Resource Specialist B.C. Ministry of Agriculture 1. Why do we irrigate? 2. How much water can the soil store? 3. How much water can be applied at one time? 4. Irrigation Efficiencies 5. How much do you apply? 6. How often do we irrigate? 7. Irrigation Scheduling 1. Why do we Irrigate? How do we apply irrigation water? To grow a productive crop Sprinklers systems Trickle / Drip systems To replenish Soil Moisture Soil is our storage tank for water Soil structure Soil Structure Saturated Soil Stephanie Tam (Ministry of Agriculture) 1

2 Naturally Drains Stored Water Field Capacity Available Water Storage Capacity (AWSC) Effective Rooting Depth 50 % Table Error! No text of specified style in document..1 Effective Rooting Depth of Mature Crops Shallow 0.45 m (1.5 ft) Effective Rooting Depth Medium Shallow 0.6 m (2 ft) Medium Deep 0.9 m (3 ft) Deep 1.2 m (4 ft) 2. How much water can the soil store? Depends on soil texture and crop rooting depth. Cabbages Cauliflowers Cucumbers Beans Beets Blueberries Brussels Sprouts Cereal Clover (red) Alfalfa Asparagus Blackberries Alfalfa = 4.0 foot root depth Lettuce Onions Radishes Broccoli Carrots Celery Corn (sweet) Eggplant Kiwifruit Corn (field) Grapes Loganberries Sandy loam = 1.5 inch water / foot Turnips Grass Peas Potatoes Spinach Peppers Squash Saskatoons Raspberries Sugar beets Tree Fruits (12 x 18 ) Total AWSC = 4.0 x 1.5 Strawberries Tomatoes Tree Fruits (3 x 10 ) Tree Fruits (6 x 12 ) = 6.0 inch Stephanie Tam (Ministry of Agriculture) 2

3 Grass Crop If Grass is grown instead of alfalfa: Grass = 1.5 foot root depth Compare Crops on Sandy Loam Soil For a ALFALFA crop: Sandy loam = 1.5 inch water / foot Total AWSC = 6.0 inch Total AWSC = 1.5 x 1.5 = 2.2 inch For a GRASS crop: Total AWSC = 2.2 inch BUT! Not all the water in the soil is readily available to the crop. Availability Coefficient, (AC) 3. How much water can be applied at one time? Maximum Soil Water Deficit (MSWD) MSWD = AWSC x AC Maximum percentage of the total AWSC that the crop can remove before irrigation should occur again. Alfalfa and Grass 50 % MSWD (Alfalfa) = 6.0 x 0.50 = 3.0 inch What if it was a Grass Crop? Peak Evapotranspiration Maximum Soil Water Deficit for a grass crop is: MSWD (Grass) = 2.25 x 0.50 = 1.1 inch MSWD (Alfalfa) = 6.0 x 0.50 Vancouver = 0.18 in/day Vernon = 0.22 in/day Kelowna = 0.24 in/day = 3.0 inch Stephanie Tam (Ministry of Agriculture) 3

4 Maximum Irrigation Interval Max Irrigation Interval = MSWD / ET Vernon Alfalfa = 14 days Vernon Grass = 5 days Vancouver Alfalfa = 17 days Vancouver Grass = 6 days Irrigation Scheduling 1. Efficiency: Select the most efficient type of irrigation system possible 2. Uniformity: Design the system to obtain the best uniformity 3. Scheduling: Schedule irrigation timing according to soil moisture or climate data Certified Irrigation Designer Certification in: Ag sprinkler Ag Drip Being developed: Agriculture Technician Irrigation scheduling 4. Irrigation Efficiencies Application Efficiency is an indication of the percentage of water applied by an irrigation system that is actually available to the crop. Affected by: Wind, operating pressure, sprinkler trajectory, time of day and hot or cool weather Design, operation, and maintenance System type Micro Sprinkler Stephanie Tam (Ministry of Agriculture) 4

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6 Water Management Goals Sprinkler Irrigate to fill the root zone Schedule to irrigate when soil moisture = 50% field capacity Trickle (Drip) Maintain soil moisture content at optimum level Reduce plant moisture stress Apply frequent but low flow of water 5. How much do you apply? On a sandy loam soil the maximum soil water deficit (MSWD) Alfalfa = 3.0 inch Grass = 1.1 inch Infiltration Rate, (AR) Maximum Application Rates Maximum infiltration rate of the soil Different for each soil type If it is exceeded: Ponding, Runoff, and Erosion Potential environmental concerns Application Rate, (AR) AR = 96.3 x Q SS x LS AR = application rate (in/hr) Q = nozzle flow rate (gpm) SS = sprinkler spacing (ft) LS = lateral spacing (ft) Example - Wheel line AR Standard Wheel line with 40 foot sections 60 ft move and 9/64 50 psi Nozzle Flow Rate (Usgpm) PSI 9/64 5/32 11/64 3/ AR = 96.3 x Q SS x LS AR = 96.3 x x 60 = in/hr Stephanie Tam (Ministry of Agriculture) 6

7 6. How often do we Irrigate? Depends on EVAPOTRANSPIRATION and amount applied by the irrigation system Wind Solar Radiation Gross Water Applied (GWA) Amount of water applied to the soil. Relative Humidity Transpiration GWA = AR x Set Time (hr) Evaporation Temperature GWA = x 23.5 GWA = 3.87 inch Effective Roots Net Water Applied (NWA) Amount of water that enters the soil. NWA = GWA x AE NWA = 3.87 x 0.72 Actual Irrigation Interval Net Amount Applied divided by the ET (Vancouver) Irr Interval Irr Interval = NWA / ET = 2.8 in / 0.18 in/day NWA = 2.8 inch Irr Interval = 15 days Trickle Water Requirement Plant Water Requirement For point source trickle systems water requirement is calculated per plant Water / Plant / Day For both designs need to calculate plant water requirement. G/P/D= x ET x S x A x K For linear tape systems water requirement is calculated per row Water / Row / Day ET - Peak evapotranspiration S - Soil water storage factor A - Area per plant K - Crop coefficient factor Stephanie Tam (Ministry of Agriculture) 7

8 Soil Water Storage Factor, S Crop Coefficient Factor, K Based on rooting depth of crop and evapotranspiration. Field area utilized by the plant root area. Effective Soil Water Storage Factor MSWD Peak ET (in/day) S Factor inches inches inches Crop Crop Coefficient Factor (K) Crop Coefficient Approximate Spacing Apples 0.9 Grapes 0.7 Apricots 0.8 Blueberries 0.8 Cherries 0.9 Blackberries 0.6 Peaches 0.8 Kiwi Fruit 1 Pears 0.8 Logan Berries 0.6 Plums 0.8 Raspberries 0.7 Tree Fruits High Density 1 Strawberries 0.75 Tomatoes 0.9 Vegetables 0.75 Drip Irrigation Design Blueberry field in Abbotsford Spacing 2.5 x 10 Loam Soil (MSWD = 2.1) Peak ET of 0.16 in/day Plant Water Requirement Blueberries in Abbotsford. G/P/D = x ET x S x A x K = x 0.16 x 0.75 x 25 x 0.8 = 1.5 USgpd (5.7 lpd) Plant Water Requirement (Abbotsford) Trickle System Design Capacity Blueberries Raspberries Strawberries = 1.50 USgpd (5.7 lpd) = 1.00 USgpd (3.8 lpd) = 0.25 USgpd (1 lpd) TC = G/P/D x L E x Eu GPD - gallons per plant per day L - leaching factor E - application efficiency Eu - emission uniformity Stephanie Tam (Ministry of Agriculture) 8

9 Trickle System Design Capacity (Abbotsford) Daily System Operating Time (Abbotsford) Blueberries Raspberries Strawberries = 1.80 Usgpd (6.8 lpd) = 1.27 Usgpd (4.8 lpd) = 0.31 Usgpd (1.2 lpd) Emitters supplying 0.5 USgph per plant (1.9 lph) Blueberries = 3.6 hours Raspberries = 2.5 hours Strawberries = 0.6 hours 7. Irrigation Scheduling Irrigation Scheduling Irrigate according to crop requirement not to a fixed date. Irrigate only when necessary Apply only what the soil can hold Requires knowledge on climate, soil and irrigation system Stephanie Tam (Ministry of Agriculture) 9

10 Irrigation System Assessment Peak flow rate Annual water use System assessment/conversion Existing irrigation system min. 15% efficiency improvement Certified Irrigation Designer Irrigation Management Irrigation scheduling equipment Weather station Soil moisture sensors Valves, controllers Provide data to Pacific Field Corn Association Free climate data and calculators Over 100 climate stations in BC Stephanie Tam (Ministry of Agriculture) 10