Photosynthesis is one of the hallmark functions of a plant, and is a key difference between plants and animals (animals can’t photosynthesize, of course). Think about it this way: humans and animals can move around their environment to attain food and water and to escape uncomfortable or unsafe conditions. Plants can’t – they’re rooted in place and so must be able to meet all their needs using the tools they have. Photosynthesis occurs mainly in the leaves of plants, although it can occur in any part of the plant that is green. Photosynthesis happens in the chloroplasts where the green pigment, chlorophyll, absorbs light. Plants use carbon dioxide taken up from the atmosphere through leaf stomata, water taken up through the roots, and sunlight to produce sugars (also known as carbohydrates). Plants use the carbohydrates from photosynthesis to grow. Greenhouse growers can increase the rate of photosynthesis of horticultural plants by enriching the greenhouse environment with carbon dioxide. This cause plants to grow faster. We’ll take more about this later in the semester when we cover greenhouse production.
Most vegetables don’t like fluctuations in water availability
mainline, valve, sub-main, backflow preventer, pressure regulator, filter, tubing adapters and fittings, drip tubing, emitters, and end caps.
The mainline is the pipe that runs from the water source – typically your outdoor faucet - to the valve; and the sub-main runs from the valve to the point where the drip tubing is connected. Generally, sub-mains are used only when there are multiple lines of drip tubing and zones feeding off of the same mainline water source. The combined length of the mainline and sub-main should not exceed 400 feet.The valve controls water flow into the system and can be set for either automatic or manual control. Backflow preventers are necessary to ensure that irrigation water does not flow back into the pipes and contaminate your main water source. Pressure regulators are only necessary if your water pressure is over 40 pounds per square inch. If you do not know your water pressure it is a good idea to install one just in case. Filters keep dissolved substances in your water from clogging the emitters over time. Install filters either at the emitters or at the water source to protect both the valve and pressure regulator in addition to the emitters. It is best if the filter has at least a 150 mesh screen or higher. Tubing adapters and fittings are used to attach the drip tubing to the rest of the system. It is important that these are the right size for the tubing to prevent them from blowing apart under pressure.
Because small amounts of water are applied slowly, drip irrigation is designed to run daily unless it rains. How long to run the drip irrigation system will depend on how much water your plants require per day and the flow rate of your emitters. Water is applied either once or twice a day. Early morning is the best time to water because there will be less evaporation. Watering in the evening increases the plant’s susceptibility to disease.
Grow Your Own, Nevada! Spring 2013: Efficient Irrigation for the Home Vegetable Garden
Efficient Irrigation for the HomeVegetable GardenHeidi KratschState Horticulture Specialist
What we will cover…• How much water do plants need?• How does water move in your soil?• Measuring water application• Types of irrigation systems
Why do plants need water?• Plants use light +CO2 and water tomake sugar.• Sugars are used bythe plant forgrowth or stored.
Why do plants need water?• Most vegetablesare 80 to 95%water• Yield and qualitysuffer from lack ofwater
What affects water loss fromplants?•Sunlight•Temperature•Humidity•Wind
Large leaves have more poresWhat our eyes see What our eyes can‟t see
Critical water periods for vegetables• Beans – high water demand; need most criticalduring flowering and pod sizing• Corn – high water demand; peak demand duringtasseling, silking and ear formation• Leafy vegetables – water most critical duringhead development• Tomato – Water needs increase with plantgrowth; uniform watering is critical during fruitdevelopment
Critical water periods for fruits• Apples, pears, peaches, plums, cherries – duringflower formation, fruit set and final fruit swell• Raspberries and blackberries – during bloomand during sizing of fruits• Strawberries – at planting, during runnerformation and during flower bud development
There are two aspects to watering• How much to applyat one time…• How often to applyit.
How to water your plants• Applying too muchwater at one timeleaches nutrients fromthe soil.• Applying water toooften suffocates roots.Flooding plants deprives roots of oxygen
How much do I water?• Sandy soils need watermore frequently.• Water more frequently inhot weather.• New seedlings ortransplants need morefrequent watering.• Large, deep-rooted plantsneed deeper watering.
How much water to provide…• 1 to 2 inches perweek during hotweather• Depends on:▫ air temperature▫ size of plant▫ Stage ofdevelopment
Measuring sprinkler irrigation amountCatch-can test:• Scatter soup cans around the garden• Turn on irrigation• Measure amount of water in cans after 15 minutesof irrigation
Measuring your irrigation amount• Say you measure ¼inch after 15 minutes• Assume garden needs1.5 inches water perweek• You might water for15 minutes 6 timesper week, or for 30minutes 3 times perweek
How often to provide water• Rate of evaporation• Rate of movement insoil• Affected by soiltexture
CLAYSILTSANDWater movement through different soil types0123Depth (Feet)
Affect of soil texture on water-holdingSandy soil Clay soil• Each foot of soildepth holds about ¾inch of availablewater• Each foot of soildepth holds about 2to 2-1/2 inchesavailable waterClay soils have a greater water-holding capacity than sandy soils.
Get your hands in the soil!• Dig down 2 to 4inches in the soil• Soil near fieldcapacity will feelmoist but not wet• Plants mayexperience droughtwhen the soil feels dryand crumbly
Indicator plants• Squash Cucurbitahybrids• Tomato Lycopersiconhybrids• Wilting leaves and/orstems• (May also happen inlate afternoon sun –they will recover)
What’s wrong with my plant?Diagnostic ChartCAUSE OverwateringUnderwateringNutrientdeficiencySOILCONDITIONWet Dry Wet or dryLEAFCONDITIONYellow,fallingoffWilted,curled,tip burnYellow, butremains onplant
Water problems• Blossom end rot occurs onblossom end of fruits• Caused by calcium not gettingup to fruits• The problem is inconsistentwatering• Apply mulch to hold water inthe soil• Do NOT apply lime or gypsum. Water fluctuations can also causefruit cracking.Blossom end rot
Watering methodsSprinkler irrigation• Automatic• Less efficient due to:▫ Wind▫ Evaporation▫ Weeds
Watering methodsHand watering• Time consuming• Generally only wetsupper layer of soil• Are you providingconsistent amounts toeach plant?
Watering methodsSoaker hose• Easy• Inexpensive• Saves water• Hoses must bereplaced often• Best in a flat areawith rows not longerthan 25 feet
External emitter staked on a riserAttach an externalemitter to the endof ¼-inch feederline and stake witha riser to mistplants.
Ends must be capped or clamped tomaintain water pressure.Hose end clampHose end cap
Some EASY math… The maximumpressure handled by adrip irrigation systemis 25-40 psi (poundsper square inch).If in doubt, install apressure regulator:• The total gph flowingthrough emittersshould not exceed75% the total flowrate of the driptubing:▫ Number of emitters ×GPH per emitter = totalGPH through emitters▫ Example: 300 1-GPHemitters can besupported by systemwith a 400 GPH flowrate.
To measure flow rate for drip:• Get a 5-gal. bucketand a stop watch.• Put bucket under thefaucet.• Turn on faucet andstart timer.• Calculate how long ittakes to fill thebucket.• 5 gal / (45) seconds ×3600 sec/hr = (400)GPH flow rate.
Plastic mulch• Black polyethyleneplastic film for dryclimates with coolsprings• Drip irrigation laidunder the plastic• Controls weeds• Warms the soil for anearlier crop
Subsurface drip systems• Uses buried drip tubing – 6to 24 inches deep• Saves water and improvesyields• Higher initial investment• Good for hot and windyareas• Efficiency depends on“wickability” of soil• Not good for quick-drainingsandy or gravelly soils• (Great!) potential for rodentdamage
Gravity drip bucket systems• Buckets need to beelevated at least 3feet from the ground• Use with dripirrigation tape• Fill buckets oncedaily• Use where wateravailability islimited
Watering from a well system• Backflow protection• Determine steady stateflow rate and pressure.• Insert a delay betweenstations that allows thewell to recharge.
Septic systems: can I plant on or nearmy leach field?• No! Do not site your vegetablegarden (including fruit trees)over the leach field.• Roots may damage the leachfield.• Crops may be contaminated withbacteria or viruses.• Root crops (carrots, potatoes)may be directly exposed tohuman pathogens.• Fruits and vegetables should beplanted at least 10 feet from aseptic system or leach field toavoid bacterial contamination.
Artichokes• Grow from transplants orseed (transplant 3-4weeks before FF date).• Requires cool temps toinitiate a flower stalk.• Drip irrigation is best;keep soil moist; roots areshallow.Artichokes are flower buds.„Green Globe‟ heirloom
Beans and peas• Water:▫ Keep soils moist butnot wet.▫ Water most criticalduring flower andpod development.▫ Dry beans: reducewater as seeds beginto mature„Blue Lake‟ – pole typeLack of flower development or“stringy” beans indicate water orheat stress.
Beets• Grow from seed.• Water regularlyusing drip irrigationto keep soil moist.• Moisture fluctuationscause root cracking.• Weed control isessential!„Detroit Dark Red‟Heat and water stress maycause woody beets.
CarrotsWater▫ Use drip irrigationif possible.▫ Avoid over-watering to preventhairy roots andforking.„Imperator‟Uneven watering causes root cracking.
Broccoli• Best grown astransplants.• Water:▫ Deeply andinfrequently toencourage deep roots.▫ Use mulch to conservewater and controlweeds.„Calabrese‟ heirloom“Buttoning” (premature flower buds)soon after transplant can be causedby water stress.
Brussels sprouts• Grow from seedstarted indoors.• Water:▫ Deeply andinfrequently toencourage deeproots.▫ Use drip to provideeven moisture. Usemulch.„Long Island Improved‟Uneven watering promotessplitting, bitter taste and tipburn.
Cabbage/brussels sprout tip burn• Calcium not transportedto rapidly expandingtissues.• Common in sandy soils.• Caused by any conditionthat favors rapid growth.• Maintain even moisturelevels. Tip burn on brussels sprout
Leeks• Water:▫ Roots are shallow;provide waterregularly.„American Flag‟Weed control is especiallyimportant during the first 2months of growth.
Cucumbers• Love sandy soils andlots of room!• Water deeply by dripor basins• Over- and under-watering causes:▫ Bitter fruits▫ Pointed ends▫ Misshapen„Marketmore‟Cucumber plants are vining and benefit from a trellis.
Potato• Grown from “seedpieces”• Soils must be 50 F• “Hill” soil aroundplants as they grow toprevent tuber“greening.”• Water:▫ Deep, regular wateringwith drip irrigation.▫ Reduce water as leavesyellowIrregular soil moisturecauses abnormal tubergrowth.Many potato varietieswill grow in northernNevada.