Hot Climate & Irrigation Flashcards
Which meteorological factors determine grapevine physiology (incl. phenology), its
production system and, to a certain extent, the varietal profile? (POTENTIAL EXAM QUESTION)
-Growing season temperature
-Wind
-Evapotranspiration
-Water balance
-Soil temperature
-Radiation
How does heat affect productivity, quality and production system? (POTENTIAL EXAM QUESTION)
Productivity:
-High crop loads and hot ripening may cause carbohydrate reserves to decline during ripening
-Soil temps > 33C can damage roots
-Heat waves can burn leaves, shoot tips, and berries
Quality:
-Temps > 30C reduce the biosythsis and increased degredation of anthocyanins
-Decrease in total acidity (malic and tartaric), increase in pH
Production Systems for Hot Climates:
-Row orientation N/S for morning sun and afternoon shade
-Irrigation to cool grapes and maintain productivity
-Nightime harvesting (for fruit and people)
-Canopy management with adequate shading
-Drought tolerant rootstocks
-Mulch or soil cover to conserve moisture
-Shade cloth
Which are the main differences between the production systems of hot and more moderate
climates, and why do they exist? (POTENTIAL EXAM QUESTION)
Hot Climate:
-Lower vine density
-Vines trained up to wire over 3 years
-Spur pruning
-Adequate shading
-Harvest determined by juice quality
-Irrigation
-Rootstocks selected for phylloxera, nematodes, salinity, vigor control, heat and drought tolerance
-Fertilization post harvest to aid in carbohydrate reserves
Cool Climate:
-Narrow row/vine spacing = higher vine density
-Cane pruning
-Sun exposure for ripening
-Harvest determined by sanitary state
-Higher disease pressure = more spraying
-permanent or part-time cover crop, depending on percipitation
How can we determine irrigation demand and what are advantages/disadvantages of the different approaches? (POTENTIAL EXAM QUESTION)
- Soil based measurements: probes, tensiometers, watermark sensors
Advantage:
-low cost
-real time data
Disadvantage:
-doesnt meaure whole root zone
-difficult in rocky soils
-interpretation of data challenging
- Plant based measurements: sap flow, pressure bomb, thermal imaging
Advantages:
-measures plant directly
-integrates soil water availability, root distribution and uptake effectiveness
Disadvantage
-vineyard is a harsh environment
-labor intensive for pressure bomb
-sap flow values difficult to relate to wine water requirements
-interpretation of thermography difficult
- Climate based methods: evapotranspiration models
Advantages:
-Low cost
-Used at a region wide level
-Doesnt require instrumentation in vineyard
Disadvantage:
-general calculations may not be accurate for all vineyards
-refinements for soil type, canopy size, cover crops
- Remote sensing: vegetation indicies, UAV based images
Advantages:
-large areas covered with high spatial resolution
-UAV based images are cloud independant
Disadvantages
-interference of other growth limiting factors (like nitrogen)
-vegetation like cover crops can cause for error
How do viticultural interventions and stress influence source/sink ratios and grapevine
physiology? (POTENTIAL EXAM QUESTION)
Photosynthate (source: leaves)
Demand from growing tissue (sink: fruit, roots, shoots)
▪ Stress modifies resource partitioning within the plan
▪ Sinks are donwregulated earlier than sources upon C-limiting stress
Interventions and stress shift the balance, either enhancing or restricting fruit development
Viticulture Interventions:
Irrigation - control water stress and influence stomatal behavior (source) & sugar transport (sink)
Cluster thinning - reduces competition, increases resource (source) allocation to remaining fruit (sink)
Leaf removal - alters the balance between leaf (source) and fruit development (sink), impacting sugar accumulation
What is “optimum resource allocation”? (POTENTIAL EXAM QUESTION)
The plants strategy of distributing resources to the organ that can best alleviate a deficite during stress or responce to environmental conditions.
-Alleviating deficites: directing resources (carbs and nutrients) to plant parts that can most effectively address the stress
-Light stress: plant compensates by increasing leaf area (regardless of N supply)
-Drought stress: dry matter (carbs, proteins, lipids, cell wall components) is redirected towards essential functions like root growth.
-Hormonal Signals: Abscisic acid (ABA) and cytokinins play a role in signaling and regulating resource allocation, as seen in Partial Rootzone Drying where the ABA to cytokinin ratio in roots changes
Explain carbohydrate allocation in the course of a viticultural season:
-Carbohydrate reserves are essential for establishing spring canopy
-50-75% of carbs are stored in roots
Spring: initial canopy developemtn
Ripening: In hot climates, high crop loads combined with high temperatures during ripening may lead to a decline in carbohydrate reserves
Post-Harvest: critical time for replenishing reserves (especially in warm climate). Fertilization is often conducted after harvest to aid
Cool climate: carb reserves are typically restored by harvest
Hot climate: carb reserves typically depleted, critical post harvest to replenish
Factors affecting carbohydrate allocations:
-crop load (deplete storage)
-temperatures (less photosynthesis)
-water & nutrient availability (needed to support photosynthesis and carb production)
What are the physiological responses to stress and viticultural interventions?
Hormonal Regulation:
-Abscisic acid (ABA) increases under drought stress, promoting stomatal closure and reducing transpiration.
-Cytokinins regulate shoot and root growth, influencing sink demand during stress conditions.
Nutrient Remobilization:
Especially nitrogen and carbohydrates are redirected based on sink demand, affecting vine vigor and fruit quality.
Leaf Senescence:
Reducing photosynthetic capacity (source limitation).
Xylem Hydraulic Failure:
Extended stomatal closure leads to hydraulic failure, reducing water transport and impacting overall vine health.
What are the climate indices?
- Average growing season temperature:
April-October - Growing degree days:
Sum of average daily temperature above base value (10C) - Huglin index:
Sums estimate of daytime temperature above 10C with latitude correction. - Cool nigh index:
Average minimum temperature of harvest month - Winkler index:
Sum of average monthly temperature above 10C April-Oct - Biologically active degree day index:
“Capped” Index (10-35C) Sums estimate of daytime temperature above 10C with
latitude correction. T above threshold do not accumulate GDD. April-Sep
