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IrriGate Newsletter, Issue Spring 2011 - Issue 7

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Sustainable Irrigated Landscapes - North East - Mid and Upper Goulburn Broken

Logo showing the North East area in relation to VictoriaLogo showing the Upper Goulburn Broken area in relation to Victoria
North East Dryland CatchmentGoulburn Broken Dryland Catchment (excluding the Shepparton Irrigation Region)

Welcome to IrriGate Issue 7

It is getting close, or may have already past, time to consider the first irrigation to avoid production losses. Dig up some dirt and make an assessment, and remember there is still grant money available for soil moisture monitoring tools. I would also like to thank Wendy Paglia for her help over many years and welcome Suzanne Briggs to the team.

Dennis Watson - Editor


Inside this issue

Counting the cost of poor distribution uniformity | Seeking interest in Tracking irrigation | NE/GB Sustainable Irrigation Team - Dryland


Counting the cost of poor distribution uniformity

The distribution uniformity of a spray irrigation is a measure of how efficiently water is applied across the paddock. This is measured as a percentage the higher the better. A low distribution uniformity can mean crop growth is reduced, or more irrigation water needs to be applied to compensate. As well as using more water this also increases pumping costs.

An average water demand for most fodder crops and pastures in the North East and Goulburn Broken Dryland CMA regions is around 6 ML/ha. Compensating for a poor distribution uniformity of 70% and applying more water to make it equivalent to a 90% system means applying an extra 1.9 ML/ha. The extra cost of this water and pumping is likely to be around $60 to $150 per hectare depending on the irrigation system and the power source. For high yielding viticulture the average demand is around 4ML/ha, which means applying an extra 1.3 ML/ha to compensate for a distribution uniformity of only 70%; costing around $60 to $95/ha. The difference between four typical irrigation system used across the regions is shown in Table 1.

extra water cost ($/ha)
extra fuel cost ($/ha)
Total ($/ha)
Centre Pivotelectricity
38
24
62
diesel
38
42
80
Bike shiftelectricity
38
46
84
diesel
38
74
112
travelling gunelectricity
38
70
108
diesel
38
114
152
Drip irrigationelectricity
26
35
61
diesel
26
68
94
Table 1: Cost of applying extra water to make up for a poor distribution uniformity

Assumptions:
  • Diesel at $1.2/litre
  • Electricity at $0.17 /Kwatt.hr
  • Water at $20/ML (temporary water value)
  • 70% pump efficiency
  • Operating at typically average pump pressures.
DPI currently can measure your irrigation systems distribution uniformity free of charge. If you are interest in more information contact Dennis Watson on (02) 6030 4567 or 0429 304 567


Seeking interest in Tracking irrigation again this season

Over the last irrigation season some irrigators took part in a program where they recorded their irrigation and rainfall. This information was examined each month to check whether irrigation application rates where keeping up with crop demands or if too much water was applied. An example from last year is sown in Figure 1. The horizontal blue dotted line represents a full soil water profile, while the horizontal red dotted line represents plant stress levels. The black line represents the theoretical plant use or soil moisture level, responding to rainfall, irrigation and evaporation. When this line drops past the red line the crop is theoretically suffering from moisture stress.

Tracking the soil moisture level over the 2010/2011 irrigation season
Figure 1: Tracking the soil moisture level over the 2010/2011 irrigation season

In this case there where a couple of times where an irrigation may have been warranted prior to December but subsequent rainfalls occurred before any major crop stress would have occurred. The crop started to enter a stressed stage late December to early January and a serries of irrigations of 11mm occurred but these where only enough to keep up with evaporation and not enough to lift the crop out of the stressed stage. The crop was then saved by some reasonable rainfall events early February. A similar scenario occurred towards the end of January. The crop was also again placed under stress for the March April period, however this may have been a deliberate method to avoid waterlogging overwinter. All up from March to February the crop could have been under moisture stress for over 70 days. Soil moisture probes were installed under the crop which validated these results.

If anyone is interested in participating in this program over the coming irrigation season please contact Dennis Watson on (02) 6030 4567 or 0429 304 567


DPI NE/GB Sustainable Irrigation Team - Dryland

Dennis Watson

Irrigation Specialist
DPI Rutherglen Centre
(02) 6030 4567
0429 304 567

dennis.watson@dpi.vic.gov.au
Dennis Watson
Dennis Watson

Suzanne Briggs

Catchment Management Officer
DPI Wangaratta Centre
(03) 5723 8674
0400 884 813

suzanne.briggs@dpi.vic.gov.au
Photograph of Suzanne Briggs
Suzanne Briggs








Welcome to IrriGate Issue 6.

I would like to take this opportunity to say farewell, I will be relocating to DPI Wangaratta to take up a new position. I have enjoyed my time with irrigation immensely, meeting and getting to know you all, originally with Water for Growth and Project Leader John Nieuwenhius and in recent times with Water Smart Farms and Project Leader Dennis Watson.

Best Wishes Wendy Paglia - Editor


Tracking water requirement over the season | Monitoring the plant’s moisture not the soils | Contact Us


Tracking water requirement over the season

What an unusual irrigation season this one has been. The majority of irrigators across the region only irrigated 2 to 3 times over the season; some not at all. Figure 1 shows an example of a theoretical water budget for lucerne grown in the Myrtleford area over the 2010/2011 irrigation season. The blue line indicates a water filled soil profile, while below the red line indicates plant stress. In this case only two irrigation events occurred, 15 mm applied on the 5 January and 25 mm applied on the 28 January indicated on the graph by the light blue triangles. This with the addition of rainfall was enough to just about keep the water balance out of a negative state, until the start of March. Another irrigation at this point in hind sight could have been useful. However given the rainfall events prior, at the time it made sense not to irrigate and exacerbate potential water logging issues as winter approaches.

Figure 1: Water balance of lucerne over the 2010-2011 irrigation season
Figure 1: Water balance of lucerne over the 2010-2011 irrigation season

The yellow dots on the graph are soil moisture readings shown in Kpa using the scale on the right hand side of the graph. These were recorded from a “G-dot” installed at 30 cm. The soil moisture readings correlate pretty well with the theoretical water balance.

i.e. when the theoretical water balance is indicating the soil moisture is adequate the probe is saying the same thing, and when the water balance is getting dry the probe reflects this.


Monitoring the plant’s moisture not the soils

A number of irrigators are striving to improve water use efficiency by measuring the level of moisture stored in the soil to determine if irrigation should occur and how much water should be applied. There is a myriad of equipment out there that can help do this. There is however other equipment which can measure moisture stress directly from the plant. There are a couple of benefits of doing this.

  • The reading is a direct measure of how the plants are feeling, not an assumption based on soil moisture levels.
  • The other benefit is determining if there are plant health problems. For instance the soil moisture may be adequate but there may be root constraints such as root-rot problems, or soil compaction, soil acidity, or the root system may be reduced due to poor past irrigation practice to name a few.
One such piece of equipment is the “Pump-Up Pressure Chamber” (Figure 2). This works by placing a leaf in a chamber and applying pressure until moisture droplets starts to appear (viewed through a microscope) on the cut leaf stem (Figure 3). The higher the pressure required to produce the droplets the higher the moisture stress of the plants.

This can be a little bit awkward and time consuming to use in the field on a daily basis but can provide some very useful information at strategic times throughout the irrigation season. The “Pump-Up Pressure Chamber” is more commonly used in horticulture than the fodder industry.

This units sell for approximately $1,500, but remember you may be eligible for a 50% rebate.

More information can be found on the following website. www.pmsinstrument.com (external link)
Figure 2: Pump-Up Pressure Chamber
Figure 2: Pump-Up Pressure Chamber


Figure 3: Diagram a leaf in the Pump-Up Pressure Chamber
Figure 3: Diagram a leaf in the Pump-Up Pressure Chamber



Wendy Paglia

Project Support Officer
DPI Ovens Centre
(03) 5731 1206

wendy.paglia@dpi.vic.gov.au
Wendy Paglia
Wendy Paglia


If you would like to receive this information/publication in an accessible format (such as large print or audio) please call the Customer Service Centre on: 136 186, TTY: 1800 122 969, or email customer.service@dpi.vic.gov.au

Published by the Department of Primary Industries, Sustainable Irrigated Landscapes, March 2011,

The State of Victoria, 2011

This publication is copyright. No part may be reproduced by any process except in accordance with the provisions of the Copyright Act 1968.

Authorised by the Victorian Government, 1 Spring Street, Melbourne 3000

ISSN :1837-4077

Disclaimer:
This publication may be of assistance to you but the State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.

For more information about DPI go to www.dpi.vic.gov.au or call the Customer Call Centre on 136 186.
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