wind and plants. wind wind has a major effect on agricultural and horticultural production in nz. ...

Wind and PlantsWind and Plants

WINDWIND

Wind has a major effect on agricultural and horticultural production in NZ.

The prevailing winds are the most common winds in an area.

NZ has a westerly wind pattern due to the earth’s spin. This is changed in some areas by local features and topography.

The ranges to the north and the mountains to the sough turn the westerlies blowing towards Wellington into northerlies as they flow through Cook Strait.

Strong moist northerly winds are common in Wellington in spring, these damage blossom and new plant growth.

WindWind

Wind can be measured using the Beaufort scale.

Effects of wind on plant Effects of wind on plant productivityproductivity

Structural damageStructural damage LodgingLodging – flattening of cereal crops – flattening of cereal crops CuticleCuticle damage on leaves – increases damage on leaves – increases

water losswater loss Broken Broken branchesbranches Loss of Loss of petalspetals on flowers on flowers SoilSoil displacement causing soil erosion displacement causing soil erosion

Physiological damagePhysiological damage

Removal of the layer of humid air around Removal of the layer of humid air around the leaves which forms a protective the leaves which forms a protective environmentenvironment

This causes:This causes:

Physiological damagePhysiological damage

Removal of the layer of humid air around Removal of the layer of humid air around the leaves which forms a protective the leaves which forms a protective environmentenvironment

This causes:This causes: High winds remove humidity

Increase in transpiration Water stress

Loss of productivity

Guard cell close CO2 cannot get in Less photosynthesis

•Increased erosion and removal of topsoil as dust. _

For each of the following problems, make notes on why it is not good. Wind can cause many problems including:

Lodging of plants (when leaves become entangled), making them difficult to harvest

Spreading weed seeds, meaning more costs of removal, or lower income due to contamination of seed crops.

Reduced or damaged plant growth. Damaged leaves do not carry out as much photosynthesis. Flowers can be damaged or blown off the plant. Wind-damaged fruit does not store as well and is less marketable. Cuticle damage to leaves causes an increase in water loss.

Upsetting insect movement.

May bring salt spray or cause spray drift

Positive effects of the wind:

Reduced likelihood of frost Providing air movement that will dry the

outer leaves of a plant and therefore prevent the growth of fungal diseases

Assisting with the pollination of wind pollinated plants

Aid the drying of hay or grains before harvest.

Activity on wind page 45Activity on wind page 45

Correct orderCorrect order

NZ is a fairly windy placeNZ is a fairly windy place Wind is caused byWind is caused by An anticycloneAn anticyclone Near the Earth’s Near the Earth’s Over elevated Over elevated

Activity page 46Activity page 46

Answers for pg 46Answers for pg 46

Defoliation – stripped of leavesDefoliation – stripped of leavesIncreased transpiration – leaf scorchingIncreased transpiration – leaf scorchingAbrasion – sand particlesAbrasion – sand particlesRoot damage – plant rocking in groundRoot damage – plant rocking in groundBranches rub – scarring on branchesBranches rub – scarring on branchesPlant distortion – plant leaning awayPlant distortion – plant leaning awayLodging – the flattening of cereal cropsLodging – the flattening of cereal cropsReduction in pollination – loss of petalsReduction in pollination – loss of petals

Fruit loss – apple windfallsFruit loss – apple windfallsFruit loss, knocked off tree – pears Fruit loss, knocked off tree – pears

downgradeddowngradedWater loss – wilting of plantWater loss – wilting of plantInterference with insect movement – bees Interference with insect movement – bees

cannot flycannot flyCrop maturation – harvesting time laterCrop maturation – harvesting time laterSpraying – drifts from your property to Spraying – drifts from your property to

anotheranother

Lessens humidity – perfect disease free Lessens humidity – perfect disease free cropcrop

Reduces chance of frost – Large open areasReduces chance of frost – Large open areas

Increase in wind pollination – grass pollenIncrease in wind pollination – grass pollen

Guard cells – the stomata changes shapeGuard cells – the stomata changes shape

Techniques to modify windTechniques to modify wind

Artificial Shelter Artificial windbreaks are expensive to set

up and are often used for high value or short term crops.

The strongest likely wind has to be considered along with the soil type to prevent the support posts blowing over.

Advantages

a crop has instant sheltera crop has instant shelter usually low maintenanceusually low maintenance takes up little spacetakes up little space does not use up soil water and nutrientsdoes not use up soil water and nutrients Does not have many of the disadvantages Does not have many of the disadvantages

of live shelterof live shelter

Disadvantages

require replacing after several years due to damage from light and wind

not biodegradable creating disposal problems

expensive Does not have many of the advantages of

live shelter

Wind Break Design

1. Permeable windbreaks are more effective at 1. Permeable windbreaks are more effective at reducing the force of wind than a solid barrier.reducing the force of wind than a solid barrier.

Live shelter should be triangular in vertical cross Live shelter should be triangular in vertical cross section – this shape will reduce turbulence on section – this shape will reduce turbulence on the leeward side and cast less shadow. the leeward side and cast less shadow.

If the windbreak is impermeable, turbulence is aIf the windbreak is impermeable, turbulence is a possibility on the leeward side. possibility on the leeward side. This is because the wind goes up and over the This is because the wind goes up and over the

impermeable object.impermeable object.

2. Areas with heavy snow drifts are protected by thicker shelter belts in the form of a small woodlot.

3. Distance between windbreaks should be no more than 20 times the height of the windbreak to prevent the build up of unsheltered windspeed.

Large shelter is often planted around perimeters of blocks and subdivided with artificial shelter.

4. Planting in double rows to allow:

• reduction of draughts below taller shelter.

• replacement trees for older shelter belt.

5. In frost areas, where shelter is planted across valleys to prevent wind tunnelling, either deciduous shelter or gaps are used to allow cold air to drain away.

6. Plant shelter across valleys to prevent 6. Plant shelter across valleys to prevent wind tunnellingwind tunnelling

7. Run windbreaks north –south where possible to reduce shading

Student activitiesStudent activities

Page 88 - 89Page 88 - 89

Answers to student activityAnswers to student activity

1.1. 14% at 8m14% at 8m

2.2. Air temp – 16% at 1m, soil evap - -40% Air temp – 16% at 1m, soil evap - -40% at 3m, relative humidity – 8% at 1m, soil at 3m, relative humidity – 8% at 1m, soil moisture – 20% at 1m, wind speed -60% moisture – 20% at 1m, wind speed -60% at 4mat 4m

3.3. Air temp 2%, soil evap -25%, relat. Air temp 2%, soil evap -25%, relat. Humid -0%, soil moisture 3% and wind Humid -0%, soil moisture 3% and wind speed -45%speed -45%

4.4.