There is a subtle difference between growing a fruit tree and producing a fruit crop of good quality and quantity on the North Coast; the major constraint upon us is water, for although we live in a relatively high rainfall area the distribution and reliability is quite poor as the last few years have demonstrated.
Is there enough water for everyone to irrigate? There are about 3,100 licensed irrigators on the North Coast, and a recent survey suggest that only 59% of respondents believe that they had sufficient water to adequately irrigate their enterprise, whilst in 23% of cases they had to resort in utilising more than one source of supply. A minority of about 6% did not believe that irrigation was necessary for their enterprise or in a high rainfall area.
The overall consensus is that there is not enough water, and this is borne out by the announcement that an embargo on all new irrigation licenses has been placed on most of our North Coast valleys. (Richmond, Clarence, Bellinger, Nambucca, Hastings and Camden Haven) This is a clear indication there has been an over commitment of the water resources. Our only option is to get smarter with the use of water. In some industries future development could be inhibited.
A catalyst to the placement of the embargo was the community's
concerns for the state of our streams, and it is clear that there
is a need for the retention of environmental flows to maintain
a healthy and sustainable system. The retention of environmental
flows will reduce the supply of water available for irrigation
needs. Those who wish to see what future direction water policy
and management may take should read "The Community's Concerns
About Water" produced by NSW Department of Land and Water
Conservation which reported on the community workshops conducted
on the North Coast in September - November 1994. Many factors
have to be considered to be able to obtain maximum production.
The success or failure often starts with the choice of the property
which should take into account such things as soil type, its depth,
fertility, drainage and climatic requirements for the enterprise,
but very often the available water supply is overlooked, and this
may have dire consequences.
**Insert Graph**
How much water is needed?
| Avocados | 3 | 0.7 |
| Bananas | 4 | 1.4 |
| Coffee | 3 | 1.0 |
| Custard Apples | 2 | 0.5 |
| Kiwifruit | 3.5 | 1.0 |
| Limes | 3.5 | 0.7 |
| Lychees | 3 | 0.7 |
| Macadamias | 3 | 0.7 |
| Mandarins | 3.5 | 0.7 |
| Pawpaws | 2 | 1.0 |
| Passionfruit | 2.8 | 0.8 |
| Pecan | 6 | 1.2 |
| Persimmons | 3 | 0.7 |
| Stonefruit | 5 | 1.0 |
#ML/ha = Megalitres per hectare
L/s/ha = Litres per second per hectare
However this is only the start, and a potential grower needs to ensure that an infrastructure of housing, electricity, irrigation and water supply schemes, licensing have been considered in conjunction with finances.
What will irrigation cost? The cost of irrigation may vary considerably with the size of the scheme, distance from the source of supply, property configuration, motive power (diesel or electric), and the duty for which it is designed, and inclusions (filtration, fertiliser injection and control gear), however for drip, micro spray and micro sprinkler irrigation schemes $3,000 per hectare is a good guide. To fully appraise the benefits of irrigation, a survey and design are necessary. A good designer will provide an itemised quotation, performance details of the irrigation scheme, and details of running costs.
Good water management can make a dramatic improvement in yields and quality, and in some cases can more than double production. The main benefit is being able to provide a long line at consistent quality. The grower can either use a consultant to advise when to irrigate and diagnose other problems (such as compaction, waterlogging, infiltration and deep drainage), or use a vast range of irrigation scheduling methods/tools. Consultants tend to use more sophisticated monitoring gear such as the EnviroSCAN and Neutron Probe, and combine other services (soil testing, petiole sap analysis, and integrated pest management).
A grower can use :
# A training school may be required to gain maximum benefit in interpreting data from these tools.
The cost of either employing a consultant, or purchasing some of the more sophisticated equipment will depend on the size of their operation or scale of the problem that you may have. Understandably, the results from the EnviroSCAN which gives continuous soil/water monitoring is more powerful than a manual weather based budgeting system.
There is an irrigation scheduling tool that everyone can afford.
Many farmers have purchased computers to assist in their children's education, with the hope that they may be able to undertake some of those laborious accounting chores that are necessary to stay in business and ahead of the tax man.
To promote more efficient water use, NSW Agriculture are offering a free irrigation scheduling software package that may allow you to use the computer to advantage, all you have to do is contact me at the Wollongbar Agricultural Institute or telephone me on 066 261353 and this irrigation scheduling computer software model will be set up specifically for you and any other crop you may be growing.
If you already have a computer with any of the popular spread sheets loaded, such as Excel, Quatro-Pro, Lotus 123, or the one in your Works program, then you will be able to use the computer model to schedule without any further cost. This Department has a number of weather stations located on the North Coast at Macksville, Coffs Harbour, Grafton, Alstonville, Modanville, Palmwoods, Kyogle, and Tweed Valley, so just advise me of the following:
Because the computer program is in the form of a spread sheet, other comments regarding insect attack, treatments, and production figures can be recorded for latter comparison. It is intended to run workshops at the end of the growing season to demonstrate how to graph your data, set up the program for the coming year, compare production results, and allow feed back to me concerning any problems that may have been encountered.
It is important however that you understand some of the principles involved in this weather based irrigation scheduling technique before you get started. The soil texture, structure, organic matter in the soil, root depth and stage of development will determine the amount of water and the interval between irrigations. If a soil is saturated, most of the soil pore spaces are filled with water forcing out the air. If this waterlogged condition continues an anaerobic state can lead to root death and production loss through Phytophora. At the other end of the scale, the tree can be stressed if the soil is allowed to dry out too far, and the tree roots to have work against the soil/water surface tension. This stage is known as the wilting point, and production also suffers.
The trick is not to allow the available soil moisture within the root zone of the crop to deplete by more than 50 percent. You will note that the Cumulative Etc will automatically commence as if the soil/water content is full. Therefore you will need to commence monitoring after there has been either sufficient rainfall or irrigation to fill the profile.
By way of example, avocado's grown in a red kraznozem soil on the Alstonville Plateau may hold 112 mm of water in every metre of soil, therefore we would use a cumulative evapo-transpiration (Etc) figure of 34 mm which is derived from 50% x 0.6 metre root depth x 112 mm of available soil moisture. Similarly, with say kikuyu/clover on a heavy clay loam around Casino may hold 150 mm of water per metre, one should use a 19 mm cumulative evapo-transpiration figure, derived from 50% x 0.25 m x 150 mm of available soil moisture.Water holding capacity of soils
| Sand | ||
| Fine sand | ||
| Sandy loam | ||
| Loam | ||
| Silt loam | ||
| Loamy sand | ||
| Clayey sand | ||
| Sandy clay loam | ||
| Light clay loam | ||
| Clay loam | ||
| Heavy clay loam | ||
| Clay | ||
If you want to give this computer model a try then it will be set up for you on a 3½" diskette with:
The crop factors that are used have been derived from actual tree water or pasture usage, assuming cultural practices common in this area. A crop factor may be affected by the climactic conditions, ground cover, species and root stock, and pruning, all these factors could impact upon the accuracy of a weather based program.North Coast Crop Factors
| Crop/Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
| Avocado | 0.8 | 0.8 | 0.8 | 0.4 | 0.4 | 0.4 | 0.5 | 0.6 | 0.7 | 0.8 | 0.8 | 0.8 |
| Banana | 0.9 | 1.05 | 1.05 | 1.05 | 1.0 | 1.0 | 1.0 | 0.8 | 0.75 | 0.7 | 0.7 | 0.75 |
| Citrus | 0.75 | 0.75 | 0.75 | 0.8 | 0.8 | 0.75 | 0.75 | 0.75 | 0.8 | 0.8 | 0.8 | 0.5 |
| Custard apple | 0.6 | 0.7 | 0.7 | 0.8 | 0.8 | 0.8 | 0.8 | 0.8 | 0.7 | 0.5 | 0.4 | 0.5 |
| Coffee | 0.7 | 0.7 | 0.7 | 0.7 | 0.6 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.8 | 0.8 |
| Kiwifruit | 0.78 | 0.78 | 0.72 | 0.72 | 0.61 | 0.01 | 0.01 | 0.61 | 0.78 | 0.83 | 0.9 | 0.9 |
| Lychee | 0.8 | 0.8 | 0.8 | 0.3 | 0.3 | 0.3 | 0.4 | 0.5 | 0.6 | 0.7 | 0.7 | 0.8 |
| Passionfruit | 0.8 | 0.8 | 0.7 | 0.6 | 0.6 | 0.6 | 0.6 | 0.6 | 0.6 | 0.7 | 0.8 | 0.8 |
| Papaw | 0.7 | 0.7 | 0.7 | 0.01 | 0.01 | 0.01 | 0.01 | 0.3 | 0.5 | 0.6 | 0.7 | 0.7 |
| Persimmon | 0.8 | 0.7 | 0.7 | 0.5 | 0.01 | 0.01 | 0.01 | 0.01 | 0.5 | 0.7 | 0.8 | 0.8 |
| Stonefruit | 0.8 | 0.7 | 0.5 | 0.01 | 0.01 | 0.01 | 0.01 | 0.65 | 0.85 | 1.0 | 1.0 | 0.9 |
| Pasture | 0.75 | 0.75 | 0.75 | 0.75 | 0.75 | 0.75 | 0.75 | 0.75 | 0.75 | 0.75 | 0.75 | 0.75 |
It is suggested that those using the program should use their own rainfall and evaporimeter records that best reflect what is happening on farm. Alternatively, weekly evaporation readings that appear in the Thursday edition of the Northern Farmer can be divided, so as to derive average daily readings, which are then entered in the Pan evaporation column. This computer program is fairly straight forward, and with use, a greater understanding of irrigation scheduling will be gained.
With increased interest by the Environmental Protection Authority (EPA), in the monitoring of stream flow quality, it is obvious that greater scrutiny will be placed on riparian landholders in the future. The application of fertilisers in high rainfall area's can be difficult, and the only solution is to apply small but frequent applications to avoid leaching and wastage.
The most efficient method of applying some fertilisers is through the irrigation, and has been used successfully by many growers because it saves labour, fuel costs, and reduces compaction due to less traffic. Soluble fertilisers can be leached down the soil profile to a depth of 20 cm where the most active root growth generally occurs. A reliance on rain for incorporation, runs the severe risk of tie up in the soil surface (light rain), leaching past the root zone (heavy rain) or loss through runoff (intensive rain).
The main points to remember about fertigation:
In summary, by adopting irrigation scheduling and fertigation
techniques you will be working in harmony with nature in a sustainable
manner, generating a consistent quality product, and optimising
profit.
Editors Note: The author included several very detailed tables (13 columns x 100 rows) of output, from the model described, as appendices to the original document. Due to the constraints of the presentation medium, I am unable to satisfactorily render them. If you require clarification in relation to these tables, please contact the author.