Irrigation futures - irrigation in vegetables, technology and practice


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Irrigation in vegetables: technology and practice

This article was written by Evan Christen, Jim Ayars, John Hornbuckle, and Mark Hickey. It was published in the Irrigation Australia Journal in Winter 2008, Volume 23 No. 2. It is an extract from “Technology and practice for irrigation in vegetables” published by the NSW Department of Primary Industries.

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Irrigation futures - irrigation in vegetables, technology and practice

  1. 1. CRCIFCRCIFIRRIGATION IN VEGETABLES: TECHNOLOGY AND PRACTICEEvan Christen, CSIRO Land and Water, Griffith, NSW; Jim Ayars, CRC for Irrigation Futures;John Hornbuckle, USDA-ARS, California; and Mark Hickey, NSW DPI, Yanco, NSWIt is important to identify the bestirrigation practices that will allow thevegetable industry to develop intothe future. To help achieve this, thesuitability and risks associated withdifferent irrigation systems havebeen broadly ranked in the areas ofwater quality, environmentalmanagement and agronomic factors. In general terms irrigation systemswith better water control(drip/sprinkler) are more likely to besustainable and reduce the risks ofnegative environmental impacts. Forpathogen control, the use of dripirrigation and ultimately buried dripirrigation is clear advantageous. Dripirrigation does have some specificproblems if there are high suspendedsolids in the water and if there is aneed to germinate seeds. Sprinklerirrigation is very useful if dust controland cooling are required. A recent project has helped describe the best practices for irrigating vegetables by identifying the suitability and risks associated with different irrigation systems and rankingMatching crops, soils, water, quality them in the areas of water quality, environmental management and agronomic factors.and irrigation methodsThere can be no definitive answer asto which type of irrigation system is quality parameters, likelihood of based on the criteria have beenmost suitable for vegetable minimising environmental described as high (H), medium (M),irrigation as there are so many problems, and appropriateness for and low (L).variables. In the following tables we efficient and economic crop To help achieve this, the suitabilityhave rank the three main irrigation production. The irrigation systems and risks associated with differentsystems against the key criteria are broadly assessed against these irrigation systems have been broadlyrelated to irrigation for vegetables. criteria below. ranked in the areas of water quality,The main areas of assessment for The potential for using a particular environmental management andirrigation systems are against water system or risk associated with a system agronomic factors.Table 1. Water salinity and irrigation system suitability*. All irrigation carries Salinity Drip Sprinkler Furrow potential risks to the Buried Surface Fixed, Traveller environment. These risks centre pivot are exacerbated if reclaimed Low H H H H M waters are used, due to Moderate H H M** M M potentially high levels of High M M L L L salts and nutrients. Apart from soil salinity, the other* Assuming all soils have reasonable drainage; if drainage is very poor, then drip should be used. main factors are surface** Leaf burn becomes a problem. run-off and deep percolation. IRRIGATION AUSTRALIA 19
  2. 2. CRCIF Water quality Table 2. Pathogens, aerosols and risk of contamination. Salinity. Managing soil salinity will Salinity Drip Sprinkler Furrow be key to irrigation sustainability. Irrigation systems with better water Buried Surface Fixed, Traveller control are inherently better suited centre pivot to managing salinity. Table 1 refers to the management of soil salinity, Ingestion risk L M M H M but leaf burn with sprinkler Contact risk L H H H H irrigation may also be a problem when using saline waters. Aerosol risk L L H H L Pathogens and aerosols. Where reclaimed water is used for Table 3. Clogging, precipitation and corrosion risk, and irrigation system suitability. vegetable production, risk of Water quality factor Drip Sprinkler Furrow pathogens contaminating the Fixed, product is one of the key Buried Surface Centre pivot limitations. The risk of contamination varies according to High suspended solids L L M H the crop and irrigation system used. High potential precipitates L L M H Production and drift of aerosols is also an issue (Table 2). High biological activity L L M H Clogging, precipitation and pH <6, >9 L L L M corrosion factors. Depending on the water source, there are varying Table 4. Risk of surface run-off with irrigation system and soil type. risks of clogging, precipitation and corrosion affecting the operation Soil type Drip Sprinkler Furrow and longevity of an irrigation system. Generally, furrow irrigation Buried Surface Fixed, Traveller is least susceptible to these centre pivot problems (Table 3). Sand L L L M L Environmental management Loam L L M H M All irrigation carries potential risks Clay L L H H H to the environment. These risks are exacerbated if reclaimed waters are Table 5. Deep percolation risk with irrigation system and soil type used, due to potentially high levels of salts and nutrients. Apart from Soil type Drip Sprinkler Furrow soil salinity, the other main factors are surface run-off and deep Buried Surface Fixed, Traveller percolation. The risks of these centre pivot occurring with different systems are Sand M M H H H outlined below. Surface run off. Surface run off in Loam L L L H H irrigated agriculture is caused by Clay L L L M M applying more irrigation water than can infiltrate into the soil, as well as Table 6. Soil type and system suitability for crop production. by rainfall. This can be a limiting factor to irrigation in some regions. Soil type Drip Sprinkler Furrow Systems with good control of application rate and amount and Buried Surface Fixed, Traveller with high uniformity have lower centre pivot likelihood of run off. Systems with Sand L M H M L high application rates, such as travellers, make it hard to control Loam H H M M H surface run off and excess drainage Clay M M L L M into low areas of the crop. Systems that leave parts of the soil surface Table 7. System suitability for crop establishment. dry reduce the risk of run off due to rainfall (Table 4). Type of crop Drip Sprinkler Furrow Deep percolation. Deep percolation of irrigation water down past the Buried Surface Fixed, Traveller root zone is the other main loss of centre pivot water. Good irrigation management Small seeded crops L M H L M and scheduling are the keys to minimising deep percolation. Deep Large seeded crops L H H M H drainage can be much higher with Transplants or cuttings H H M M M furrow irrigation than when using20 IRRIGATION AUSTRALIA
  3. 3. CRCIFdrip or sprinkler irrigation, mainly Table 8. Irrigation system and disease risk.due to less uniform application thanwith these systems. The risk of deep Crop type Drip Sprinkler Furrowpercolation on very sandy soils is Buried Surface Fixed, Travellerhigh with all types of irrigation centre pivotmethod. Even with the best irrigationmanagement, rainfall can cause Large surface area crops L H H M Mconsiderable deep percolation, soirrigation is not recommended on Root crops L M M M Msandy soils (Table 5). Cucurbits, tomatoes etc L H H H MAgronomic factors Trees, vines, cane, fruit L H M M MSoil–water properties. For good crop Table 9. Irrigation system and dust control/cooling.production there needs to be anappropriate match between the soil Control levelphysical properties controlling watermovement and retention and the Control factor Drip Sprinkler Furrowirrigation system. This affects theamount of water that can be stored Buried Surface Fixed, Traveller centre pivotin the soil after an irrigation, thedepth of wetting, wetting pattern Soil/sand blowing L L H H Mand aeration status. These factorsaffect the ease of management and Dust control L L H H Magronomic productivity of the land Cooling L L H H M(Table 6).Crop establishment. Establishment Table 10. Irrigation system and weed control.of crops is a critical task inhorticulture; the irrigation system Control levelmust be able to do this with a highdegree of success. Table 6 is suitable Weed control Drip* Sprinkler Furrowfor this assessment, except when Buried Surface Fixed, Travellerconsidering a buried drip system, in centre pivotwhich case it is very difficult toachieve good seed germination in Travellerany soil type. Table 7 outlinesirrigation system suitability for At germination H H L L Lestablishing various categories of Mid – late season H H L L Mplant material.Disease. Control of leaf and root *If using pre-emergent herbicides that require watering in, drip irrigation is generally unsuitable.diseases, especially fungal diseases, isaffected by the irrigation system,crop and soil type. In general, waterlogging. Broad assessments of surface. Drip in combination withsprinkler systems increase risk of leaf irrigation systems and potential for plastic polythene mulch or the use offungal and bacterial infections, disease are given below (Table 8). transplants can be particularlywhereas furrow irrigation increases Dust control and cooling. Control of effective for controlling weeds.the risks of root rots due to dust is important for some vegetable It is important to note that certain production, to keep the crop clean. It pre-emergent vegetable herbicides is also important that the harvested require ‘fixing’ into the soil with 10 product is dust free. In the same to 15 mm of overhead irrigation to be category is the task of cooling, which most effective. This could preclude is required for some crops. Sprinkler the use of drip if alternative irrigation provides the best potential herbicides cannot be used. for controlling these factors as it wets A broad assessment of irrigation the entire surface area. A broad assessment of irrigation system system potential for these factors is To reach the decision-makers in the potential for these factors is given in given in Table 10. irrigation field, you should consider Table 9. This article is an extract from advertising in Irrigation Australia “Technology and practice for irrigation in Weed control. With vegetable Journal, the official journal of Irrigation vegetables” published by the NSW production, minimal competition is a Australia. high priority, and the weed control Department of Primary Industries. The that can be achieved by different full report is available on the NSW DPI For information on advertising rates, website at systems is important. Drip systems please contact Brian Rault at Hallmark offer the best potential, as they wet Editions, Tel (03) 8534 5000 or email little of the soil. Buried drip systems pdf_file/0005/201101/Technology-and- are even better, as they can be practice-for-irrigation-in-vegetables. managed so as not to wet the soil pdf. IRRIGATION AUSTRALIA 21