WATER REQUIREMENTS FOR GRAPE VINES Andrew Teubes Viticultural Consultant
Water requirements Most important principles are: Know the symptoms on the vine of water stress Know the physiological stages when a lack of water will affect the size and quality of the crop Know the depth and size of the root system Know the soil in order to know what the storage capacity of the soil is for water Know how much water to apply
Know the depth of the rooting system
Know the depth of the rooting system
SOIL TYPES Alluvial sandy soil with different layers of sand and silt. Clay content <5% Water retention capacity <50 mm/m Irrigate every 7 days
SOIL TYPES Deep, well drained red soil of high physical potential, but with low ph. Clay = 15-20% Irrigate every 20 days
Types of water Types of water in the soil Gravitational water Free drainage after irrigation/rainfall Drainage water Available water (between field capacity FC and permanent wilting point PWP) Easily available Difficult available Non available water Too dry for soil to use
GROWTH STAGES 80-90 days 30-50 days 60-100 days Bud break Flowering Fruit set Pea size Berry softening Harvest Leaf fall Dormancy
Critical physiological stages Prior to bud break in dry regions without winter rainfall (Dormant phase) During winter the vine is dormant, low water use Keep moist for risk of frost/freezing Important for even bud break and shoot growth leading up to the flowering period
Critical physiological stages Bud break to before flowering Relatively low water requirement because lower spring temperatures and small leaf area Shoots are only point of demand 35-50 days
Critical physiological stages Flowering and fruit set up to pea size Key time for good supply of water Phase 1 of berry growth Influences fruit set Influences berry development (cell division) that determines final crop size Period 3-4 weeks after set 20-30 days
Critical physiological stages Pea size to berry softening Phase 2 of berry growth Not as critical as phase 1 Slower rate of growth lag phase of berry growth 30-40 days
Critical physiological stages Ripening (berry softening to harvest) Phase 3 of berry growth Starts with softening, coloration of berries Fast increase in volume due to cell enlargement, increase in sugar levels, decrease in acidity (high metabolic activity) Very high water requirement in this phase Maintain easily available water levels high 25-45 days
300 BERRY DEVELOPMENT Phase 2 Phase 3 BERRY SIZE 250 200 150 100 50 Bud break Fruit set Phase 1 Pea size Berry softening No stress Stress at set Harvest 0 GROWING SEASON
Critical physiological stages After harvest Building of reserves for next season Period of active root growth Maintain adequate moisture levels, but do not encourage any active growth that can utilize reserves (very dangerous for freeze damage) Leaves should remain active only Manage the ripening of the shoots for protection against winter chilling
Most important stages 1. Flowering period Priority 1 2. Berry softening Priority 2 3. After harvest- Priority 3 If adequate water is available, irrigate during 1, 2 and 3 If enough water is available for only 2 times, irrigate during 1 and 2 If enough water is available for only 1 time, irrigate then only during 2
Symptoms of water shortages Irrespective of the previous critical physiological stages; vine will show physical symptoms of water shortages Important to recognize the symptoms to know when the vine requires irrigation Growing tip pulls back Growing tip pulls back - 1 Tendril orientation sags - 2 Leaf orientation away from sun 3 Leaf petioles start to sag - 4 Yellow leaves in cluster zone 5 Berries shrink - 6
Reduced growth (elongation of shoots) Importance of tendrils 1 2 3
Tendril 2 from growing tip sags - 450 kpa - 600 kpa - 1220 kpa No stress Mild stress Increased stress
Growing tip stops completely First leaf below tip folds over growing tip
Leaf orientation away from sun Leaf blade folding to inside
Leaf blade petioles start to sag past 90 Brown and yellow leaves in cluster zone Clusters have greyish green colour
Severe drought stress Foliage Cluster
Practical methods for evaluating soil moisture Various systems can be used to evaluate the soil moisture Important facts Know the rooting depth (make profile pit)
Tensiometers Neutron probe Resistance blocks
Feeling the soil Take soil sample in hand and squeeze it
SOIL MOISTURE FEEL TEST
Soil moisture indicators for the FEEL TEST
Evaluating soil moisture Most of feeder roots are in top soil Plant extraction of water is 40% from the top 25% of rooting zone
Types of irrigation Full surface wetting Flood systems Cover total soil area Furrow Overhead sprinkler systems Micro jets Concentrated wetting Drip systems
Flood irrigation full surface 200 m³/hour/ha
Flood irrigation - furrow
Overhead sprinkler 80-100 m³/hour/ha
Micro sprinkler 60-70 m³/hour/ha
Drip irrigation 10-20 m³/hour/ha Water distribution of drip Sand Loam Clay
Water movement in the soil The longer you irrigate, the deeper the water will penetrate
Water penetration time Rate of water infiltration depends on soil type and volume of water applied Flood irrigation examples Sand: 300-400 mm per hour Loam: 150-250 mm per hour Clay: 30-50 mm per hour
How long must I irrigate? Length of time of flood irrigation depends on Strength of water current from canal Length of furrow Width of furrow Rooting depth (depth of water penetration) Infiltration time to required depth Water losses through evaporation, drainage, etc If the above information is not available it will be very difficult to determine the correct time of an irrigation Practical answer is to apply irrigation and to make a profile pit to determine the depth of wetting after 2 days
When to irrigate? Depends on: Physiological stage Soil type (water holding capacity) Climate (temperature, relative humidity, wind) Type of irrigation (flood, sprinkler, drip) Water quality Most important Availability of water (how much and when available) Experience
Decisions Afghanistan situation Irregular supply of water for irrigation Mostly flood irrigation Risks of increased diseases with irresponsible water applications Soil type Sandy: more regular water applications Clay: less regular water applications
Practical methods to determine timing and size of irrigation Example flood irrigation What do I need? Evaporation figures (Class A pan) Long term weather data? Estimation of soil water holding capacity Plant factors Depletion level of soil water Effectiveness of irrigation system Water volume
Flood irrigation example Evaporation=Amount of water that evaporates from an open water surface every day Obtained from direct measurement (Class A pan) that is ideal Obtain from long term weather data
Class A evaporation pan
Flood irrigation example Crop factor=ratio between evaporation from the soil surface and transpiration by the vine Experimentally calculated for different regions E(t) = E(o) x f E(t)=evapotranspiration (water use by plant) E(o)=evaporation (measured by Class A pan) f=crop factor
Plant factors for table grapes Month Plant factor December-March 0.15 April 0.2 May 0.4 June 0.6 July 0.6 August 0.6 September 0.4 October 0.3 November 0.2
Flood irrigation example Estimated water holding capacity Sand 50 mm/m Sandy loam 75 mm/m Loam 100 mm/m Silty clay 125 mm/m Clay 150 mm/m
Flood irrigation example Depletion level of soil water Table grapes never below 50% during the active growing period (April-September) Can come down to 40% within 3-4 weeks after harvest Can come down to 30% during the dormant phase in winter
Flood irrigation example Effectiveness of irrigation system Water losses through mostly evaporation Also soil canals, pressure loss Flood =60% Sprinkler =80% Drip =90%
Flood irrigation example Month: July Water holding capacity of soil: 100 mm/m Evaporation figure Thus per week =11 mm/day =77 mm Plant factor =0.6 Thus 77mm x 0.6 =46.2 mm replace every week
Flood irrigation example 50% depletion level for active period Thus 100 mm/m available water x 50% =50mm (when this amount of water was used, the 50% level will be reached) Time for the next irrigation Compensate for flood effectiveness, thus 50mm/60% =83 mm 46.2 mm is used every 7 days Thus irrigation is required roughly every week
Flood irrigation example How long must the irrigation continue? Flood systems normally delivers between 100 and 200 m³ per hour Calculates to between 10 and 20 mm/hour/ha At 100 m³/hour, it requires the system to run for approximately 8 hours to irrigate 83mm per hectare
Water quality Grapevines have moderate to good resistance to salinity Water for irrigation containing saline salts and/or elements has direct and indirect effects on the plant Direct: Uptake of nutrients Indirect: Physical effect on the soil
Water quality What is important for water quality? Sodium (Na+) <120 ppm (80) Chlorine (Cl-) <150 ppm (80) Conductivity (EC) <170 ms/m (100) TDS <1000 ppm (640) Bicarbonates (HCO3-) <120 ppm (80) Boron <1 ppm (0.3)
Summary Vines have a high requirement for water during Flowering and fruit set At berry softening After harvest Know the symptoms of water stress Make regular holes in the vineyard to feel the water content of the soil Irrigation is a valuable tool to optimize vine performance for quantity and quality