1. Unit 3: Water Chapter 6

2. Unit 3: Water Unit 3 Objectives: Understand the role and characteristics of water Knowledge of the concepts of transpiration and its relationship to plant water needs Plant water needs Explain water movement within the plant Describe symptoms of water shortage

3. Unit 3: Water Characteristics of Water Ex. A 1 ton load of fresh cut alfalfa would weigh only 520 lbs. w/out the water What molecules combine to form water? How much of each? Exists in 3 forms Liquid - 32° - 212°F Vapor - >212°F Solid - <32°F

4. Unit 3: Water Resistant to temperature changes Requires the most heat energy to raise temp 1°C Universal solvent Can dissolve almost anything Powerful, yet gentle Dissolve rock Hold an enzyme, medium for biochemical reaction

5. Unit 3: Water Water is the determining factor regardless of the temp zone Productivity Growth Survivability Role of Water Necessary part of cells and tissues Biochemical medium that helps move and dissolve nutrients from roots to shoots, and storage

6. Unit 3: Water Chemical reactant in chemical processes (photosynthesis) Cell turgor Responsible for stomata function and maintaining plant turgidity Coolant/temp buffer

7. Unit 3: Water Plant classification based on their water needs Xerophytes – grow in dry places Conserve/store water Ex.? Sorghum, millet Mesophytes – grow in moderately wet areas Most cropping plants Hydrophytes – best in very wet/flooded regions Water lily Rice

8. Unit 3: Water Precipitation Precipitation forecasts are most useful for planning Measurable precipitation must be.01” or more Weather forecasters calculate the probability of rain within a system and the area by which it may cover

9. Unit 3: Water Computer modeling is now very common to help predict rain, amounts, etc. Help make management decisions on: Planting Harvesting Irrigation Weather Outlooks 6-10d 30d Longer?

10. Unit 3: Water Normal temp and precipitation is a 30yr. Avg. calculated every 10 yrs. Water Loss in Plants Directly proportional to the amount of exposed surface area Gases and water vapor can be exchanged through the leaf stomata How do plants adapt their leaf structures to deal with the climate?

11. Unit 3: Water Most water absorbed through the root hairs Wilting occurs when water loss>water uptake Life processes may slow or stop Stunting Yellowing Drop leaves Death

12. Unit 3: Water Can result in yield loss and decreased profit Water stress risk High in a germinating seed High at flowering or fruit set Pollen may not develop properly Indications of water shortage Plant will often display before damage is done Greenish-blue tint (leaves)

13. Unit 3: Water Wilting/rolling May occur only during the day and recover at night Need water, but not emergency Stays wilted through the night Immediate need for water High damage risk Reducing water loss from the soil Proper plant spacing Till soil appropriately so plants may grow to subsurface moisture

14. Unit 3: Water Avoid tillage during growth that may damage roots and open soil for moisture escape Leave lay fallow Control weeds Use mulches Early planting Sometimes, water must be supplied through irrigation What are the different types of irrigation systems?

15. Unit 3: Water Excess water Reduces availability of oxygen and carbon dioxide Can run the risk of: Diseases Root and seed rot Death Symptoms Yellowing Stunting Leaves dropping “Spongy”, slimy feeling to the plant

16. Unit 3: Water Crop selection and management should be carefully considered based on what type of soil conditions you have Crop Soil management Ridge till Raised seedbeds Planting time Other options

17. Unit 3: Water Water for Plants 500 lbs. of water/lb. dry plant material Only 5lbs. actually used in the plant Other 495lbs. lost through leaf stomata by transpiration Plants use capillary water Capillary water moves freely in the soil

18. Unit 3: Water Water sources NOT available to plants Gravity water – lost to drainage Hygroscopic water – bound to soil particles Movement of Water Translocation Transported water from roots to shoots via xylem Carries nutrients and metabolites Metabolites are products of chemical reactions or metabolized substances of the plant

19. Unit 3: Water Moves phloem to transport sugar produced from photosynthesis to all parts of the plant Roots have no other means of nourishment Water adds turgor (stiffness) to the cells Provides support to new leaves and tissue Assists w/ keeping the plant’s shape Carries transpiration Buffers temp changes Stabilizes pH in metabolism Facilitate chemical reactions

20. Unit 3: Water Maintain cellular cytoplasm Transpiration Evaporation of water from leaf and plant surfaces Last step of the water pathway Plant respiration & photosynthesis result in water and heat Transpiration cools the plant >90% of all water entering a plant is given off through this process

21. Unit 3: Water Water lost through the leaf stomata Free exchange/release of water vapor Close at night and during stress Water in the Soil Evapotranspiration Water removed from soil by soil evaporation and plant transpiration Soil evaporation can account for 20-30% of total ET

22. Unit 3: Water Soil evaporation rates are higher after rainfall and irrigation Evaporation & transpiration are driven by the atmosphere’s influence to dry the soil Just like water drawn through the plant, it’s drawn to the atmosphere High conc. ---- Low conc. ET & Crop Yield Crop yield directly related to ET Increases linearly w/ increase in ET to maximum Extra water above ET demand will not increase yield

23. Unit 3: Water Ability of plant to transpire water varies w/ climate and variety All water can’t be turned into ET and yield Factors Affecting ET Weather Power of atmosphere drives soil evap. & crop transpiration Air temp, humidity, solar radiation, wind What types of days would result in increased ET? Crop and soil may or may not be able to meet atmospheric ET demand

24. Unit 3: Water Sets the demand for crop ET Helps us to make irrigation decisions Crop type Different crops use different amounts of water during a growing season See tables 6-1 through 6-6 Why is alfalfa so high? Differences in corn, SB are due to planting dates and days to maturity

25. Unit 3: Water Crop Growth Stage ET related to leaf surface area Which would transpire more, a large plant or a small one? Maximum ET just prior to the reproductive stage Avg. max ET for corn, SB, wheat ~.3-.35”/d Crop Variety Relative maturity has most impact on seasonal ET needs Ex. 120d corn will need more water than 85d corn Difference is total water use, not daily amount used Why might this be important?

26. Unit 3: Water Crop Population What population do you plant? Do you think that ET would be higher or lower if you decreased population by 25%, 50%? What might be different w/ dryland farming? Irrigation? Surface Cover & Tillage Cover crops, mulch will help decrease ET Even as crops grow and shade the soil ET continues

27. Unit 3: Water Availability of Soil Water Relates to ability of the soil to transport water to the root zone Speculate what types of soils will have more/less trouble w/ providing the plant sufficient water Estimating ET Need weather stations to calculate temp, humidity, wind, radiation Can calculate potential ET Most important if you are irrigating Why?

28. Unit 3: Water Irrigation Water can be lost in two ways: Runoff – rainfall rate exceeds soil’s infiltration rate Deep percolation – rainfall exceeds the soil’s water holding capacity Irrigation systems Selection of a system should be matched w/: Land slope, water intake rate and holding capacity, crop water tolerance, wind

29. Unit 3: Water Flood Irrigation Used on leveled land Orchards, vineyards, hay, pasture, cereal grains Slope of.1 to.4’/100’ Water enters through a head ditch and released into the field bound by levees Furrow Irrigation Very widely used Water moves through furrows between plant rows Infiltrates the soil through capillary action Efficient, but expensive and labor intensive Very uniform crop maturation

30. Unit 3: Water Sprinkler & Drip Irrigation Pumping unit, control head, mainline and pipes, lateral pipes Emitter – very small openings (pinhole size), misting, fogging, drip, etc. Low psi (5-40) Lower flow rate (.5-15g/hr) Sprinkler – more of a spray Rotating, stationary nozzles, perforated pipe Can operate from 5-80psi depending on nozzle size

31. Unit 3: Water Discharge varies from few gpm to 1000gpm Coverage area up to 500’ Things to consider: Nozzle size, jet angle, wind, overlap, sprinkler rotation Important for determining application rates, spacing, droplet size 50-60% overlap Irrigation Efficiency Not all water sprayed reaches the ground ~15% lost to direct evaporation

32. Unit 3: Water Drip systems may lose only 10% Sprinklers may lose 25% Timing of Irrigation Water-holding capacity of soil and available plant water or keys for determining timing Must know how much water is in the bank When should irrigation begin? Determining irrigation needs Feel test Electrical conductivity

33. Unit 3: Water Moisture probe Evaporation pans Computer program Water budgets Tensiometers Climate Concerns More difficult to manage irrigation in humid regions Why? What is the difference? How would we change our irrigation strategy?

34. Unit 3: Water Arid & Semiarid Regions What dependence will we have on irrigation? What will the return be? Water use can be.25”/d

35. Unit 3: Water Unit 3 Assignment: Ch. Review questions pg. 137 Nos. 6-9, 11, 12, 14, 16 Each will be worth 2 pts for a total of 16 pts