DEPARTMENT OFPRIMARY INDUSTRIESVegetable - -Matters--of--FactsBased on research funded by the vegetable growers levy,Horticulture Australia and the Department of Primary Industries-VictoriaNumber 41October2006Managing the DroughtMain points• Ensure your irrigation system is operating at its most efficient• Minimise the evaporation of your irrigation application by watering at night or earlymorning• Decide now what you will do if water becomes restricted and which crops are mostimportant• Monitor soil moisture and irrigation outputAn efficient irrigation systemCheck your irrigation system when it isoperating and look for:• Leaks• Blocked lines• Worn sprinkler headsInstall shut-off valves to allow the pipes todrain back into storage before beingdisconnected.Run-off occurs when the application of waterexceeds how fast the soil will accept water(infiltration). This is a waste of water andmay cause erosion. If necessary reduce theapplication rate of the systemMinimize EvaporationIt is important that the water you apply is ableto get to the rootzone. Evaporation meansthat precious water is lost, but you canminimize the effects.Irrigate in low wind conditions.No point in watering headlands and roadsjust because that’s the way the wind isblowing.Use Windbreaks, nursecrops andcovercrops all help reduce evaporation andprotect established seedlings.These support crops should be slashed oncethe main crop becomes established so thatthey do not compete for water and nutrients.MulchesPlastic or organic mulches will also reduceevaporation from the soil.TimingIrrigate when temperatures are at theirlowest, at night or early in the morning. Thiswill reduce evaporation and the impact ofsalty water on crops.Measure the output of your irrigation system.Use rain gauges, buckets or tin cans. Spreadthem throughout the paddock to get anoverall picture of what the irrigation system isapplying.Check for even distribution. Check thevolume applied in an hour. Seek advice froman irrigation company if problems show up.Note: that it is important to consider thepossible disease implications of irrigating atnight. Some vegetables should not have wetleaves for long periods in certain weatherconditions because this may encouragedisease development.If in doubt seek further advice.
What if water does become restricted?Think Ahead - you may be faced with nothaving enough water to meet your needs.What you should do in these circumstancesshould be decided now while you have timeto think about it calmly, rather than in theheat of the moment.What else can you do?Monitor soil moisture levels to prevent overwatering and schedule irrigation for whenplants need it.This can be done using a range of methodsincluding tensiometers, resistance blocks,neutron probe, environscan and aqualflex toname a few.Pan evaporation will also give a good quideas it will be closely linked to how much soilmoisture will be used.Critical periods for correct irrigationCritical PeriodCropFlowering, pod setting Beans PeasHead formation and enlargement Broccoli Cabbage Cauliflower LettuceTasselling, pollination, ear fillingSweet cornFlowering, fruit set and development Cucumbers Zucchini Eggplant Peppers Tomatoes MelonsBulb formation and enlargementOnionsFernAsparagusRoot development Carrots Turnips ParsnipsContinuous Greens SpinacheTuber set and enlargementPotatoesRooting Depth of some Vegetable CropsShallow Rooted (to 30cmdepth)Celery, Lettuce, Onions, Potatoes,RadishesIs Trickle/ Drip irrigation an option for you?Drip irrigation is one of the more advancedtechniques being used today, because it is muchmore efficient than traditional spray irrigation.Trickle irrigation is rapidly gaining popularity,particularly in arid regions where water availabilityis limited. In drip irrigation, water is run throughpipes (with holes in them) either buried or lyingslightly on or above the ground next to the crops.Water slowly drips onto the crop roots and stems.Very little is lost to evaporation and the water canbe directed only to the plants that need it, cuttingback on water waste.Develop a contingency planYou will need to consider a number of things to ensure youget the maximum return from your crop.You may have to sacrifice some crops if there is not enoughwater.• Which crops are of higher value?• Are there lower value crops, which could be sacrificed forthose of higher value?• Is it important to retain markets and contracts• Are you growing any crops that are likely to be in shortsupply because of the drought – these may end up beingof high value.• Which crops are showing particularly good yields?• Which crops can stand reduced irrigation?Newly planted crops will need more frequent and lighterirrigations than mature crops, which have developed strongerroot systems.Correct irrigation is critical at certain periods of plantdevelopment. Crops in these stages should have waterallocated to them in preference to crops in non-critical stages(see table)Shallow rooted crops will require lighter more frequentirrigations than deeper rooted cropsIntermediate rooting depth (30-60cm)Broccoli, Beans, Cabbages, Carrots, Cauliflowers,Cucumbers, Peppers, Tomatoes, ZucchiniDeep rooted (> 60cm)Asparagus, Parsnips, Pumpkins,Sweet corn, WatermelonAre you on our mailing list?If you would like to receive your own copy ofVegetable Matters-of-Facts please contact theeditor: Rob Dimsey T: 03 5152 0600Check us out and view our other fact sheetson our easy to find website:http://www.dpi.vic.gov.au/vegchequeFor more information please contactyour local VegCheque officer :Neville Fernando Gippsland 5624 2267Sally-Ann Henderson Northern Vic 5051 4500Bruce Fry South West Vic 5233 5510Slobodan Vujovic Melbourne 9210 9297Elizabeth Wharton 92109222Vegetable Matters-of-Fact is published as part of DPI’s VegCheque extension program. Editor: Rob Dimsey T: 03 5152 0600Disclaimer: This publication may be of assistance to you but the state of Victoria and its employees do not guarantee that thepublication is without flaw of any kind or is wholly appropriate for your particular purpose and therefore disclaims all liability for anyerror, loss or other consequences which may arise from you relying on any information in this publication. The State of Victoria, Department of Primary Industries, 2006. ISSN: 1445-5676