Fruitcheque Drought Strategy Checklist

Whole Farm Planning

Information on Whole Farm Planning can be found by contacting your Local TAFE, Department of Primary Industries (DPI) office and/or local Landcare Group/Landcare Coordinator. Courses can be found by visiting Short Courses Victoria (external link).

Landcare Coordinators or Landcare Groups would be another good contact point as they may know of local courses or events being conducted.

The nearest Landcare coordinator can be contacted through your Catchment Management Authority (external link). In some areas the CMA through their community education programs might run courses/events.

Some DPI regions have designated Whole Farm Planning Officers who run courses. Some DPI regions, in conjunction with local Landcare Groups, run single day Whole Farm Planning events. That may be another option to pursue to know more about Whole Farm Planning.

Details about the Victorian Whole Farm Planning Network can be supplied by the DPI Customer Service Centre by calling 136 186.

(Source: Customer Service Centre, FAQ)

Information about caluculating paddock areas can be found via Target 10 (external link).

Visit the Farm Gross Margins page.

You may also like to use the stone fruit water budgeting tool spreadsheet.

You will need to consult with whom you normally supply to answer this question. Do this early, so you have time to consider all avaialable options and information before making important decisions.

You will need to consult with whom you normally supply to answer this question. Do this early, so you have time to consider all avaliable options and information before making important decisions.

Its unlikely there will be a profitable market for smaller fruit.

You will need to consult with whom you normally supply to answer this question. Do this early, so you have time to consider all avaialable options and information before making important decisions. You may also need to consult with a free Rural Financial Counselling Service (external link).

Visit the Farm Gross Margins page, or talk to one of the FruitCheque team.

Watch out for the release of the Hortigator (Horticultural Budgeting Tool)

Reducing Canopy Size

Stone fruit trees of various ages in a Woorinen orchard.

There are a number of ways to control the size of your tree's which could be undertaken, even in normal seasons. Drought conditions may encourage you to consider undertaking summer pruning and RDI. The latter has already been covered quite extensively on this website, so this article will concentrate on summer pruning.

In general the most efficient way to reduce vegatitive growth on fruit trees is by careful irrigation management. However there are a number of reasons you could experiance excessive vegitative growth in the form of rapidly growing water shoots.

A light or crop will encourage the tree to grow vegatively. You may have had small fruit last year as a result of dry sub-soils and interows under trickle irrigation. That scenario will undoubtadbly encourage you to thin harder this year to maintain size. If there is not a corresponding change in water management or summer rains are experianced trees will grow with excessive vigour. Like wise, if you have removed fruit alltogether to maintian trees until the end of the drought, careful management of vegetation and soil moisture managment will be needed.

Apples:
Summer pruning can be used to reduce excess vegetative growth caused by fruit removal on apples. Care must be taken not to cause further stress by excessive pruning. The timing of summer pruning is important. It is better to wait until the terminal shoots have stopped growing before you prune.

(Source: Julie Brien, District Horticulturist, NSW Agriculture, Tumut)

Stonefruit
There is a direct link between canopy size and tree water use. Although, radical removal of limbs (Eg. reducing the number of leaders/tree) should only be attempted after fully considering the implications to future yeilds. Removing entire limbs will effect yeild for a number of years. Other losses in effiency may also be experianced while the tree structure is regianed.

Summer pruning is the action of removing shoots from the interior, shortening spurs and a general shaping of the tree for maximum light interception. Summer pruning is recomeded as best management practice. The effect of summer pruning on tree water use are untested and according to a Department of Primary Industries scientist probably negliable.

Less radical machine pruning to reduce tree hieght by up to 30cm could be undertaken during the dormant period. How ever any reduction in tree size will spur the tree into growing more vegetation. Therefore a corresponding water management regime must be carried out. That regime will involve careful monitoring of soil moisture and RDI.

(Source: DPI)

Citrus
Tree water use is directly related to canopy size, so reducing the canopy reduces water use. Figure 3 illustrates the impact of canopy size on monthly irrigation applications to navel orange trees. The amount of tree canopy you remove for each block should be based on tree age, crop load, stage of growth, long-term block viability and how much water needs to be saved. Providing trees are given sufficient levels of water and nutrients they should recover to form a vigorous canopy that produces good quality fruit.

Skeletonising: Skeletonising is the most severe form of canopy reduction, involving the removal of nearly all tree branches and foliage. This type of pruning is normally used to rejuvenate old trees. Trees that have been skeletonised will use a lot less water, but can take between 2-3 years to come back into full production.
Hedging: The best time to hedge trees is in late winter/early spring to reduce the risk of sunburn to the newly exposed limbs. A light hedging will not significantly impact on next season’s production, however a medium or heavy hedging can result in trees being out of production for 1-2 seasons. One option is to hedge only one side of the tree to reduce the impact on yield.
Pruning for regrafting: Cutting back trees for grafting will also reduce water use.

(Source: Managing citrus orchards with less water (external link), Steven Falivene, District Horticulturist, Intensive Industries Development, Dareton)

Further information can be found in the article Drought Strategies and Fertilisers in Orchards or the Information Note AG0240: Efficient Fertiliser Application in Orchards

Regulated Deficit Irrigation

With RDI, trees are kept short of water when fruit growth is slow or after harvest but are given ample water during the time of rapid growth of fruit. This reduces the growth of shoots. If RDI is properly managed, there is no reduction in the size of fruit or yield; in fact, both may increase - such results have been achieved. The reason why the above technique works relates to the growth pattern of shoots and fruit. On most deciduous fruit trees, the shoots grow rapidly early in the season, and their growth slows down as the fruit begins to grow rapidly. In contrast, early in the season the fruit grows slowly. Water stress at this time will reduce the growth of shoots without markedly affecting the growth of fruit.

With RDI, the irrigation season can be divided into four periods. The duration of these periods is determined by both weather and the relationship between vegetative growth and the growth of fruit.

Period 1
In this period, the trees are not irrigated, which allows the soil to dry out. With most crops this period follows flowering, however, with peaches there is initial rapid fruit growth following flowering when water stress must be avoided. In the Goulburn Valley trees are not irrigated until evaporation exceeds rainfall by 100 mm. If low rainfall during winter and early spring occurs or in environments dissimilar from the Goulburn Valley (for example, trees growing in lighter or deeper soil types), soil moisture must be measured. Irrigation should commence when the soil has dried out to 100 kPa in a sand or 400 kPa in a clay loam. In the Goulburn Valley this could be as late as mid-November in a wet spring or late October in a dry spring.

Period 2
Once irrigation commences, the trees are watered, but with greatly reduced volumes of water compared to that which would normally be applied. Irrigation replacements of pan evaporation of less than 30% are recommended. Period 2 commences at the initial irrigation and continues until six weeks before harvest for early-maturing fruits (that is, before mid-January), and eight weeks before harvest for later maturing fruits. Soil moisture in the middle of the wetted fibrous root zone should not exceed 100 kPa in sand or 400 kPa in clay loams.

Period 3 (from the end of period 2 until harvest)
In this period, the fruit is growing rapidly and the tree now needs ample water to maintain this growth. Water stress must not occur during this final period of fruit growth. Irrigation replacements of pan evaporation of 80 to 100% are recommended. Soil moisture in the middle of the wetted fibrous root zone should not exceed 40 kPa in sand or 60 kPa in clay loams.

Period 4 (post harvest)
After harvest a similar strategy as during period 2 can be implemented. In early maturing varieties and species (for example, cherries and apricots) there is considerable shoot growth after harvest which should be kept in check to maintain fruitfulness and even cropping within the canopy. Irrigation replacements of pan evaporation of less than 30% are recommended. Soil moisture in the middle of the wetted fibrous root zone should not exceed 100 kPa in sand or 400 kPa in clay loams.

(Source: Information Note AG0299: Irrigation scheduling for regulated deficit irrigation (RDI).

Thinning

Apples
Thoroughly and aggressively apply blossom and post-flowering thinning sprays to reduce competition between fruit as soon as possible even though there is a frost risk. This is especially needed if flowering and weather conditions are conducive to high fruit set.

Decide if more thinning is needed at 6 weeks after fruit set and complete the thinning as soon as possible. Secateur thinning can be done in the top third of the tree (vase shaped trees) to speed up thinning until late October.

Choices
Choose to irrigate at a deficit and suffer a fruit size loss. Applying a mild RDI early in the season (mid November and December and again 2 weeks before harvest) will reduce fruit size. In this case heavier and earlier thinning than normal plus RDI will result in lighter crops but similar fruit size compared to a full irrigation program.

Choose not to irrigate. Lower productivity blocks could be de-blossomed or even pollarded (main limbs cut in half or pruned even lower) to reduce water needs. Wound dressing must be applied to these larger pruning cuts. Alternatively, some older trees may be close to being non-viable. This may be a good time to pull them out earlier than planned and transfer the water to productive blocks of trees to ensure some commercially viable fruit can be harvested.

Stone fruit

The stone fruit trees that orchardists have decided to take through to harvest this season need a strong commitment to a thinning program in order to produce saleable, commercial sized fruit when picked.
Last season in all irrigated fruit growing districts, orchardists experienced some problems with fruit size.
In most cases the problem stemmed from what seemed like an average crop early in the season, suffered size losses in last seasons extremely difficult dry season with limited irrigation water allocation.
This problem still looms as a possibility this season, given the early indicators of low water allocations so far and low expectations for rainfall.
Stone fruit trees in the Murray and Goulburn Valleys experienced different stress levels during the growing season last year and will need careful assessment of how much thinning is required this season.
This applies to both canning and market fruit.

The stone fruit trees that orchardists have decided to take through to harvest this season need a strong commitment to a thinning program in order to produce saleable, commercial sized fruit when picked.
Last season in all irrigated fruit growing districts, orchardists experienced some problems with fruit size.
In most cases the problem stemmed from what seemed like an average crop early in the season, suffered size losses in last seasons extremely difficult dry season with limited irrigation water allocation.
This problem still looms as a possibility this season, given the early indicators of low water allocations so far and low expectations for rainfall.
Stone fruit trees in the Murray and Goulburn Valleys experienced different stress levels during the growing season last year and will need careful assessment of how much thinning is required this season.
This applies to both canning and market fruit.

The ‘Golden Rules’ for thinning stone fruit trees are -

Thin early
Thin the earliest maturing varieties first.
Do it right the first time and thin hard enough and focus on what is left on the tree, not what is on the ground.
Supervise the job

Trees with good budwood development last season can easily over-crop, as fruit set during the warm and dry conditions so far are likely to be high. However, trees with poorer budwood can also set a heavy crop but will have lower stored nutrients in the tree from last season; therefore these trees will need accurate assessment and probably thinned more heavily than normal to ensure fruit achieves commercial size and quality.
Secateur thinning by cutting abundantly set laterals in half, is also possible for a quick initial thinning if done by mid October. Hand thinning may then still be needed to space fruit evenly along the remaining lateral.
The risks associated with early thinning are that split stones in fruit may increase and it makes larger fruit more susceptible to cracking close to harvest. However, delayed thinning may result in smaller fruit, especially for early maturing varieties.
Another risk of early thinning is the crop can be lost due to frost damage after being thinned. This results in loss of fruit for packing as well as having spent money on the labour intensive job of thinning.
It seems sensible to use fruit thinning as an offset insurance to obtaining large to average fruit size in a difficult season compared to an average to poor fruit size. This is in a market where fruit size, despite the season, is a key driver of profitable returns.

Canning as well as market peaches and nectarines will need careful and thorough early thinning to ensure commercial grade fruit

Thinning may need to be harder this season if water allocations remain low. Average to large fruit should be the aim.

Water Needs for Stone Fruit

Stage 1 - Budburst and flowering to beginning of rapid shoot growth.
Tree water needs increase as cell division occurs and the canopy starts to develop. At the end of this stage you will a Crop Factor of 0.6. Tensiometer readings should be kept between 8 and 40 kPa.

Stage 2 - Beginning of rapid shoot growth to beginning of fruit fill.
Fruit growth is slow, shoot growth is fast and water use is stable. Crop factors generally maintained at 0.6.
Tensiometers should still be kept between 8 and 40 kPa. If using RDI the crop factor can be less, perhaps 0.3 and soil moisture can be allowed to dry to 200 kPa.
Recommended soil moisture levels of peach, at different growth stages.
Recommended soil moisture levels of peach, at different growth stages.

Stage 3 - Beginning of fruit fill to harvest (4 - 8 weeks).
Fruit growth is rapid and needs large amounts of water to reach its potential size. Fruit still has the same number of cells that have to be filled to enlarge the fruit. The tree will hurriedly need more water. Crop factors need to increase to 1 - 1.2 and soil moisture should be showing as 8 - 40 kPa on the Tensiometers.

Stage 4 - harvest to leaf fall
when fruit is harvested water requirements drops dramatically and the weather may result in less losses from evaporation. However, water is still needed to maintain healthy leaves. the crop factor will be around 0.4 and the soil could be allowed to dry to 200 kPa.

Stage 5 - Leaf fall to Budburst and flowering.
The trees no longer need irrigation as they have entered the dormant phase. Soil moisture monitoring will need to commence in spring to determine when to apply the first irrigation.

(Source: Guide to best practice water management - orchard crops, Page 25)

Water Needs for Pears

Stage 1 - Budburst and flowering to beginning of rapid shoot growth.
Tree water needs increase as cell division occurs and the canopy starts to develop. At the end of this stage you will a Crop Factor of 0.6. Tensiometer readings should be kept between 8 and 40 kPa. Spring rain will determine the amount of irrigation required.

Stage 2 - Beginning of rapid shoot growth to beginning of fruit fill.
During this stage of the cycle, fruit growth is slow and shoot growth rapid. The crop factor should be between 0.6 and 0.8 with soil moisture tension maintained at 8 - 40 kPa. If using RDI the crop factor can be 0.2 and the soil moisture can decrease to 200kPa.
Pear growth stages
Pear growth stages

Stage 3 - Beginning of fruit fill to harvest
Careful irrigation management is essential at this stage to allow rapid fruit growth and ensuring the largest potential size. Crop factors are 1.0 -1.1 and soil moisture tension should be held between 8 - 40 kPa.

Stage 4 - harvest to leaf fall
Post harvest tree water needs reduce but enough needs to be applied to maintain leaf cover and maintain tree health. Crop factor should be around 0.4 and soil moisture values can move to 200 kPa.

Stage 5 - Leaf fall to Budburst and flowering.
Trees are entering dormancy and no longer require water. soil moisture needs to be monitored carefully at the start of the spring to determine when first irrigations may be needed.

(Source: Guide to best practice water management - orchard crops, Page 26)

Water Needs for Apples

Stages 1 and 2 - Budburst and flowering to the beginning of fruit fill.
From the start of flowering and when the tree starts to produce leaves until the beginning of fruit fill, Crop Factor increase to 0.6. Soil moisture tension needs to be 8 - 40 kPa. There is no real time when the fruit grows slowly (apple fruit growth rate is steady from about 6 - 7 weeks after budburst until harvest). This means that crop factors will not vary sharply as for pears. It also means that there is little or no time to apply RDI (the fruit cells are either dividing or growing).

Stage 3 - Beginning of fruit fill to harvest.
Fruit continually grows at a steady rate. The crop factor increases to 0.8 before harvest. Soil moisture tension should be kept between 8 and 40 kPa.
Apple growth stages
Apple growth stages

Stage 4 - Harvest to leaf fall.
After harvest tree water requirements decline. The crop factor should be 0.4 but for continued health of foliage the Tensiometers should be kept between 8 - 40 kPa.

Stage 5 - Leaf fall to Budburst and flowering.
Trees no longer require irrigation because they are entering dormancy. Soil moisture still needs to be monitored at the start of spring to make sure irrigation is started prior to the next growth cycle.

(Source: Guide to best practice water management - orchard crops, Page 27)

Irrigation benchmarks 1998/99

Use this table as a general guide to tree water use and efficiency.

Water Applied (ML/ha)
Water Use Efficiency (t/ML)

Location
Crop
Irrigation System
No. of Sites
Average
Range
No. of sites
Average
Range

Shepparton
Pear
Micro
11
5
3.3-6.8
11
9.3
6.3-15.2

"
Sprinkler
1
6.3
-
1
12.9
-

"
Flood
3
6.8
3.6-10.3
3
8.5
6.6-10.5

Apple
Micro
1
4.2
-
1
24.8
-

"
Sprinkler
1
9.4
-
1
13.8
-

"
Flood
1
11
-
1
4
-

Peach
Micro
4
6.6
5-7.9
3
7.6
4.7-9.5

Cobram
Pear
Sprinkler
1
7
-
1
6.6
-

Peach
Micro
4
6.4
4.4-8.1
3
7.4
6-10.1

"
Sprinkler
1
7.1
-
1
9.6
-

Swan Hill
E.Peach/Nectarine
Micro
5
5.7
2.8-10.6
4
4.4
2.5-7.5

"
Flood
1
4.8
-
1
4.7
-

L.Peach/Nectarine
Micro
3
8.7
5.5-13.1
3
3.5
1.5-5.1

(Source: Guide to best practice water management - orchard crops, Page 85)

Its important you do this reguraly as allocation announcments are made. You may like to visit the Pirsa Website (External Site) for some more water budgeting tools.

Seasonal Water Allocations for Horticulture

The most important factor within any season and in particular dry seasons is your final allocation. Your opening allocation is generally set at the start of the irrigation season and may be adjusted during the course of the season as the storage's fill. It is for this reason that you may need to calculate your budget as frequently as new information becomes available.

In most years other than drought years, irrigators will receive an allocation that is equal to their water right, although in a drought, final allocation may be less than a water right.

Water Budget
There are three components necessary for developing a water budget:

Your estimated final allocation;
your predicted water use for the year on a monthly basis;
The volume of water that you have used to date in comparison to your predicted water use.

How to estimate a water budget for this season
To develop the budget you need to know:

What your water right is;
How much water you used last season;
how much extra water you used this season during the very dry period in August to the end of September this season;
what percentage of Water Right is likely to be allocated this season.

The estimated amount of water needed this season can be worked out in the following way:

Amount of water used last year
(usually a dry year as well)

Plus

The amount of extra water you used this season during the very dry period in August to the end of September.

Minus

Amount of water allocated by your water Authority this season.

As an example if you used a total of 320 ML (Water Right - 300ML - plus 20 ML extra bought last year) and used 50 ML to the end of September this year, it is likely you will need a total of 370 ML to get through this season.

Eg. 300 ML water right + 20 ML sales + 50 ML applied very early (Aug. + Sept.) = 370 ML needed this year.

However, if it is unlikely that 100% water right will be allocated you may find the following table useful to estimate how much extra water the example orchard above would need to purchase based on 50, 55 or 70% water delivery. It is clearly difficult to predict exactly how the season will turn out and it is up to you to decide what level of risk you will work out your figures from.

Your estimate of percentage water right this season.	Amount of water is normal water right is 300 ML	Estimated Irrigation water needed this year for above example.	Need to buy extra irrigation water.
50%	150 ML	370 ML	220 ML (370-150)
55%	165 ML	370 ML	205 ML (370-165)
70%	210 ML	370 ML	160 ML (370-210)

From the above table, if you think this years water allocation for the above farm is 50% of water right, then this example orchard needs to buy (or save) 220 ML of water.

Use the table below to estimate your own water requirements based on the above example:

Water Right plus sales from last year	This years extra irrigation (Aug. + Sept.)	Total needed this season	Anticipated amount of water for this season	Amount of extra water needed to buy or save
Example orchard: 300 + 20 = 320	50	320 + 50 = 70	50% of 300 = 150	370 - 150 = 220
Your orchard:

From early December onwards there is little chance of saving water by various management practices. This is already close to the rapid fruit fill stage for most of the fruit trees and full irrigations are required to make sure fruit reaches commercial size.

Trees should have been thinned to appropriate crop loads and some form of irrigation monitoring should be in place to ensure trees are not under or over irrigated.

(Source: DPI, Drought Preparation and Survival Guide - Horticulture, 2002)

Regulated Deficit Irrigation

You may like to read the article below and/or visit the RDI Demostration Site Journal that explians an actual demonstration site in a Tresco orchard.

With RDI, trees are kept short of water when fruit growth is slow or after harvest but are given ample water during the time of rapid growth of fruit. This reduces the growth of shoots. If RDI is properly managed, there is no reduction in the size of fruit or yield; in fact, both may increase - such results have been achieved. The reason why the above technique works relates to the growth pattern of shoots and fruit. On most deciduous fruit trees, the shoots grow rapidly early in the season, and their growth slows down as the fruit begins to grow rapidly. In contrast, early in the season the fruit grows slowly. Water stress at this time will reduce the growth of shoots without markedly affecting the growth of fruit.

With RDI, the irrigation season can be divided into four periods. The duration of these periods is determined by both weather and the relationship between vegetative growth and the growth of fruit.

Period 1
In this period, the trees are not irrigated, which allows the soil to dry out. With most crops this period follows flowering, however, with peaches there is initial rapid fruit growth following flowering when water stress must be avoided. In the Goulburn Valley trees are not irrigated until evaporation exceeds rainfall by 100 mm. If low rainfall during winter and early spring occurs or in environments dissimilar from the Goulburn Valley (for example, trees growing in lighter or deeper soil types), soil moisture must be measured. Irrigation should commence when the soil has dried out to 100 kPa in a sand or 400 kPa in a clay loam. In the Goulburn Valley this could be as late as mid-November in a wet spring or late October in a dry spring.

Period 2
Once irrigation commences, the trees are watered, but with greatly reduced volumes of water compared to that which would normally be applied. Irrigation replacements of pan evaporation of less than 30% are recommended. Period 2 commences at the initial irrigation and continues until six weeks before harvest for early-maturing fruits (that is, before mid-January), and eight weeks before harvest for later maturing fruits. Soil moisture in the middle of the wetted fibrous root zone should not exceed 100 kPa in sand or 400 kPa in clay loams.

Period 3 (from the end of period 2 until harvest)
In this period, the fruit is growing rapidly and the tree now needs ample water to maintain this growth. Water stress must not occur during this final period of fruit growth. Irrigation replacements of pan evaporation of 80 to 100% are recommended. Soil moisture in the middle of the wetted fibrous root zone should not exceed 40 kPa in sand or 60 kPa in clay loams.

Period 4 (post harvest)
After harvest a similar strategy as during period 2 can be implemented. In early maturing varieties and species (for example, cherries and apricots) there is considerable shoot growth after harvest which should be kept in check to maintain fruitfulness and even cropping within the canopy. Irrigation replacements of pan evaporation of less than 30% are recommended. Soil moisture in the middle of the wetted fibrous root zone should not exceed 100 kPa in sand or 400 kPa in clay loams.

(Source: Irrigation scheduling for regulated deficit irrigation (RDI) AG0299)

Soils

A soil survey is needed to determine how suitable a crop is for a particular soil type. It is also needed to determine how much water to apply at each irrigation.

A soil survey is made up of a series of sites where soil samples are taken, on a grid basis. They are selected on the basis of topography (land forms - slopes, rises, crests, flats), crop type and irrigation systems. At each site a vertical picture of a soil profile can be obtained by using an auger to remove a core of soil or by using a back hoe to dig a soil pit.

Soil Texture
Soils are like big sponges - they can only soak up so much water. When soils are fully wet there is little benefit in applying more water as this only causes waterlogging, drainage problems and loss of valuable fertilisers. How much water the soil can hold depends on the soil texture.

Soil Profiles
Soils from a vertical point of view are like a layered cake. At the top of the profile you have topsoil where most soil, water and fertiliser is extracted by the plant's roots.

Soils (depending on where you are located) may consist of several bands with varying characteristics and varying textures, and can be identified by the variation in colour. Eg see Tatchera sandy loam profile.

For instance, Within the Mallee you will find underneath the topsoil a layer of carbonate (known locally as the lime layer). The carbonate layer can restrict root growth, however some crops such as vines can partially penetrate the carbonate layer into the subsoil below. Defining your layers of soil and the type of carbonate layer will help to determine your plant's rootzone.

It is important when extracting soil for your sample from an auger hole that the soil is laid down in a line in the same order that it came from the hole. It is also very important that when digging the hole that you only go down 5 to 10 cm at a time. This avoids mixing the soils and provides greater accuracy when doing measurements and samples.

When using a hand auger it is easier to get information on topsoil depth rather than rootzone depth because it is often hard to find roots when sampling such a small volume of soil. In this case rootzone depth is estimated from topsoil depth. A back hoe pit makes locating the rootzone much easier.
Diagram: Showing Example rootzone depths
Diagram: Showing soil layers

Impermeable layers can be missed if you only sample to a depth of 1 metre, so it is wise to use a longer extension every few holes to sample down to a greater depth.

The depth of the rootzone and the depth of each layer of soil are very important for determining the soil's capacity for holding moisture.

(Source: Swan Hill Irrigation Management Course, Book 1, Chapter 1,B and C.)

Soil Texture

What are soils made of?
The texture of a soil is determined by the relative amounts of sand, (large particles) silt and clay (small particles) that it contains. Texture can be defined as the coarseness or fineness of a soil. The texture of each layer will determine how much water it can hold and how much is available to plants.

Clay - the very small particles less than 0.002 mm,
Loam - the particles in between 0.002 and 0.05 mm and
Sand - the coarse particles between 0.05 mm to 2.0 mm

The ribboning technique:
Take a sample of a soil layer sufficient to comfortably fit into the palm of the hand. Moisten with water, a little at a time, and kneaded until the ball of soil just fails to stick to the fingers. More soil or water may be added to attain this condition which is known as the sticky point, and approximates field capacity for that soil.

Kneading and moistening, if necessary, are continued until there is no apparent change in the soil ball, usually a working time of 1 to 2 minutes. Textures are recognised by the behaviour of the moist bolus when puddled in the palm of the hand, squeezed in the hand (coherence) or pressed (ribboned) out between the thumb and forefinger. A description of more common soil textures follow, along with approximate percentage of clay sized particles (includes fine earth carbonate).

Determining soil texture using the ribboning technique

(S) Sand	Coherence nil to very slight, cannot be moulded; single grains adhere to fingers; nil to slight turbidity when puddled.
(LS) Loamy Sand Will form a ribbon to 5mm	Slight coherence; definite turbidity when puddled in palm of hand.
(CS) Clayey Sand Will form a ribbon 5 to 15mm	Slight coherence, sticky when wet, many sand grains stick to fingers, discolours fingers with clay stain.
(SL) Sandy Loam Will form a ribbon of 15 to 20mm	Bolus just coherent and very sandy to touch; sand grains visible.
(LSCL) Light Sandy Clay Loam Will form a ribbon of 20 to 25mm	Bolus moderately coherent but sandy to touch; sand grains easily visible.
(L) Loam Will form a ribbon of about 25mm	Bolus coherent and spongy; smooth feel and no obvious sandiness; may be somewhat greasy as organic matter is usually present.
(SCL) Sandy Clay Loam Will form a ribbon 25 to 40mm	Bolus strongly coherent, sandy to touch; sand grains visible.
(CL) Clay Loam Will form ribbon 40 to 50mm	Bolus strongly coherent and plastic, smooth to manipulate.
(SC & LC) Sandy Clay and Light Clay Will form a ribbon 50 to 75mm	Plastic bolus, slight resistance to shearing. SC - can see, feel and hear sand grains. LC - smooth to touch.
(LMC) Light Medium Clay Will form a ribbon 75 to 85mm	Plastic bolus smooth to touch; moderate resistance to shearing between thumb and forefinger.
(MC) Medium Clay Will form a ribbon 85 to 100mm	Smooth plastic bolus: handles like plasticine and can be moulded into rods: moderate resistance to ribboning.
(HC) Heavy Clay Will easily form a ribbon over 100mm	Smooth plastic bolus; handles like stiff plasticine; can be moulded into rods without fracture; has firm resistance to ribboning shear.

(Source: Swan Hill Irrigation Management Course, Book 1, Chapter 1,B and C.)

Using Your Soil Data To Calculate The Readily Available Water (RAW).

Knowing how much water your soils can hold will make irrigating more productive, and irrigation planning much easier. Where there is lots of clay, the holes (pores) in the soil are smaller and the water is held very tightly. It is more easily extracted from the larger pores found between sand particles. The Readily Available Water (RAW) is the amount of water stored in the soil pores which can be easily used by plants.

We express readily available water as millimetres per centimetre of soil depth (mm/cm).

As mentioned, plants cannot extract all of the water held in the soil. We know that plants extract water using their roots, so only water in the soil where roots occur (the rootzone) is available for plants.

Calculating RAW:
Readily available water is calculated for each soil layer at each site using soil data from our soil survey and values from the table below.

Grade
8-40kPa
8-60kPa
8-200kPa
8-1500kPa

Sand (S)
0.36
0.38
0.40
0.62

Loamy Sand (LS)
0.52
0.55
0.58
0.87

Clayey Sand (CS)*
0.55
0.60
0.64
1.00

Sandy Loam (SL)
0.59
0.65
0.70
1.15

Light Sandy Clay Loam (LSCL)
0.65
0.74
1.03
1.37

Loam (L)
0.69
0.84
1.00
2.43

Sandy Clay Loam (SCL)
0.61
0.71
1.01
1.43

Clay Loam (CL)
0.53
0.65
0.73
1.48

Clays (SC,LC,LMC,MC)
0.46
0.57
0.66
1.49

Heavy Clay (HC)**
0.25
0.41
0.49
1.20

* Interpolated value. ** Samples from Kununurra W.A.

In the table above the water deficit (mm) per cm of soil depth indicates the amount of water required to bring the soil back to field capacity at a particular reading on a tensiometer.

The following exercise is for a fictional property but it will show you what to do with your information.

In order to bring a sandy loam from a refill point (40 kPa) to field capacity (8 kPa):

According to the table above 0.59 mm depth of water is needed for every centimetre depth of a sandy loam soil type.
If the layer is 50 cm deep, 29.5 mm (50 cm x 0.59 mm/cm) would be needed to bring that particular soil layer back to field capacity.

In order to bring a sandy loam from dry (60 kPa) to field capacity (8 kPa):

According to the table above 0.65 mm depth of water is needed for every centimetre depth of a sandy loam soil type.
As the layer is 50cm deep, 32.5mm (50cm x 0.65 mm/cm) of water is needed to bring that particular layer back to field capacity.

Thus, the drier the soil before irrigation, the more water is needed to bring that soil profile back to field capacity. On the other hand soils are like big sponges, which can only soak up a limited amount of water - when fully wet little benefit is gained in applying more water, as this leads inevitably to waterlogging, drainage problems and loss of valuable fertilisers.

(Source: Swan Hill Irrigation Management Course, Book 1, Chapter 1,D.)

Depth of the Rootzone

Rootzone Depth is the depth down to which roots are present. The rootzone may be deeper than the topsoil since roots of lime tolerant crops will grow down into a carbonate layer especially free-draining carbonate layers.

When you examine your soil profile look for healthy roots within each soil layer and record them. Record the rootzone on the basis of the number of roots per 10cm square.

0 No Roots

1 Few per 10 cm x 10 cm Square (1 - 10)

2 Many per 10 cm x 10 cm Square (10 - 25)

3 Common per 10 cm x 10 cm Square (25 - 200)

4 Abundant per 10 cm x 10 cm square (Over 200)

(Source: Swan Hill Irrigation Management Course, Book 1, Chapter 1,B and C.)
Diagram: depicting the rootzone depth of a plant.
Diagram: depicting the rootzone depth of a plant.

Basic Comparison of Monitoring Equipment

System	Advantages	Disadvantages
	Monitoring Soil Moisture Tension (kPa)
Tensiometers	Relatively cheap Easy to install Can be read by yourself Allows continuous monitoring	Labour Intensive to collect and record data Requires regular maintenance Can be inaccurate in extremely wet or dry soil
Gypsum Blocks	Relatively cheap Easy to install yourself Can be read by yourself Continuous monitoring possible	Labour intensive to collect and record data Requires a digital meter to be brought to each sensor site to take the readings Can be inaccurate in extremely wet soil
	Monitoring Total Soil Water Content
Neutron probe	Portable can be moved around sites Very reliable and accurate	Not suitable for continuous monitoring As the equipment is very expensive and contains radioactive material, it is generally used by consultants Less accurate in the top 10 cm of soil
Capacitance Probes Eg. Enviroscan	Continuous monitoring Accurate at all depths Enable rapid reading and recording of results	Expensive Need skill interpreting results

(Source: Guide to best practice water management - orchard crops.)

Example RAW Calculation

Layer Depth
25
cm

Deficit
0.61
mm/cm

Raw 1
15.25
mm

Layer Depth
50
cm

Deficit
0.53
mm/cm

Raw 2
21.2
mm

Raw 1 + Raw 2
15.25 + 21.2
mm

Total
36.45
mm

See the Information Notes:

Basic Comparison of Monitoring Equipment

System
Advantages
Disadvantages

Monitoring Soil Moisture Tension (kPa)

Tensiometers

Relatively cheap
Easy to install
Can be read by yourself
Allows continuous monitoring

Labour Intensive to collect and record data
Requires regular maintenance
Can be inaccurate in extremely wet or dry soil

Gypsum Blocks

Relatively cheap
Easy to install yourself
Can be read by yourself
Continuous monitoring possible

Labour intensive to collect and record data
Requires a digital meter to be brought to each sensor site to take the readings
Can be inaccurate in extremely wet soil

Monitoring Total Soil Water Content

Neutron probe

Portable can be moved around sites
Very reliable and accurate

Not suitable for continuous monitoring
As the equipment is very expensive and contains radioactive material, it is generally used by consultants
Less accurate in the top 10 cm of soil

Capacitance Probes Eg. Enviroscan

Continuous monitoring
Accurate at all depths
Enable rapid reading and recording of results

Expensive
Need skill interpreting results

(Source: Guide to best practice water management - orchard crops.)

Soil Moisture Monitoring

Soil moisture monitoring that relies solely on estimated RAW, evaporation and crop factors will run into problems.

Firstly, values of RAW are difficult to estimate and the amount of water applied with each irrigation may need to be modified.

Secondly, crop factors or coefficients may vary between orchards. Soil moisture monitoring will allow the crop factors or coefficient values to be adjusted for each orchard and will help you to irrigate each block in a more specific way.

Finally, soil moisture monitoring is also very important for deciding on the first irrigation and when to irrigate after rainfall. Soil moisture can be measured as either;

total soil water content, or
soil moisture tension (suction)

(Source: Guide to best practice water management - orchard crops.)

Visit Goulburn Murray Water (external link)

See the Information Notes:

Adjusting Irrigations

Monitor soil moisture before and after irrigation and adjust the maximum irrigation amount if;

soil is wet below the root-zone or,
soil is dry after irrigation

Also adjust the Crop Factor (and therefore maximum number of days between irrigations) if;

soil becomes to dry or,
remains to wet before a scheduled irrigation

(Source: Guide to best practice water management - orchard crops.)

Scheduling

The recommended irrigation scheduling system will utilise Crop Factors and Evaporation (Epan) or Crop Coefficient and Evapotranspiration (ETo), together with soil moisture monitoring to determine and adjust both the amount and timing of irrigations, A summary of the steps is as follows:

How much to irrigate
Step 1: Determine the irrigated root volume, from;

the wetting pattern and
the root distribution

Step 2: Estimate the maximum amount of allowable irrigation, from:

the irrigated root volume and
the percentage of RAW

When to irrigate
Step 3: Calculate the maximum number of days allowable between each irrigation for each month of the season based on:

maximum amount of allowable irrigation, and
average daily Epan and crop factor or ETo and coefficient

Step 4: Irrigation occurs after the number of days calculated in step 3. with volumes as calculated below.

	Flood or Knocker Sprinklers	Micro-irrigation
Irrigation Requirement (mm) =	Epan (mm) x Crop Factor	Epan (mm) x Crop Factor x Planting (m2)
OR
Irrigation Requirement (mm) =	ETo (mm) x Crop Coefficient	ETo (mm) x Crop Coefficient x Planting (m2)

(Source: Guide to best practice water management - orchard crops.)

Converting to Drip Irrigation

Drip irrigation applies water to the rootzone via plastic tubing, either with in line or button drippers. In line drippers are either pressure compensated or non – pressure compensated. Options for dripper type, output, spacing and filtration need to be carefully evaluated. In sandy soils more drippers are needed to wet an adequate volume of soil compared to a heavier clay soil, due to a narrower wetting pattern in sandy soils than in clay soils. Good filtration is vital due to the small size of the outlets – clogging due to precipitation of chemicals and /or organic matter (algae and bacteria) can easily occur, however most drippers these days are designed to be self cleaning.

System maintenance should include annual flushing of the system with chlorine or copper sulphate to avoid clogging problems. Drip systems should be flushed regularly to ensure that sediment or algae does not build up and block drippers. This should be done at least three times during the season. In some areas where water is of very poor quality flushing may need to be more frequent.

Fertigation/fertiliser injection can be an effective way of applying fertiliser. As it is being applied to the rootzone alone, little fertiliser is wasted and can be applied more regularly compared to broadcasting fertiliser. This is especially beneficial to young trees, vines and vegetable crops, which require small amounts of fertiliser regularly.
Diagram: Typical wetting pattern under drip irrigation

Diagram: Typical wetting pattern under drip irrigation
Diagram: Wetting pattern difference between sand, clay and loam soils

Diagram: Wetting pattern difference between sand, clay and loam soils

Advantages

Installation and pumping costs lower than with other systems.
Water distribution to rootzone uniform.
Highest water use efficiency of all above ground systems.
Weed growth reduced as less soil is wetted
Able to implement Partial Rootzone Drying
Foliage is not wetted
Suitable for Fertigation
Potential for precise control of vine/citrus stress
Pressure compensated drip suitable for undulating areas
Compaction of soils and access by heavy machinery less problematic due to less soil being wetted
Drip lines are easily shifted

Disadvantages

Small openings prone to blockage
Cover crops difficult to establish
Need of drippers to be close together in soils with poor lateral spread
No frost control
Additional cost is PRD used
Can cause water logging in heavy, poorly structured soils
Constant supply of water needed
Precise management and frequent use needed. May require automation
On sandy soil it may not be possible to wet a sufficient volume of soil
Fertigation only way of fertilising (i.e. not Superphosphate as it is not soluble enough)
Filter and maintenance level high
Higher standard of filtration required
Higher volume of back flush water required

Subsurface Drippers
Subsurface drippers discharge as low as 1l/h through a pressurised system similar to normal drip. The drip line is buried about 30-60 cm deep, depending on the soil type, structure and rooting depth. Due to root intrusion and pinching by the crop, tube wall thickness needs to be considered, as does the location of the tube. Dripper output needs to be carefully matched to the infiltration rate of the soil in order to achieve the desired lateral spread (which can be increased by pulsing the irrigation). Subsurface drippers can re-use effluent as the nutrients and bacteria applied are not exposed to the open air.

Advantages

See drip irrigation
Evaporative losses are minimal

Disadvantages

See drip irrigation
Blockages can not be detected
Water ‘chimneying’ to soil surface may occur
Back siphoning of soil particles into the emitter due to inadequate system design

(Source: Swan Hill Irrigation Management Course, Book 1, Chapter 2, F and G.)

Application Rate/Pressure Bench Marks

System Type
Optimum Pressure Range (kpa)
Discharge Range (l/hr)

Drippers
80 - 100
2 - 8

Microjets
100 - 150
25 - 200

Mini-sprinklers
125 - 200
35 - 350

Low-level
200 - 300
300 - 1200

Overhead
250 - 400
700 - 3000

(Source: Swan Hill Irrigation Managment Course, Book 1, Chapter 3)

Calculating Average Pressure

Sprinkler (or dripper) performance needs to be tested about every 3 - 5 years or more often depending on the water quality.

Pressures and discharge need to be periodically measured to ensure that the performance of the system remains at an acceptable standard. Decreasing the pressures through the build up of slime, or rust in the risers, alters the discharge and reduces the radius that sprinklers cover. The tendency is insufficient water in the centre of the diamond pattern resulting in weaker growth in that area.

Pressure can be measured in psi (pounds per square inch), kilopascals or centibars.

Some Important Conversions

1 Centibar (cb) = 1 kilopascal (kpa)

1 pound per square inch (psi) = 7 kpa (approx)

1 bar = 100 kpa

1 atmosphere is also = 1 bar

There are acceptable operating ranges for the different classes of sprinkler as seen in the Application Rate/Pressure Bench Marks table.

Application Rate/Pressure Bench Marks

System Type
Optimum Pressure Range (kpa)
Discharge Range (l/hr)

Drippers
80 - 100
2 - 8

Microjets
100 - 150
25 - 200

Mini-sprinklers
125 - 200
35 - 350

Low-level
200 - 300
300 - 1200

Overhead
250 - 400
700 - 3000

(Source: Swan Hill Irrigation Managment Course, Book 1, Chapter 3)

Measuring Sprinkler Pressures
Measuring selected sprinklers in each valve unit and performing a few simple calculations will tell

If the sprinklers are within their correct operating pressure range
What depth of water is applied at each irrigation
How much variation in depth of water applied there is across the system

The operating pressures of sprinklers need to be measured. Take measurements spread across each irrigation shift, while the irrigation system is operating under normal conditions.

For an irrigation system with a single sub-main, at least nine sprinklers should be checked. Systems with more sub-mains require more sprinklers to be checked.

The RULE is to check sprinklers nearest and furthest from the valves, at the start and end of laterals, and at points of high and low elevation.

Step 1:
Operate the irrigation system as per usual. For each section test sprinkler pressures and also record information on the sprinkler brand/model, nozzle size, crop type and spacing, and sprinkler spacing. Also record what other units are operating at the same time and the pressure at the pump.

Step 2a: Small Low-Level Sprinklers
Select the sprinklers, pinch off the lead tubing and unscrew the sprinkler from the stand or stake. Screw the pressure gauge and fitting onto the stand or stake and replace the sprinkler on top of the fitting. Release the lead tube and allow the sprinkler to operate normally and record the operating pressure of each sprinkler as indicated by the pressure gauge.

Step 2b: Large Under tree Sprinklers or Overhead Sprinklers
Select your sprinklers for measurement. Position the pitot tube and gauge on the main outlet of the sprinkler, with the point of the tube 3mm (1/8") from the nozzle in the stream of the water and record the value obtained from the gauge. For more information on pitot tubes visit the Oregan State University website.

Calculating Average Pressure
Add up all the pressures and divide the total by the number of readings.

Example:

Emitter	Pressure
1	150
2	155
3	150
4	160
5	170 (Highest)
6	160
7	145 (Lowest)
8	155
9	145
Total	1390 kPa
Average pressure = 1390 / 9	154 kPa

Pressure Variation
To calculate Pressure Variation, you need the Midpoint Pressure and the Difference. To get the Midpoint Pressure, add the highest pressure and lowest pressure and divide the result by two.

Using the example above:

Highest + Lowest	170 + 145 = 315
Divided by	2
Midpoint Pressure	= 157.5

To find the difference, subtract the lowest pressure from the midpoint pressure.

Using the same example agian:

Midpoint - Lowest	157.5 - 145
	= 12.5

Finally, to find the pressure variation as a percentage, divide the Difference by the Midpoint and multiply by one hundred.

Concluding the example from above:

Difference / Midpoint	12.5 / 157.5 = .079
By	100
Variation	= �7.9%

This is less than �10%, so it is acceptable.

(Source: Swan Hill Irrigation Managment Course, Book 1, Chapter 3)

Also visit the Information Note AG0137: Maintenance of Trickle Irrigation Systems

Checking Drippers

To ensure a drip irrigation system is operating correctly, regular measuring and recording of dripper outputs and pressures throughout the system is essential.

The discharge from a dripper, as stated by the manufacturer, is generally a nominal discharge figure at specific pressure and temperature. Most manufacturers nominate the discharge at 100 kPa (14.5 psi), which is generally the minimum recommended pressure for correct dripper operation.

In a properly designed system there will be less than about 10% variation in pressure throughout, to avoid having some plants under- and others over-watered.

Alternatively, self-compensating drippers, putting out a relatively constant discharge over a wide range of pressures, may be used. The discharge of some of these self-compensating drippers is normally controlled by a small rubber diaphragm, which may gradually harden when in contact with chemicals. Hardening of the rubber diaphragm causes an alteration to the discharge rate, making the replacement of the dripper necessary. To avoid over/under-watering random checks of dripper-output at several points throughout the system should be carried out on a regular basis. Following is an outline of a method suitable for checking dripper-outputs.
Equipment needed

Shovel
9 plastic containers of suitable size
2 litre measuring jug - measuring in millilitres
Watch/timer
Pressure gauge with tapered fittings
Paper to record results

Procedure

Place one container under a dripper towards each corner of the shift and one approximately in the centre of the shift, ensuring all water from the dripper is collected in the container.
Note location of the dripper on a sketch of the shift
Record the start and finish times
Measure and then record the amount of water collected in each container by tipping it into the measuring jug
Calculate the discharge each dripper would put out in one hour
Measure and record the pressure and discharge at the valve and at the end of several laterals.

A variation in dripper outputs of +/- 5% indicates the system is poorly designed, control block pressure is incorrectly set or there are some partial blockage problems.

Readings recorded using this system should be kept and compared each time a new set of readings is taken. This will allow any alteration in pressures and dripper outputs to be detected and rectified early on.

There should be one pressure gauge on each side of the filter bank at the pump. These gauges should be used regularly to monitor the performance of the pump filter to detect problems in the system. Another gauge should be kept in a protective container in the farm vehicle and used regularly to monitor pressures at control points and at ends of laterals throughout the vineyard.

Calculating Average Discharge
Add up all the discharges and divide the total by the number of discharges.

Example:

Emitter	Litres
1	42.5 (Lowest)
2	44.4
3	45.2
4	46.9 (Highest)
5	44.9
6	45.9
7	44.8
8	44.6
9	45.6
Total	404.8 l/hr
Average Discharge = 404.8 / 9	45 l/hr

Cartoon: The dog drank it, or we've got a problem

Calculating Discharge Variation
To calculate this you will need the Midpoint Discharge and the Difference. To find the Midpoint Discharge, add the highest discharge and lowest discharge and divide the result by two.

Using the example above:

Highest + Lowest	46.9 + 42.5 = 89.4
Divided by	2
Midpoint Discharge	= 44.7

To calculate the Difference, subtract the Lowest Discharge from the Midpoint Discharge:

Using the same example agian:

Midpoint - Lowest	44.7 - 42.5
	= 2.2

Finally, to find the Discharge Variation as a percentage, divide the Difference by the Midpoint and multiply by one hundred.

Concluding the example from above:

Difference / Midpoint	2.2 / 44.7 = .049
By	100
Variation	= +/-4.9%

This is less than � 5%, so it is acceptable.

(Source: Swan Hill Irrigation Management Course, Book 1, Chapter 3)

Checking Sprinklers

Measuring Sprinkler Discharge
At each sprinkler the discharge is measured for 30 seconds. The output for one hour is then calculated. Each sprinkler has a specified discharge when it is new.

Discharge (l/hr)

=

Water
Collected

Divided
By

Time
collected for

Multiplied
by

3600
(Seconds/hr)

Each sprinkler has a specified discharge when it is new. If wear and tear has effected the nozzle, the discharge figure above will be very different from the manufacturers recommendations, and will not be working efficiently (remember, worn nozzles can be checked using a drill bit).

Example:

Cartoon: Lets see what its like to rely on this sprinkler for a drink

If 1.58 litres was collected in the bucket from an emitter 30 seconds, the discharge will be:

189.56 (l/hr)

=

1.58

Divided By

30

Multiplied by

3600 (Seconds/hr)

Calculating the Application Rate
Application rate is the depth of water that a pressurised system applies to the soil surface in one hour.

Application Rate (mm/hr)

=

Discharge from Sprinklers (l/hr)

Divided By

Sprinkler Spacing (m) x Row Spacing (m)

Example:

4.7 (mm/hr)

=

189.6 (l/hr)

Divided By

7.3 (m) x 5.5 (m)

Average Irrigation Depth
The average irrigation depth is found by multiplying the Application Rate by the number of hours of the shift.

Average Irrigation Depth (mm)

=

Application Rate (mm/hr)

Multiplied By

Time (hrs)

Example for a 10 hour shift:

47 (mm)

=

4.7 (mm/hr)

Multiplied By

10 (hrs)

(Source: Swan Hill Irrigation Managment Course, Book 1, Chapter 3)

Application Rate/Pressure Bench Marks

System Type	Optimum Pressure Range (kpa)	Discharge Range (l/hr)
Drippers	80 - 100	2 - 8
Microjets	100 - 150	25 - 200
Mini-sprinklers	125 - 200	35 - 350
Low-level	200 - 300	300 - 1200
Overhead	250 - 400	700 - 3000

(Source: Swan Hill Irrigation Managment Course, Book 1, Chapter 3)

Checking a Pressure System

Starting at the pump shed;

1. Check that the motor is running normally and drawing the correct amperage. Listen for unusual bearing noises.

2. Examine the inlet side of the pump to ensure there are no obvious obstructions around foot-valves, screens etc. Replace any faulty or torn gaskets.

3. Check for any obvious leaks that are on the delivery side of the pump, and take appropriate corrective action.

4. Check to ensure that gate valves on the delivery side of the pump are appropriately open.

5. Filters should be clean and operating normally. If there are pressure gauges at both ends of the filter, the difference should be within specifications.

6. Monitor the pressure gauge on the delivery side and ensure that it is running at normal pressure. If unsure about the pressure that should be delivered, or the amperage that the pump should run at, contact the system designer.

7. Where there are flushing points on mains and sub mains or laterals, these should be opened to clear any obstructions. Make sure that the flushing points are the correct size for the system.

8. Ensure that the numbers of sprinklers on each shift are within the design standards of the system.

9. Sprinkler nozzles can be checked for wear by using drill bit shanks (preferably new). Nozzles usually have a nozzle size in mm, fractions of an inch, or a manufacturer’s code stamped on them or are colour coded. Select the appropriate sized drill bit shank to fit snugly in a new nozzle.

Overhead Sprinkler Systems

1. Replace any sprinkler washers if there is leakage down the riser, or other signs of wear.

2. Note the speed of rotation of the sprinkler – it should to manufactures specifications.

3. Check the knocker arm rate, this should be about 3 times per second or 180 per minute (almost too fast to count).

4. Check sprinklers across the shift at the top, middle and end of the laterals.

5. Check sprinklers in shifts across all sub-mains to ensure uniformity.

6. Check the cost of refurbishment of the sprinkler to its replacement cost. It is sometimes cheaper to buy a new one.

7. If replacing a sprinkler in a system with a different brand or type, ensure that the specifications of the new sprinkler are similar to the old one. They should have similar discharges and wetted diameters, as well as operate at the same pressure. Check with your designer before putting in a different make or model.

Low Level Systems

1. Repair any leaks in the poly-lines, lead tubes, drag hoses or other pipe work. Check for leaks, particularly where the lead tube joins into the lateral.

2. Check that the knocker arm or spinner is operating properly, and the sprinkler is rotating at the correct speed. Replace the washer in the sprinkler if required.

3. Clear the area around the sprinkler of any foliage or weeds to ensure good distribution.

4. Check sprinklers across the shift at the top, middle and end of the laterals.

5. Check sprinklers in shifts across all sub-mains to ensure uniformity.

6. Check the cost of refurbishment of the sprinkler to its replacement cost. It is sometimes cheaper to buy a new one.

7. If replacing a sprinkler in a system with a different brand or type, ensure that the specifications of the new sprinkler are similar to the old one. They should have similar discharges and wetted diameters, as well as operate at the same pressure. Check with your designer before putting in a different make or model.

(Source: Swan Hill Irrigation Managment Course, Book 1, Chapter 3)

Why is Salinity Important?

Constant shallow watering during drought periods can result in elevated levels of salts in the top soil. Salinity results in rapid uptake of salts to toxic levels, This can badly damage or kill trees. Fruit tree's are generally considered to be sensitive and a reduced yield can be experienced even with fairly low levels, because:

water is naturally attracted to higher salt levels - if soil is high in salt, it binds the water strongly and becomes difficult for the tree to extract (ie. in effect, the saline soil reduces the available water)
excesses in some salts (Eg. sodium and chloride) can poison the tree.
excess salts taken up by the tree are stored in the woody tissues

Symptoms of salt damage include:

leaf burn
leaf drop
reduced vigour, yield and size
trees may appear wilted (despite moist soil)
chloride and sodium present in leaves.

Species of Fruit	Salinity at initial yield decline (threshold) (ECe)	Yield decrease per unit increase in salinity beyond the threshold (%)
Apple	1.0	18
Almond	1.5	19
Apricot	1.6	24
Grape	1.5	9.6
orange	1.7	16
Peach	1.7	21
Plum	1.5	18
Pear	1.0	-

(Source: Guide to best practice water management - orchard crops, Page 51-53)

Soil Sampling Procedures

General Sampling Guidelines

Take cores from at least 30 sites evenly distributed over the block or section of a block. A grid pattern should be used to determine the site locations (See Diagram).

Cores should be taken from spots of average growth or poorer spots if they predominate. Remember that you are trying to get an "average" sample that is representative of the entire area.

For most horticultural crops cores should be taken from 0-150 mm (0-6 in) and 150-300 mm (6-12 in) depths separately and later combined into one sample. Remove each core carefully from the sampler using a clean screw driver or similar tool and place it in a clean plastic sample bag or other suitable container.

At least 30 cores should be taken from the area being sampled and placed in a clean bag or other suitable container. The more cores that are taken the more representative the sample will be.

Diagram: Recommended sampling sites for established crops - row crops
Diagram: Recommended sampling sites for established crops - row crops

If you have more than the amount of sample required by the laboratory it will be necesary to sub-sample. Place the sample in a clean container, break up the clods and spread the total sample evenly on a clean bench. Divide the sample into four quarters, discard the two diagonal quarters and place the remaining samples in a clean container.

Transfer the cores or sub-sample into a clean sample bag if you have not already done so and seal the bag. Mark the bag with the block or section name, the number of cores taken and the depth of the sample.

Your samples are now ready for dispatch to the laboratory. Be sure to provide all the information requested by the laboratory processing your samples to ensure that the best possible recommendations can be made.

Sub-surface Soil Sampling
Sampling of the sub-surface soil may be required where:

soil structural problems may exist;
deep rooted plants are not growing well; or
salt is suspected of being a problem.
It is recommended that at least two subsoil depths are always sampled. Examples of the depths to sample are presented in Figure 5. Each composite sample should consist of soil cores from at least 15 sites evenly distributed across the paddock. Where the depth to the clay layer in a soil varies, sample to the top of the clay layer and then sample the clay layer as a separate sample.

When collecting subsoil samples be careful not to contaminate them with scrapings from other soil layers. Because the chemical properties of soils vary dramatically with depth, even minor contamination of subsoil samples can make the interpretation of chemical results very difficult.
Diagram: Recommended subsoil sampling depths - showing a marked change in colour or texture and soils showing a gradual change in colour or texture
Diagram: Recommended subsoil sampling depths - showing a marked change in colour or texture and soils showing a gradual change in colour or texture.

It is recommended that soils are sent to a certified laboratory for analysis. A list of certified laboratories is available from the Australasian Soil and Plant Analysis Council (ASPAC) (external link).

(Source: How to Sample Soils Used for Flower, Fruit, Grape and Vegetable Production, AG0376)

Salt Sensitivity?

Irrigation scheduling and soil moisture monitoring will be vital in the management of saline irrigation area's.

The following table can be used as a guide.

Soil salinity levels should generally be kept below 2.0 dS/m (ECe) for fruit trees.

Sensitivity of various crops to salt.

Sensitive Moderate sensitivity Moderate tolerance Tolerance

Apple Grapes Squash Salt Bush

Apricot Potato Zucchini Olives

Cherry Tomato Ryegrass Date Palms

Citrus Lucerne Strawberry Clover

Peach Barley

Pear

Plum

General salt tolerance levels.

ECe dS/m Result

0 - 0.5 Very low salinity; all crops will grow

0.5 - 2.0 Low soil salinity; level is generally safe for fruit trees.

2.0 - 3.0 Soil salinity slightly above threshold for fruit trees; leaching management will be needed to reduce salinity.

> 3.0 High soil salinity for fruit trees; specific management needs to be adopted; grow more salt tolerant crops. If levels are above 3.0, further investigation will be required.

Recommended maximum soil EC levels for fruit production

Soil Type
EC1:5 (dS/m) Quicker Measurement
ECe (dS/m) Standard
Measurement

Medium Clay
0.27
2.0

Loam
0.21
2.0

Sandy Clay Loam
0.14
2.0

(Source: Guide to best practice water management - orchard crops, Page 52)

Soil Salinity Bench Mark Data?

Soil Sample results Will give Electrical Conductivity (ECe) values, which is a measure of the soil salinity. The tables below show benchmark data collected from 40 growers in Ardmona, Cobram, Shepparton East and Swan Hill.

Location	Soil ECe (dS/m) 0 - 25 cm Depth				Soil ECe (dS/m) 25 - 45 cm Depth
	1997 - 98		1998 - 99		1997 - 98		1998 - 99
	Average	Range	Average	Range	Average	Range	Average	Range
Ardmona	0.55	0.27 - 1.24	1.27	0.73 - 1.93	0.46	0.30 - 0.56	1.25	0.73 - 2.22
Shepparton East	0.69	0.21 - 2.23	1.02	0.44 - 2.61	0.59	0.21 - 2.27	0.93	0.32 - 2.58
Cobram	1.26	0.05 - 4.52	1.76	0.79 - 3.48	1.54	0.26 - 5.33	2.90	0.77 - 4.42
Swan Hill	1.67	0.48 - 4.65	1.03	0.82 - 1.35	1.47	0.51 - 4.31	0.98	0.58 - 1.59

(Source: Guide to best practice water management - orchard crops, Page 91)

Why Control Weeds?

Mulching reduces competition for moisture from weeds.

Eliminate all weed competition. If your orchard is micro-irrigated, spray weeds emerging in the irrigated zone during spring and summer. Slash the orchard more often and as close to the ground as possible. Spraying out all the under storey pasture and weeds may be needed under drastic water shortages.

(Source: Dry Season Information: Apples, AG1034 and Guide to best practice water management - orchard crops, Page 71 )

Why Mulch?

Mulching can benefit water use by improving soil structure. Soils higher in organic matter have a higher capacity to retain moisture. If possible, mulch the tree-line (after the frost danger period has passed) and irrigate the soil shaded by the tree and not out in the traffic row area.

If mulching with straw is possible, especially for young trees, irrigation emitters are best put under the straw next to each tree. It is important to keep the amount of exposed wetted surface to a minimum.

(Source: Dry Season Information: Apples, AG1034 and Guide to best practice water management - orchard crops, Page 71 )

Why Night Irrigation?

Irrigating at night will significantly reduce the amount of water lost to evaporation from the soil surface. A check of the FruitCheque Weather website indicates that Swan Hill pan evaporation in January can average 8 mm/day.

(Source: Drought Preparation and Survival Guide, - Horticulture, 2002 and FruitCheque Weather Website.)

Why No Wind Irrigation?

Windy conditions increase the rate of evaporation. According to the laws of physics the faster the water molecules are removed the faster they will be replaced by more. Hence wind has the effect of increasing evaporation by facilitating this effect. Wind also ruins the distribution pattern of sprinklers.

(Source: Wikipedia.)

Why Shorter Irrigations?

Avoid over watering your crops. Over watering cause water to escape into the water table. That water is wasted or can lead to other problems such as root rot, oxygen deficiency, salinity or other nutrient imbalances from concentrating or washing them out. Your soil can act as a reservoir of water but it is not a bank! Days between irrigations cannot be doubled simply by doubling the amount of water being applied during one irrigation. See other documents on RDI, Water Needs for Stone Fruit, Water Needs for Pears, Water Needs for Apples and Soil Moisture Monitoring for more specific information.

(Source: Drought Preparation and Survival Guide, - Horticulture, 2002)

Wind Break Water Use

Simply multiply the length in metres of the windbreak by the flow rate per metre of the irrigation tube to find out how much water your windbreak use's.

In extreme water shortages wind breaks should be sacrificed. Many will still offer protection from wind even while they are dead or dying. Wind breaks planted with natives may compete with you crop. Consider using a ripper to prune the roots, being careful not to make them unstable. Natives will, as a general rule withstand periods of low moisture availability. If you have windbreaks planted with non-drought tolerant species it may be an opportunity to plant them or build non vegetative wind structures.

A quick calculation should indicate the amount of water used by windbreaks.
Image: Casuarina cunninghamia, commonly used native wind break.
Image: Casuarina cunninghamia, commonly used native wind break

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This is ultimately your decision. Do this early, so you have time to consider all avaialable options and information before making important decisions. You will need to consult with whom you normally supply your fruit to and you may also need to consult with a free Rural Financial Counselling Service (external link).

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