AGRICULTURAL IRRIGATION WORKSHOP. Presented by: B.C. Ministry of Agriculture Sustainable Agriculture Management Branch

Transcription

1 AGRICULTURAL IRRIGATION WORKSHOP Presented by: B.C. Ministry of Agriculture Sustainable Agriculture Management Branch Year 2012

2 Agricultural Irrigation Workshop This workshop is intended to help environmental agencies and local government staffs understand agricultural irrigation. How much do you know about agricultural irrigation? Can you answer these questions? 1. Why does Abbotsford supply 4 gallons per minute per acre to each farm? 2. How does soil affect irrigation system operation? 3. Why do farmers often need to irrigate in the rain? 4. Why do farmers irrigate 24 hours a day? 5. How can agricultural irrigation be made more efficient? 6. How is an annual water allocation determined for a farm? Topics covered include: Linking crop, climate data and soils with irrigation design and operation. Review of irrigation system types, their operation and efficiencies. Irrigation scheduling techniques Presented by: Sustainable Agriculture Management Branch Ministry of Agriculture

3 List of Handouts 1. Selecting an Irrigation System (from B.C. Irrigation Management Guide) 2. Preparing a Farm Irrigation Plan (Factsheet ) 3. Soil Water Storage Capacity and Available Soil Moisture (Factsheet ) 4. Calculation of an Irrigation Water Supply Flow Rate (old factsheet) 5. Crop Coefficients for Use in Irrigation Scheduling (Factsheet ) 6. Irrigation Tips to Conserve Water on the Farm (Factsheet ) 7. Agricultural Irrigation Scheduling Calculator (Factsheet ) List of Websites Sustainable Agriculture Management Branch publication website for a full list of publications and factsheets: Agricultural Irrigation Scheduling Calculator at the Irrigation Industry Association of B.C. (IIABC): Evapotranspiration (ET) Calculator at Farmwest:

4 Selecting an Irrigation System Proper selection of an irrigation system includes taking into consideration system type, design, operation and maintenance. The type of irrigation system most suitable for a particular site depends on crop characteristics, climate, soil and site conditions. A brief description of each system follows. Irrigation Systems at a Glance Trickle/Drip Systems Trickle/drip systems are the most efficient method of irrigation if managed properly, but they are not suitable for all cropping systems. Trickle/drip systems are most applicable to horticultural crops, such as tree fruits, berries, grapes, vegetable and other plants grown in rows. Trickle systems can be designed to match almost any soil condition providing that plant root volume and lateral movement of water in the soil is considered. Water of poor quality will require filtration systems to ensure that the system is able to operate properly. In this Guide, trickle refers to frequent, low-pressure application of water to crops, including tape, drip and spray emitter systems. Subirrigation systems use subsurface drain lines to provide irrigation water to the crop by raising the water table in the field. This requires closer drain tile spacings than what is used for conventional drainage. These systems can allow an efficient use of water if managed properly. The drainage system is controlled and closed, and nutrients that may have leached into the drain water are recycled to the crop. Controlled Drainage and Subirrigation Sprinkler Systems There are many types of sprinkler systems. Sprinkler systems can be efficient providing that the systems are designed with good uniformity in mind. Poor uniformity or poor management will have high water and nutrient losses due to deep percolation and overland flow. Handmove and wheelmove systems generally have standard sprinkler spacings as aluminum pipes of standard lengths are usually used. Overhead or Undertree solid set systems can have a variety of sprinkler spacings as the sprinkler layout must match the crop spacings. Lateral lines are usually buried PVC or polyethylene pipe. Microsprinkler systems tend to be more efficient than sprinkler systems as the sprinkler heads operate at lower pressure reducing misting and are spaced much closer together which may improve uniformity. Source: B.C. Irrigation Management Guide Page 1

5 Large Volume Sprinkler or Gun Systems Guns systems operate at much higher flows and pressures than regular sprinkler systems. Increased wind drift results in higher evaporation losses and lower operating efficiencies than the smaller sprinkler systems. Stationary guns generally have a very high application rate. The set times for these systems should be very short to avoid deep percolation or runoff. The short set time makes these systems very difficult to manage properly. Travelling guns overcome the problem of the short set time for stationary guns by moving the gun over a large area during one set. They are still susceptible to wind drift and evaporation losses because of the high operating pressures required by the gun. Other Systems Centre pivot systems can have higher efficiencies than sprinkler systems if low volume spray heads are used. The system travels around the field which makes it easier to match the water application to the crop and soil conditions. These systems are also automated which reduces the labour component and adds flexibility in management. Flood irrigation systems in British Columbia are usually not designed in a fashion that includes recycling of the tail water that is leaving the end of the field. Since fields are also not laser levelled, most flood systems in British Columbia are not very efficient. Figure 6.1 shows some examples of irrigation systems. Factors Affecting Selection of Irrigation Systems The following factors should be considered when selecting an irrigation system: field size and shape topography irrigation efficiency cost labour management maintenance crop type pressure requirement water quality other uses: frost protection crop cooling fertigation Field Size and Topography The field size and configuration often dictates what type of system is suitable for that location. Centre pivot systems require large symmetrical parcels of land to operate effectively. Wheel lines operate best on rectangular-shaped properties that are at least 20 acres. Travelling guns are more flexible and can adjust to different field sizes and shapes. Source: B.C. Irrigation Management Guide Page 2

6 Centre Pivot Overhead Solid Set Stationary Gun Drip Wheelmove Micro-Sprinkler Handmove Travelling Gun Travelling Gun Figure 1 Examples of Irrigation Systems Source: B.C. Irrigation Management Guide Page 3

7 Irrigation System Application Efficiency Table 6.1 provides a range of irrigation application efficiencies. Application efficiency is an indication of the percentage of water applied by the irrigation system that is actually available to the crop. Lower efficiencies mean more water is lost during the application process to evaporation, wind drift or runoff and is not available to the crop. Efficiencies of irrigation systems can vary due to wind, operating pressure, sprinkler trajectory, time of day and hot or cool weather. The efficiency can also be affected by the design, operation and maintenance of the irrigation system. Application efficiency can be assessed by conducting an irrigation audit to determine the percentage of water that is actually available to the crop. If the irrigation system efficiency has not been determined by an irrigation system audit, use the efficiencies shown in Table 6.1 when completing worksheets in this Guide. Using the lower or upper limit of an efficiency range may under- or over-estimate water use. Some general rules of thumb for determining application efficiencies are: A lower value should be used if the farm is in a hot climate region or very windy area. A higher value can be used if the farm is in a cool climate area and irrigation is applied during periods of low wind or irrigation is only applied at night. Table 1 Application Efficiencies and Costs of Irrigation Systems Irrigation System Type Application Efficiency [%] Range Typical Trickle Trickle Estimated Cost per Acre [2003$/acre] Labour Cost [hr/set/acre] 0.05 Drip Subsurface ,400 2, Microjet Sprinklers Handmove Wheelmove Undertree Solid Set Overhead Solid Set ,200 2, Micro-sprinklers Guns Travelling , Stationary Centre Pivot Sprinklers Spray Heads , Drop Tubes Flood Source: B.C. Irrigation Management Guide Page 4

8 Labour Automated systems such as trickle/drip, centre pivots and solid set sprinklers have low labour requirements compared to other systems. These systems do not have to be manually moved and irrigation scheduling changes can be done by adjusting the system control. Irrigation systems, such as wheelmoves, handmoves and guns require daily labour to move the system from one set to the next. The labour cost may also be increased if travel distance to the field is significant. Cost The capital cost of an irrigation system is often a major consideration when deciding on what type of system to purchase. However carefully considering annual maintenance, operating costs, labour, improved system management and water savings may make the more expensive systems more attractive in the long run. Irrigation Equipment Costs 2003 Management and Maintenance System management and maintenance will vary with different system types, field topography, operating pressures, type of material (PVC, steel etc) and installation. All systems require regular maintenance, but automated systems are easier to manage. Crop Type Crop type will often dictate what type of system will work best in a given situation. For example, a solid set system in a corn field is impractical for harvesting or cultivation. Also, a system that is low to the ground will not be able to spread water very far when the crop is taller than the irrigation nozzles. Trickle systems are best suited for horticultural and other row crops where water can be applied to a localized root zone. Pressure Requirement Irrigation guns have a high pressure requirement to obtain proper stream dispersal while centre pivot and trickle systems can operate with very low pressure. The pressure requirement is also determined by elevation and pipe friction losses due to system flow rate. If the proper pressure requirement for a system cannot be delivered, a different system should be considered or adjustments to the design changed. Water Quality Water of poor quality can sometimes cause staining on crops. This is undesirable for crops that are sold for fresh market or graded on appearance. Irrigation systems that do not spread water on the fruit, such as a trickle system, would be desirable in these cases. Water quality also affects the type of screening or filtration equipment that may be required. Water with high sediment content will wear nozzles, pipes, pump impellors and impellor shafts more quickly, increasing maintenance costs dramatically. Source: B.C. Irrigation Management Guide Page 5

9 Irrigation Order No Agdex: 753 February 1985 PREPARING A FARM IRRIGATION PLAN The design and installation of a good irrigation system requires information on soils, crops, climate, water supply and topographical field data. REASONS FOR AN IRRIGATION PLAN A project plan enables the designer to lay out the irrigation system in the most cost effective way. The plan is used to generate a material list and to evaluate the anticipated project costs. The plan provides step by step information on system installation. Information on crop spacing, sprinklers, pumping requirements, pipeline sizes and lengths should be included on the plan. Pertinent obstructions such as roads, trees, gas, oil, water, telephone or transmission lines must also be indicated. Specification, design standards and work schedules as set out on a plan form the basis of any contractual agreements between the installation contractor and the farmer. The plan provides a record for future reference. It can be used for overall farm planning and identifies limits of expansion potential. The irrigation plan should be passed on to subsequent landowners. ESSENTIAL FEATURES OF A PLAN Topographic Data The field shape must be accurately drawn showing pertinent obstructions, features and elevation details. Water Source Capacity The water supply must be clearly indicated showing location and available capacity. Depending on the water source, a well log or water licence must accompany the irrigation plan. Irrigation reservoirs also require Water Management Branch licensing. Soil and Crop Characteristics Soil and crop limitations must be accounted for to reduce runoff and deep percolation by mismanagement of the irrigation system. Design Parameters Soil water holding capacity, maximum application rate and climatic data must be used to select the correct irrigation system design. Design Data The nozzle selected, operating pressure, discharge rate and sprinkler spacing must all be shown on the plan. The irrigation interval, set time, application rate and net amount applied must also be calculated. Page 1 of 4

10 SPRINKLER IRRIGATION DESIGN INFORMATION SOILS REPORT Name Crop Root Depth (in) PIT A PIT B PIT C Soil Depth (in) Texture AWSC (in/ft) Texture AWSC (in/ft) Texture AWSC in/ft) 0 12 in in in in Total AWSC (in) Max Applic. Rate (A.R.) (in/hr) DESIGN PARAMETERS Crop.. Root depth. ft Soil type.... Total available water storage capacity (AWSC).. in Usable amount of water ( % AWSC).... in Maximum application rate (AR)... in/hr Evapotranspiration rate (ET). in/day Water source (gpm available)... gpm DESIGN DATA Interval.. days Set time. hours Gross applied per irrigation.. in Net % efficiency. in Application rate. in/hr Spacing.. ' x ' Nozzle x Pressure at the nozzle psi Gallons per minute per nozzle.. gpm MAINLINE FRICTION LOSS CALCULATION x x ' - gpm - x = psi x x ' - gpm - x = psi x x ' - gpm - x = psi x x ' - gpm - x = psi x x ' - gpm - x = psi x x ' - gpm - x = psi x x ' - gpm - x = psi x x ' - gpm - x = psi Total Friction Loss in Mainline psi = ft TOTAL HEAD REQUIRED Pressure required at start of psi ft Total friction loss in mainline... ft Elevation ft Suction lift or pump setting in well ft Miscellaneous losses.. ft Total Head Required ft PUMP SPECIFICATIONS Total head required. ft Total gpm required. gpm Minimum pump efficiency % Model (to be filled in by dealer) HORSEPOWER REQUIRED H.P. = ft x gpm = hp 3960 x % Page 2 of 4

11 Mainline and Lateral Layout All mainline and lateral locations and sizes should be shown. Calculations of pipeline lengths and corresponding friction losses should be indicated on the plan. Pump Specifications The pump horsepower requirements must be calculated from the total dynamic head and maximum system flow rate. The total dynamic head calculations must include system operating pressure, elevation differences and all friction losses. WHERE TO OBTAIN A PLAN A farm irrigation plan can be obtained from irrigation engineering consultants as well as reputable irrigation equipment dealers. An irrigation equipment dealers list is available from the Ministry of Agriculture and Food, Resource Management Branch. The features of a farm irrigation plan are summarized in the sample Sprinkler Irrigation Design Information sheets attached. A sample of an irrigation design plan is also included. For further information on preparing a farm irrigation plan, see the BC Sprinkler Irrigation Manual. This publication is available from BC Ministry of Agriculture and Food. SAMPLE FARM MAP Page 3 of 4

12 FOR FURTHER INFORMATION CONTACT Ted Van der Gulik, Senior Engineer Phone: (604) RESOURCE MANAGEMENT BRANCH Ministry of Agriculture and Food 1767 Angus Campbell Road Abbotsford, BC CANADA V3G 2M3 Page 4 of 4

13 Water Conservation Order No Revised February 2002 Agdex: 550 SOIL WATER STORAGE CAPACITY AND AVAILABLE SOIL MOISTURE SOIL WATER STORAGE For irrigation the soil water storage (SWS) capacity is defined as the total amount of water that is stored in the soil within the plant s root zone. The soil texture and the crop rooting depth determine this. A deeper rooting depth means there is a larger volume of water stored in the soil and therefore a larger reservoir of water for the crop to draw upon between irrigations. Knowing the soil water storage capacity allows the irrigator to determine how much water to apply at one time and how long to wait between each irrigation. For example, the amount of water applied at one time on a sandy soil, which has a low soil water storage capacity, would be less than for a loam soil, which has a higher soil water storage capacity. This is assuming the crop s rooting depth is the same for both soils. Applying more water to the soil than can be stored results in a loss of water to deep percolation and leaching of nutrients beyond the root zone. Only a portion of the total soil water is readily available for plant use. Plants can only extract a portion of the stored water without being stressed. An availability coefficient is used to calculate the percentage of water that is readily available to the plant. The maximum soil water deficit (MSWD) (also referred to as the management allowable deficit) is the amount of water stored in the soil that is readily available to the plant. The crop should be irrigated once this amount of moisture has been removed from the soil. Once depleted this is the amount that must be replenished by irrigation. It is also the maximum amount that can be applied at one time, before the risk of deep percolation occurs. However, in some cases leaching of salts is desirable and extra irrigation would be desired. IRRIGATION Sprinkler irrigation system operation allows the soil moisture to deplete up to the maximum allowable depletion and then refills the soil profile up to field capacity. The irrigation interval is determined by how long it takes the soil water storage to be depleted to the maximum allowable depletion. The irrigation interval can be a number of days or weeks depending on the climate. Drip irrigation systems are designed and operated to keep the soil moisture content at a level above the maximum allowable depletion by applying water very frequently. An allowable depletion of 25% should be used for agricultural drip systems and 30% for landscape systems. HOW TO DETERMINE THE SOIL WATER STORAGE AND THE MAXIMUM SOIL WATER DEFICIET Step 1 Determine the crop rooting depth, RD (m), Table 1 Step 2 Determine the available water storage capacity of the soil, AWSC (mm/m), Table 2 Step 3 Calculate the total soil water storage, SWS (mm) SWS (mm) = RD (m) x AWSC (mm/m) (Equation 1) Step 4 Determine the availability coefficient of the water to the crop, AC (%), Table 3 Step 5 Calculate the maximum soil water Deficit, MSWD (mm) MSWD = SWS (mm) x AC (%) (Equation 2) Page 1 of 4

14 Table 1 Effective Rooting Depth of Mature Crops for Irrigation System Design Shallow 0.45 m (1.5 feet) Medium Shallow 0.60 m (2 feet) Medium Deep 0.90 m (3 feet) Deep 1.20 m (4 feet) Cabbages Beans Brussels Sprouts Asparagus Cauliflower Beets Corn (sweet) Blackberries Cucumbers Blueberries Eggplant Grapes Lettuce Broccoli Kiwifruit Loganberries Onions Carrots Peppers Raspberries Radishes Celery Squash Sugar Beets Turnips Potatoes Saskatoons Peas Strawberries Table 2 Tomatoes Tree Fruits (spacing 1m x 3m) Tree Fruits (spacing 2m x 4m) Tree Fruits (spacing 4m x 6m) A Guide to Available Water Storage Capacities of Soils Textural Class Available Water Storage Capacity (AWSC) (in. water / in. soil) (in. water / ft. soil) (mm water / m soil) Clay Clay Loam Silt loam Clay loam Loam Fine sandy loam Sandy loam Loamy sand Sand Table 3 Availability Coefficients Crop Maximum Percent (%) Peas 35 Potatoes 35 Tree Fruits 40 Grapes 40 Tomatoes 40 Other crops 50 Page 2 of 4

15 SOIL WATER TERMINOLOGY Available soil moisture Is the difference between the amount of water in the soil at field capacity and the amount at the permanent wilting point. Referred to as the available water storage capacity in Table 2. Saturation Occurs when all the voids in the soil are completely filled with water. Although there is plenty of water available to the crop at saturation, water uptake is seriously curtailed by the lack of oxygen in the soil at soil water contents greater than field capacity. Soil texture Refers to the relative percentage of sand, silt and clay sized particles in the soil material. Soil structure Structure is the arrangement of soil particles and soil aggregates into recognizable particles or lumps. Aggregates occur in almost all soils, but their strength, size and shape varies between soil typed. Field capacity The water content of the soil where all free water has been drained form the soil through gravity. Sandy soils may drain within a few hours but fine textured soils such as clay may take a few days to drain. Proper irrigation brings soil moisture up to filed capacity. Permanent wilting point (PWP) The soil moisture content at which the plant will wilt and die. While there still may be water in the soil, the plant is not able to extract sufficient water from the soil to meet it s needs. Maximum soil water deficit (MSWD) Only a portion of the available water is easily used by the crop. The maximum soil water deficit is the amount of water stored in the plant s root zone that is readily available to the plant. To prevent plant water stress an allowable depletion factor is used to calculate the manageable allowable depletion. This factor varies but is usually around 50%. Deep percolation Water that drains beyond the plant root zone. Saturation Field Capacity Available Soil Moisture Maximum Soil Water Deficit Total volume of water in the soil Permanent Wilting Point Completely Dry Figure 1 Soil Water Moisture Terms Page 3 of 4

16 Example: For a mature corn crop in a loamy sand soil. Rooting depth (Table 1) = 0.90 m Soil Water Storage Capacity (Table 2) = 100 mm/m Availability coefficient (Table 3) = 50% SWS = 0.90 m x 100 mm/m = 90 mm (Equation 1) MAD = 90 mm x 50% = 45 mm (Equation 2) For the same crop in the early summer the rooting depth may be only 0.3 m, therefore: SWS = 0.30 m x 100 mm/m = 30 mm (Equation 1) MAD = 30 mm x 50% = 15 mm (Equation 2) When irrigating the mature crop more water is needed to fill the root zone. When the crop is immature the irrigation amount required will be less. FOR FURTHER INFORMATION CONTACT Janine Nyvall, Water Management Engineer Phone: (604) Janine.Nyvall@gems5.gov.bc.ca RESOURCE MANAGEMENT BRANCH Ministry of Agriculture, Food and Fisheries 1767 Angus Campbell Road Abbotsford, BC CANADA V3G 2M3 Page 4 of 4

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19 Water Conservation Order No Revised October 2001 Agdex 561 CROP COEFFICIENTS FOR USE IN IRRIGATION SCHEDULING Crop water use information can be used to schedule irrigation systems. Crop water use is directly related to evapotranspiration (ET). The ET information must be adjusted to correspond to the crop and climate. This factsheet provides information on selecting the crop coefficient that should be used. Evapotranspiration Evapotranspiration (ET) is a combination of the water evaporated from the soil surface and transpired through the plant. ET can be measured using evaporation pans and atmometers or calculated using climate data. Local climate data for BC can be found on The following nomenclature is often used for reference ET data: ETo - ET calculated using grass as the reference crop ETr - ET calculated using alfalfa as the reference crop ETp - ET measured from a pan or atmometer Figure 1 Elements of Evapotranspiration Once the reference ET has been determined, a crop coefficient must be applied to adjust the reference ET value for local conditions and the type of crop being irrigated. Factsheets Sprinkler Scheduling Using a Water Budget Method and Trickle Irrigation Scheduling Using Evapotranspiration Data provide more information on using ET data to schedule irrigation systems. The tables shown in this factsheet use crop coefficients for use with ET calculated using a grass reference, ETo. These coefficients can be used with ET data from Page 1 of 1

20 Crop Water Use Crop water use is directly related to ET. The crop s water use can be determined by multiplying the reference ETo by a crop coefficient (Kc). The crop coefficient adjusts the calculated reference ETo to obtain the crop evapotranspiration ETc. Different crops will have a different crop coefficient and resulting water use. ETc = ETo x Kc (Equation 1) Where ETo Kc ETc = calculated reference ET for grass (mm) available from = crop coefficient = crop evapotranspiration or crop water use (mm) Crop Coefficients The reference ET is a measurement of the water use for that reference crop. In the case of ETo grass is used as the reference. However other crops may not use the same amount of water as grass due to changes in rooting depth, crop growth stages and plant physiology. The crop coefficient (Kc) takes into account the crop type and crop development to adjust the ETo for that specific crop. There may be several crop coefficients used for a single crop throughout an irrigation season depending on the crop s stage of development. Crop coefficients may also vary depending on how the evapotranspiration data has been calculated or obtained. Reference ET Reference ET is calculated using climatic data obtained from a weather station. ETo is calculated to simulate a grass reference crop. Alfalfa may also be used as a reference crop in some areas and may be referred to as ETr. As a result there are different types of crop coefficients that may be used in the literature. Crop coefficients developed using grass as the reference crops will be larger than those using alfalfa, because ET from alfalfa is greater. The reference ETo obtained from is calculated for a grass reference crop. If using crop coefficients or reference ET values from other sources make sure the Kc value and ET have been developed for use with the same reference crop. Figure 2 Weather Station from Davis Instruments Pan Evaporation Atmometers and evaporation pans also provide ET data. If the ET data used is obtained from a pan or atmometer a pan crop coefficient will have to be applied to convert the pan evaporation ETp to a crop water use ETc. Figure 3 Evaporation Pan and Atmometer Page 2 of 2

21 Converting Crop Coefficients Crop coefficients based on an alfalfa reference or pan reference can be converted for use with a grass reference by using the factors shown in Table 1. The factors shown are for semi arid, moderately windy conditions. For humid, calm conditions the values will be 10% less and for arid windy conditions the values will be 10% more. For most British Columbia summer conditions the factors in the table can be used. Table 1 Guide to Converting Crop Coefficients Based on Reference ET Used Crop Coefficient Conversion Multiply by: Kc - grass (ETo) to Kc alfalfa (ETr) 0.83 Kc - grass (ETo) to Kc - pan (ETp) 0.80 Kc - pan (ETp) to Kc alfalfa (ETr) 1.04 EXAMPLE The Kc value for raspberries in mid season is 1.2 if using a reference ETo for grass. See Table 3. To convert this Kc value for use with an alfalfa reference ETr multiply the value by The crop coefficient for use with an alfalfa reference ETo is: Kc (ETr) = 1.2 x 0.83 = 1.0 Crop Water Use and Stages of Growth Crop growth periods can be divided into four distinct growth stages; initial, crop development, mid season and late season. See Figure 4. The length of each of these stages depends on the climate, latitude, elevation and planting date. Local observations are best for determining the growth stage of the crop and which Kc values to use. For annual crops, during the crop s germination and establishment, most of the ET occurs as evaporation from the soil surface. As the foliage develops evaporation from the soil surface decreases and transpiration increases. For perennial crops a similar pattern may occur as the plant starts to leaf out, grow new shoots and develop fruit. The percentage of canopy cover will determine the rate of evapotranspiration (ET). Maximum ET occurs when the canopy cover is about 60-70% for tree crops and 70- Figure 4 Crop Coefficients and Crop Development Stages 80% for field and row crops. The maximum canopy cover often coincides with the time of year that sun radiation and air temperature are at their greatest. The maximum ET therefore occurs during mid season. During the crop development stage there are no set Kc values. If irrigating during this period choose a Kc value that is between Kc ini and Kc mid. A similar approach should be taken for the time period between Kc mid and Kc end. However this time period may be much shorter and a jump directly from Kc mid to Kc end could be taken. Table 2 provides a description of the various plant growth stages. These stages can be used to select an appropriate crop coefficient from the following Tables. Page 3 of 3

22 Table 2 Crop Stage of Development Initial Stage Indicators Crop Coefficient Crop development Mid season Late Season Planting date (or the start of new leaves for perennials) to 10% ground cover. 10% ground cover to effective full cover, about 60-70% coverage for tree crops and 70-80% for field and row crops. Effective full cover to maturity, indicated by yellowing of leave, leaf drop, browning of fruit. This stage is long for perennials but relatively short for vegetables crops that are harvested for their fresh fruit. Maturity to harvest: the Kc value could be high if the crop is irrigated frequently until fresh harvest or low if the crop is allowed to dry out in the field before harvest. Kc ini Kc ini - Kc mid Kc mid Kc mid - Kc end Select a Crop Coefficient The crop coefficients in Tables 3 and 4 can be used as a general guideline for British Columbia. The crop coefficients are to be used for a grass reference ETo. The crops should be of average height, well watered and well managed. Vegetable and Berry Crops Table 3 provides crop coefficients for various vegetable and berry crops for different stages of the growing season. Crop coefficients for many vegetables may not be available. It is possible to estimate the crop coefficient at the peak time of year for some crops using the ratio of bed width to canopy cover. Comparing crop coefficients of other crops that are similar in nature may also be useful. Kc = Wp/Wb (Equation 2) Where Kc = crop coefficient Wp = width of plant canopy Wb = bed spacing Figure 5 Vegetable Canopy Measurement Page 4 of 4

23 Table 3 Crop Coefficients for Forage, Vegetables and Berries Crop Kc ini Kc mid Kc end alfalfa asparagus beans, green beets blueberries broccoli cabbage cabbage -local carrots cauliflower cranberries celery cereal corn cucumber green onions lettuce Crop Kc ini Kc mid Kc end onions pasture (grass) peas potato pumpkin radish raspberries small vegetables spinach strawberries squash sweet corn sweet peppers tomato tubers watermelon Alfalfa and Other Forage Crops Many forage or hay crops are harvested several times during the growing season. These crops will therefore have a new growth stage cycle for each cut. Instead of one Kc curve for the entire season as in Figure 4, these crops would have a series of curves to make up the entire growing season. See Figure 6. Immediately after a cutting the crop coefficient would revert to Kc ini, 0.3 and the Kc end would end at the next harvest date. The growth stages for the second and third cuts may be shorter than the first cut or the fourth cut. This is because the heat units that are available during the warmer summer months would speed up the growth. Growth during the early spring and fall would be shorter. The crop coefficient for forage crops are shown in Table 3. Figure 6 Growth cycle for forage crops with more than one cut Page 5 of 5

24 Apples and Grapes Crop coefficients for tree fruits and grapes have been segregated into months as shown in Table 4. The absence of a cover crop will lower the crop coefficients shown. The cover crop draws water from the soil storage reservoir and therefore increases water use. If there is no cover crop or grass between the tree or plant rows the crop coefficients will be about 10% lower in May, September and October and 20% lower in June, July and August. Table 4 Crop Coefficients for Tree Fruit and Grapes Crop May June July Aug Sept. Oct. Apples Cherries and Pears with cover crops* Lower Mainland / Vancouver Isl Okanagan / Thompson Kootenays Apricots, Peaches and other Stone Fruit with cover crops* Lower mainland / Vancouver Isl Okanagan / Thompson Kootenays Grapes Lower mainland / Vancouver Isl Okanagan / Thompson Kootenays * No Cover crop reduce values by 10% 20% 20% 20% 10% 10% Soil moisture monitoring devices can be used to adjust crop coefficients to match local conditions. See Factsheet Irrigation Scheduling with Tensiometers for additional information. FOR FURTHER INFORMATION CONTACT RESOURCE MANAGEMENT BRANCH Ted Van der Gulik, Senior Engineer Janine Nyvall, Water Management Engineer Ministry of Agriculture, Food and Fisheries Phone: (604) Phone: (604) Angus Campbell Road Ted.vanderGulik@gems8.gov.bc.ca Janine.Nyvall@gems5.gov.bc.ca Abbotsford, BC CANADA V3G 2M3 Page 6 of 6

25 Water Conservation Order No Revised June 2004 IRRIGATION TIPS TO CONSERVE WATER ON THE FARM Water management is an important part of farm operations and the production of quality agricultural crops. During water shortages, it is important to conserve water and stretch water resources to ensure that the supply will be available for the duration of the growing season. The trick is to ensure the crop has enough water during its growing cycle to maximize yields while not wasting water. Water conservation can be achieved by: using equipment that is more efficient ensuring that equipment is operating properly managing the application of water on the farm more effectively Details on how to conserve water are described as follows: 1. Repair leaks in the irrigation system If you have a water meter installed, the irrigation system can be checked for leaks by turning off the system and monitoring the meter to see if it is still running. Look for perpetual wet spots along the irrigation line that do not dry up between irrigations. 2. Select a more efficient irrigation system if possible Selecting systems that are not as susceptible to evaporation can increase irrigation efficiencies. Using sprinklers instead of a stationary or travelling gun can reduce water use by 5 15%, especially in windy areas. Using a drip system instead of a sprinkler system can save up to 20% of total water use. Page 1 of 2

26 3. Improve sprinkler irrigation efficiency To achieve peak performance, the irrigation system must be properly designed in the first place. Replace old nozzles (checked by using drill bits) and run the system at the designed operating pressure. Ensure that sprinklers are properly spaced. This will improve efficiency and prevent over-irrigation of some areas while trying to cover dry spots. Check the pressure at both the farthest and the highest points of the lateral line. The acceptable pressure variation along a lateral line should be ±10% (no more than 20% variance). 4. Find your maximum irrigation set time and only apply as much water as your soil can hold Soils can only hold a limited amount of water before the water drains below the root zone or will runoff the saturated soil surface. Light sandy soils hold less water than heavy clay soils. See the B.C. Sprinkler Irrigation Manual and the B.C. Trickle Irrigation Manual for more information on how to determine how long to run your irrigation system to minimize water losses. 5. Know your crop s water requirements It is possible to determine how much water your crop is using by monitoring the evapotranspiration (ET) and applying a crop coefficient (K c ). Knowing how much water the crop has used can determine the amount of water removed from the soil. The next irrigation should then only be long enough to replace that amount of moisture. See Factsheet No Irrigation Scheduling Techniques. Local ET information is available at 6. Use a soil moisture monitoring device or climate information to determine when to irrigate Often when the surface of the soil is dry there are still water reserves lower in the root zone that the crop can draw upon. By monitoring soil moisture within the root zone it may be possible to postpone irrigation by a few days. See Factsheet No Irrigation Scheduling Techniques and Factsheet No Irrigation Scheduling with Tensiometers for more information. Climate information is useful in scheduling irrigation. Daily climate data in real-time and a five-day forecast are available at for various climate stations throughout B.C. See Factsheet No Sprinkler Irrigation Scheduling Using a Water Budget Method and Factsheet No Trickle Irrigation Scheduling Evaporation Data for more information. 7. Adjust operating parameters under windy conditions When operating gun systems under windy conditions, lower the trajectory level and/or narrow the spacing to achieve the best uniformity possible. Refer to the B.C. Sprinkler Irrigation Manual for a detailed explanation on how to adjust the spacing based on wind speed. 8. Refrain from irrigating during hot windy periods of the day if possible During the peak of the irrigation season, it may not be possible to wait to irrigate due to the logistics of getting around the entire farm. However, during the early and late part of the irrigation season there may be more flexibility in planning irrigation times. Studies in B.C. have shown that water savings can be realized during the early and late part of the irrigation season, May and June, and also in September. For further information on related topics, please visit our website Resource Management Branch Linking to our Publications and Conceptual Plans FOR FURTHER INFORMATION CONTACT RESOURCE MANAGEMENT BRANCH T. Janine Nyvall, Water Management Engineer Ministry of Agriculture, Food and Fisheries Phone: (604) Angus Campbell Road Janine.Nyvall@gems5.gov.bc.ca Abbotsford, B.C. CANADA V3G 2M3 Page 2 of 2

27 Irrigation Scheduling Order No October 2011 AGRICULTURE IRRIGATION SCHEDULING CALCULATOR The Agriculture Irrigation Scheduling Calculator (AISC) is a water management tool to assist producers in making irrigation decisions. The AISC can be used for any region in British Columbia by selection the closest or most similar climate station on the Farmwest climate network. Background Irrigation systems are designed for the hottest time of the year. The system needs to be able to keep up the evapotranspiration requirement for a specific crop type and geographic location. Evapotranspiration (ET) is a combination of the evaporation of moisture from the soil and plant surfaces and water transpired through the plant. The amount of ET depends on temperature, solar radiation, relative humidity, and wind speed (Figure 1). Figure 1 Evapotranspiration Page 1 of 6

28 Overview During the cooler times of the year the producers will make irrigation decisions based on precipitation and temperature. This is essentially the basis for irrigation scheduling. The Agricultural Irrigation Scheduling Calculator was designed to assist producers in making scheduling decisions based on a more scientific approach. The Irrigation Industry Association of British Columbia (IIABC) applied for funding though the National Water Supply Expansion Program to develop the calculator. The Province of British Columbia provided the expertise and support. The IIABC is the owner of the Agricultural Irrigation Scheduling Calculator. The Agricultural Irrigation Scheduling Calculator (AISC) is designed to work with multiple types of crops and irrigation systems. To begin using the AISC an account is created with a password to protect personal data. Then the field and geographic location are entered. Now the crop, soil type, and irrigation system parameters are selected. After this is done the calculator can now determine and irrigation schedule for that field. Using the Calculator The calculator is found on the IIABC website, To use the AISC click on the Agriculture icon (Figure 2). New Users will be required to create an account. When this is done the producer can then start entering field data. Multiple fields and system can be store for quick retrieval in the calculator. The calculator does have both metric and imperial measurements. Help icons, indicated by a question mark, are found in the calculator where data input is required. The calculator has a four step process for entering data. Figure 2 Agricultural Icon Page 2 of 6

29 Step 1 Crop Type The first item entered into a new system is the crop type. Each crop type has an effective rooting depth, availability coefficient and climate coefficients associated with it. Effective rooting depth, which is the top 50 percent of the rooting depth, vary from shallow (1.5ft) to deep (4ft). The availability coefficient (AC) represents the percentage of water the crop can draw from the soil and continue to have productive growth. The AC varies from 35 to 55 percent (Figure 3). The crop climate coefficients represent the plants different consumptive rate for water through the growing season. Table 1 Rooting Depth (RD) and Availability Coefficient (AC) RD RD Crop AC Crop AC [ft] [m] [ft] [m] Alfalfa Hops Almonds Kiwifruit Asparagus Lettuce 1 1/ Beans, green Loganberries Beets Onions, green 1 1/ Blackberries Pasture species 1 1/ Blueberries Peas Broccoli Peppers, sweet Brussel Sprouts Potato Cabbage 1 1/ Pumpkin Cantaloupe Radishes 1 1/ Carrots Raspberries Cauliflower 1 1/ Spinach Celery Squash Cereals Strawberries Clover (ladino) 1 1/ Sugar Beets Clover (red) Tomato Corn, field Tree fruits (12 ft x 18 ft) Corn, sweet Tree fruits (3 ft x 10 ft) Cucumber 1 1/ Tree fruits (6 ft x 12 ft) Eggplant Turf 1/ Garlic 1 1/ Turnip 1 1/ Grapes Figure 3 Rooting Depth and Availability Coefficient Step 2 Soil Cross Section The second set of information entered is the soil type and depth (Figure 4). Each soil type has a different water storage capacity. Multiple layers of soil can be entered. It is recommended to have the soil professional tested for classification. Figure 4 Soil Type Page 3 of 6

30 Step3 Irrigation System Design The third set of data to enter is the irrigation system information (Figure 5). Multiple types are available and all agricultural systems other than flood are covered. It is very important to enter correct information on each system type. Incorrect spacing, nozzle size or pressure can make a large difference in the output of the calculator. The required information may be available on the original design if available, but often changes have been made in the system. Warning notices may appear if incorrect information is entered. Figure 5 Irrigation System Details Step 4 Irrigation Scheduling The calculator is now ready to output an irrigation schedule. To begin the process the weather station which is entered earlier can be changed if desired. The weather stations are on the Farmwest network which has about 100 locations. It will be expanding to other provinces in the future. Now the date that the irrigation cycle was started on can be selected from a drop down calendar. The calculator also allows the producer to go back in time to look at previous years if the climate data is available (Figure 6). Figure 6 Irrigation Cycle Date Page 4 of 6

31 After the start date has been selected the calculator will determine the irrigation schedule. The result will show the daily ET and a forecast for the next five days. The calculator outputs two types of results. For most systems it is the time before the next irrigation should occur (Figure8). For drip systems it is the operating time for the zone (Figure 9). User Guides For more detail on using the Agricultural Irrigation Scheduling Calculator, User Guides are available on the IIABC web site (Figure 7). Figure 7 User Guides Page 5 of 6

32 Figure 8 Irrigation Schedule for Sprinkler System Figure 9 Irrigation Schedule for Drip System SUSTAINABLE AGRICULTURE MANAGEMENT BRANCH WRITTEN BY Ministry of Agriculture Andrew Petersen, P.Ag Angus Campbell Road Regional Resource Specialist Abbotsford, BC V3G 2M3 Phone: (604) or Kamloops Office Page 6 of 6

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34 Agriculture and British Columbia s WATER PLAN In June 2008 the province released Living Water Smart, British Columbia s Water Plan. The plan provides a road map or direction for water management in British Columbia and makes a number of commitments that will be achieved over the next few years and beyond. Goals that are established with respect to agriculture include: Farms and ranches will have enough water to irrigate their crops Agriculture will use efficient irrigation methods Crops suited to our soils and climate will be grown Preserve top soil to absorb and retain water Where possible use reclaimed water Improve stream health and restore stream banks and riparian areas Keep animals out of waterways Use fertilizers, pesticides and compost properly to take of our soils and water Capture runoff and ensure only clean water enters creeks and streams The Water Plan also makes the following commitments: By 2020 water use in the BC will be 33 percent more efficient By 2012 all large water users will measure and report their water use Government will secure access to water for agricultural lands The agriculture sector will need to be more efficient By 2012 new approaches to water management will address impacts from increased drought risk and climate change Adapting to climate change and reducing impacts on the environment will be a condition for receiving provincial infrastructure funding Developments on flood plains must be flood proofed to high provincial standards Wetland and waterway function will be protected Fifty percent of new municipal water needs will be acquired through conservation by 2020 Government will expand BC s hydrometric and climate station network Government will publish a report on state of the water by 2012 and every 5 years after that The Okanagan Basin Water Board has developed a Sustainable Water Strategy for the Okanagan Basin. The strategy builds on many of the initiatives that have been outlined in the Living Water Smart plan. Action items that are identified in the plan that are oriented to agriculture include: Manage livestock in watersheds through the installation of fencing at key locations and the provision of off-stream watering facilities Establish an Agricultural Water Reserve that links agriculture water budget allocations to the ALR. Extend the date on irrigation licences to allow for irrigation later in the season Implement drought management planning based on a provincial template Prepare a comprehensive water management plan for the Okanagan Basin Use certified irrigation designers to design systems Prepared by Sustainable Agriculture Management Branch

35 Where appropriate maintain affordable agricultural water rates by splitting systems, increasing use of treated wastewater, implementing education and incentive programs Ensure water storage is identified as a strategic and critical component to water management in the Okanagan Maintain and expand the network of hydrometric and climate stations operating in the Okanagan The Ministry of Agriculture and Lands has developed an Agriculture Plan Growing a Healthy Future for BC Families. Strategy 8 of the plan identifies the need to integrate agriculture in provincial water management policies and programs. The plan calls for: Processes that provide clarity to agricultural users about sustainable water withdrawals Management of environmental impacts Establishing reserves for agricultural land Funding programs for water infrastructure Programs encouraging water conservation and leadership on water use efficiency Work with local, regional and federal governments to address long term flood control measures The above documents and plans provide direction for a water plan in British Columbia and guidance on issues that need to be resolved for agriculture. The list of issues in this document were formed and based on these plans. A meeting of Ministry of Agriculture and Lands staff, other agencies and the British Columbia Agriculture Council ranked each issue with respect to risk and consequence and those are shown on each note. This document is draft and a work in progress please provide comments, suggestions, corrections thoughts and ideas on implementation or action. Information on resources and costs have been left out at this time however suggestions on this section can be offered. Comments can be forwarded to Ted van der Gulik, P. Eng Senior Engineer at the following: Ted.vandergulik@gov.bc.ca Phone: Cover Photo taken by Barry Smith at Oyama, British Columbia Prepared by Sustainable Agriculture Management Branch