TEMPERATURE AND PLANT GROWTH

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TEMPERATURE AND PLANT GROWTH
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What is Temperature?

• Temperature is the measurement of how hot
  something is.
• In NZ we measure temperature in degrees Celsius
  (oC).
• The minimum temperature is how low the
  temperature will go, whereas the maximum is the
  highest it will go.
• Temperature fluctuates throughout the day, and
  throughout the year.
• The temperature has effects on plants.
• Plants need certain temperatures in which to
  flourish.
• All plants have an optimum temperature at which
  they function best.

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Student Activities

• Read pg 20 and highlight the key ideas.

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Key Ideas

• NZ has a temperate climate
• NZ does not have a large temp. range.
• January and February are the warmest months, July
  is the coldest.
• The highest summer temps. Are usually recorded on
  the east coast of the South Island.
• The far north has more subtropical weather.
• Temp. increases as altitude decreases and air
  temp. can be changed by features such as slopes
  and wind currents around mountain ranges.

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Air Temperature

• Read through page 21 and answer the questions.
• Read page 311 332 in Dynamic Ag.

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Answers

• 2. Hawkes Bay
• 3. Central Otago
• 4. Central Otago
• Read page 23 in workbook
• Use the following slides to fill in the effects
  of temp. on plants.

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Growing Degree Days

• Temperature on its own has been found not to be a
  reliable indicator of an areas suitability for
  growing a particular crop.
• Growing degree days, however, have been found to
  be a better indicator.
• Researchers have found that plants need a certain
  amount of heat to survive.
• This is known as the base (minimum) temperature
  or threshold temperature for that particular
  plant. For maize this is 10o.

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• In the absence of extreme conditions such as
  unseasonal drought or disease, plants grow in a
  cumulative stepwise manner which is strongly
  influenced by the ambient temperature.
• Growing degree days take aspects of local weather
  into account and allow gardeners to predict (or,
  in greenhouses, even to control) the plants pace
  toward maturity.
• Unless stressed by other environmental factors
  like moisture, the development rate from
  emergence to maturity for many plants depends
  upon the daily air temperature.
• Because many developmental events of plants and
  insects depend on the accumulation of specific
  quantities of heat, it is possible to predict
  when these events should occur during a growing
  season regardless of differences in temperatures
  from year to year.
• Growing degrees (GDs) is defined as the number of
  temperature degrees above a certain threshold
  base temperature, which varies among crop
  species.
• The base temperature is that temperature below
  which plant growth is zero.
• GDs are calculated each day as maximum
  temperature plus the minimum temperature divided
  by 2 (or the mean temperature), minus the base
  temperature.
• GDUs are accumulated by adding each days GDs
  contribution as the season progresses.

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• GDUs can be used to assess the suitability of a
  region for production of a particular crop
  estimate the growth-stages of crops, weeds or
  even life stages of insects predict maturity and
  cutting dates of forage crops predict best
  timing of fertilizer or pesticide application
  estimate the heat stress on crops plan spacing
  of planting dates to produce separate harvest
  dates.

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• Barley Hordeum vulgare125-162 GDD to emergence
  and 1290-1540 GDD to maturity
• Wheat (Hard Red)Triticum aestivum143-178 GDD to
  emergence and 1550-1680 GDD to maturity
• Oats Avena sativa1500-1750 GDD to maturity
• Corn (maize) Zea mays2700 GDD to crop maturity

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Base temperature for some crops and pasture
plants.
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Growing-Degree-Days (4C base temperature) for
long-term weather stations in New Zealand.
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• Note anomalies can occur when you have a cloudy
  day at say 15C and then the sun comes out for 15
  minutes.
• The temperature climbs by 8 - 10C, causing a
  sudden spike on the graph giving a not so
  accurate picture of GDDs for that particular day.
• The most accurate method, costing about 300 per
  unit, is to install a data logger that takes
  automatic temperature readings every 30 minutes
  and can store up to 6 months data. This will
  smooth out any variations.
• The growing degree days required to produce
  quality cherries is 800.
• As a comparison, apples require a minimum of 700
  GDDs, with grapes and olives needing 900 GDDs.
• Ideal growing temperatures for cherries are
  between 10C 30C, with temperatures above and
  below this range limiting growth.

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Read through pg 24

• Attempt the questions on GDD

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Answers

1. The number of days that the plant is able to grow
2. Growing degree days take into consideration
   seasonal variations whereas calendar do not.
3. The plant does not grow below that temperature.
4. Central Otago 966 and Hawkes Bay 1642

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• 5. Hawkes Bay
• 6. In a year where there is low sunshine there
  may not be enough growing degree days for the
  crop to mature and ripen.
• 7. Tauranga has 1365 growing degree days. So
  using the 1300GDD column and the 20th of
  September column they intercept on the 8th of
  February.
• 8. It is just coming out of spring and the days
  are still low in temp, therefore there are not
  many days in September above 10o C, so it takes
  longer to reach the required growing degree days.

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1. Sweet corn are frost tender, so planting later
   will reduce the risk of frost. Sweetcorn also
   requires a soil temperature of 12oC, so by
   planting a month later increases the soil
   temperature. Planting a month later means
   harvest is only 3 days later.
2. Nelson has 1090 growing degree days. So using
   the 1000GDD coloumn, the earliest he can 0plant
   his peas is the 1st of September.

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SOIL TEMPERATURE

• Air temp the cooler
• Aspect soils on slopes
• Climate Drier climates
• Season- in the summer
• Soil Colour soils that are dark
• Soil depth soils that are deep
• Soil texture soils such as sandy
• Vegetation cover soils that are covered in
• Water availability- soils that are wet

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Frosts

• Read pg 29 in your workbooks
• Fill in the gaps

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Frost answers

• What are frosts? still, radiation, wind,
  southerly
• Frost behaviour warm, shelterbelts, altitude
• Measuring frosts air, ground
• Negative effects of frosts water, higher, cell,
  plant, nutrients, frost, flowers, leaves, crop,
  fruit
• Positive effects pests, chilling

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Videos

• Worksheets

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