Physical Sciences and Mathematics Commons^™

Increasing Groundwater Salinity In The Northern Wheatbelt, R J. Mcgowan

Journal of the Department of Agriculture, Western Australia, Series 4

Every farmer in western Australia's northern wheatbelt will know of a groundwater supply, be it bore, well or soak. that has become increasingly saline. The groundwater may have become more saline over a period of 15 years or more, or have been noticed only recently. Inevitably, the bore will lie within an area cleared for agriculture. This increase in groundwater salinity may be associated with soil salinisation. Although researchers have some understanding of the processes causing salinisation of groundwater in the wheatbelt and the extent of the problem, little is known about the rates of salinisation and groundwater rise. A …

Draining Irrigation Areas, K S. Cole, J P. Middlemas

Journal of the Department of Agriculture, Western Australia, Series 4

Many irrigation schemes throughout the world have turned into unproductive saline flats and swamps. This dramatic change can occur within a few years of irrigation starting and has been part of irrigation schemes from earliest times up to the present day.

The main cause of this salinisation is normally excess irrigation water use combined with poor drainage. Any form of waterlogging will have an adverse effect on plant growth.

Sub-Surface Drainage Methods For Salinity Control, P R. George

Journal of the Department of Agriculture, Western Australia, Series 4

Sub-surface drainage can control waterlogging and salinity of arable land by removing excess groundwater.

There are two broad types of sub-surface drainage: interception drainage and relief drainage.

The cost of drainage will depend on the specific design for the site. For relief drains the prime determinate of cost will be the required spacing. In general, clay soils of low permeability or seepage areas will need narrower spacings and will be harder and more expensive to reclaim than sands or areas only needing drainage of local water.

Drainage To Control Waterlogging, D J. Mcfarlane, T R. Negus, J W. Cox

Journal of the Department of Agriculture, Western Australia, Series 4

Drains can be classified in several ways. Drains on flat land have similar drainage effects on either side of the drain and are called relief drains. Drains on sloping land intercept seepage water moving down hillsides and therefore have most effect on the downslope side. They are called interceptor drains.

Drains can also be classified as being open drains (that is, open at the ground surface) or buried drains (for example, tube drains).

Assessment Of Waterlogged Sites, D J. Mcfarlane

Journal of the Department of Agriculture, Western Australia, Series 4

Soil is said to be waterlogged if any part of the plant root zone is saturated with water. In severe cases soil is saturated to the surface and waterlogging is obvious. Waterlogging is distinguished from flooding in which surface runoff brings down water from higher up in a catchment. However, flooding may result in waterlogged sites.

Saltland Drainage : Case Studies, P R. George, R A. Nulsen

Journal of the Department of Agriculture, Western Australia, Series 4

Over the past five years farmers have become increasingly interested in the use of drainage to overcome saltland problems.

Experimental work by the Department of Agriculture on sub-surface drainage includes tube drainage and drainage by pumping. The Department is also monitoring the performance of open drains installed by farmers. Major sites are at Esperance, Dalwallinu, Namban and Watheroo.

Some of these projects have been reported in an earlier issue of the Journal of Agriculture. In this article P. R. George, Research Officer and R. A. Nulsen, Principal Research Officer with the Salinity and Hydrology Research Branch, discuss recent results from …

Laser Levelling Land For Flood Irrigation, M D. Green, J. P. Middlemas

Journal of the Department of Agriculture, Western Australia, Series 4

Since the introduction of laser levelling to Western Australia's South-West irrigation area five years ago, many farmers have benefited from this new and precise method of land-forming.

The use of lasser controlled earthmoving equipment to redevelop irrigated paddocks has led to improved irrigation efficiency and drainage. Less water is used for each irrigation, water is applied more evenly and less labour is needed. many older, grass-dominated paddocks have been reseeded to improve pasture species.

Eradicating Fruit Fly From Carnarvon, Kingsley Thomas Fisher

Journal of the Department of Agriculture, Western Australia, Series 4

Late last year the Mediteranean fruit fly (Ceratitis capitata Weidemann) was eradicated from Canarvon, Western Australia by using an intergrated programme of sterile insect releases and bait spraying.

The eradication marked the end of a four-year study on the use and effectiveness of the Sterile Insect Technique, a biological control technique which uses an insect pest against itself. such a study can be used as a basis for treating other threatening insect pests, such as the serious cattle pest screw-worm fly, should they be found in Asustralia.

Being a biological control method, the Sterile Insect Technique is an exellent …

Water Quality For Irrigation, P R. George

Journal of the Department of Agriculture, Western Australia, Series 4

Although irrigation and salinity problems are frequently inseperable, there is a range of management methods that can be used to handle marginal quality water. Freuently these methods are simple, but require careful planning.

The wide range in tolerance of crops to salinity can be exploiter to ensure that appropriate crops are selected for the water available.

Because crops vary in their sensitivity to salt uptake in the leaves or the roots, watering methods can be changed to avoid problems. For profitable production enough water should be applied to ensure adequate water is available for plant growth as well as to …

Salinity Control In Northern China, G A. Robertson

Journal of the Department of Agriculture, Western Australia, Series 4

China has vast areas of saline land, perhaps as much as six million hectares. Some of this saline land is a result of marine influence in coastal areas and some is the resultof soil formation in areas with saline geological deposits and inadequate rainfall to leach out the salts at that time.

However, most saline soils in China are as a result of secondary salinisation processess induced by a hydrological imbalance resulting from over-clearing of the land or irrigation. This imbalance has produced rising watertables bringing the salt closer to the soil surface.

In this article, G..A. Robertson, Commissioner …

Residual Values Of Australian Rock Phosphates, Michael D A Bolland

Journal of the Department of Agriculture, Western Australia, Series 4

For years superphosphate has been the cheapest, convenient and most effective way of supplying phosphorus to newly cleared soils in Western Australia's South-West that are acutely deficient in phosphorus. However its effectiveness as a phosphorus source falls markedly after application. Regular applications are needed to maintaine profitable pastures and crops on these soils.

After a big jump in supperphosphate prices in the mid 970s, researchers tested the use of Australian rock phosphates as potentially cheaper alternative phosphorus fertilisers to superphosphate. On the none-leaching sands, as this article shows, none of the rock phosphates was as effective for plant growth as …

Water Supplies : Dams And Roaded Catchments, W J. Burdass, T. R. Negus, A. L. Prout, I. A. F. Laing

Journal of the Department of Agriculture, Western Australia, Series 4

Western Australia's Upper and Lower Great Southern statistical areas include most of the broad-scale agricultural land south of a line from Perth to Hyden. Much of the area is well-developed and carries 13.4 million sheep, 203 00 cattle and 95 000 pigs, almost half the State's livestock.

There are few natural rivers and lakes to water livestock in summer and much of the bore water is salty. On-farm waterr conservation, therefore, consits mainly of excavated earth tanks (dams) which are filled by surface runoff or shallow seepage. In the drier areas and in the sandplain roaded catchments have neen built …

Dam Site Selection In The North-Eastern Wheatbelt, J L. Frith

Journal of the Department of Agriculture, Western Australia, Series 4

Western Australia's wheatbelt farm dams are dug three to eight metres deep and are generally sited in soils which either are inherently impermeable or can be made so during construction.

In the eastern and north-eastern wheatbelt, however, only a small proportion of the soils meets these criteria. Dam site selection in these areas therefore depends on a good knowledge ofwhich soils aresuitable and on our being able to locate them efficiently by using surface indications such as surface soil, natural vegetation or topographic features.

Northern Wheatbelt Water Supply Study, I A F Laing, R. M. Pridham

Journal of the Department of Agriculture, Western Australia, Series 4

Department of Agriculture surveys have shown that many farms in Western australia's northern wheatbelt have inadequate water supplies. More than 80 per cent of all farms in that area depend soley on groundwater for watering livestock, a much higher percentage than for most other farming areas. Because groundwater salinities have increased in recent years, concern is held for the long-term future of this recource.

In contrast to more southern agricultural areas, farm dams in the northern wheatbelt are relatively uncommon. Only 30 per cent of the existing dams in the northern wheatbelt constitute effective water supplies. More than half of …

Interceptor Drains And Waterlogging Control, J W. Cox, T R. Negus

Journal of the Department of Agriculture, Western Australia, Series 4

Department of Agriculture trials of seepage interceptor drains from 1972 to 1983 primarily assessed the effects of such drains on salt encroachment. Although these trials showed that the drains had little influence on salt storage within the topsoil, they did reduce waterlogging downslope.

To investigate this drainage effect further, the Department's Narrogin office surveyed 35 drains on 14 properties in the winter of 1981, followed by detailed crop measurements in December that year. Provided the drains were properly designed, surveyed and constructed, and well maintained, they could be expected to increase crop yields during a waterlogging year by about 1 …

Farm Debt In The Wheatbelt : 1984 Survey Results, R S. Kingwell

Journal of the Department of Agriculture, Western Australia, Series 4

In recent years many farms in Western Australia's wheat-growing areas have experienced adverse seasons. For example, the 1983-84 season was characterised by a late start, dry spring and wet harvest which resulted in many farms suffering a combination of low yields and the downgrading or dockage of their grain.

Poor seasons and poor profitability prospects for wheat-growing caused some concern about farm indebtedness in these areas.

In late 1983, a Parlimentary select committee was appointed to inquire into rural hardship. The State Minister for Agriculture also announced that the Department of Agriculture would conduct a farm survey to determine the …

Improved Catchments For Farm Dams, I A F Laing

Journal of the Department of Agriculture, Western Australia, Series 4

The amounts and frequency of runoff from unimproved farmland catchments in Western Australia's cereal and sheep districts are notoriously variable and unreliable. As a result many farmers have constructed improved catchments to ensure better reliability of farm dams for livestock and homestead water supplies.

Improved catchments which are used extensively on these farms are all of the compacted or bare-earth type. These include roaded catchments, flat batter dams and, to a lesser extent, scraped catchments. This article mainly discusses roaded catchments, the most common of the improved catchment types on farms.

Sandplain Hardpan : A Different Dam Construction Material, A F. Mccrea

Journal of the Department of Agriculture, Western Australia, Series 4

Before 1980, the Department of Agriculture did not believe that suitable farm dam materials could be found in light land soils. However Beacon earthmoving contractor, V> J> Pavlinovich, has demonstrated that where suitable cemented subsoils or 'hardpan' existed, a succcessful dam site could be found.

This material should not be confused with compaction or traffic hardpans ehich are dense layers of soil found near the surface. Traffic hardpans result from compaction of soil materials with the passage of vehicles and farm machinery. Rather, the hardpan referred to here is a natural subsoil layer that has been cemented by silica and …

Drainage Prospects For Saline Wheatbelt Soils, P R. George

Journal of the Department of Agriculture, Western Australia, Series 4

Sub-surface or groundwater drainage by buried tube drains or open ditches can reclaim saltland in the Western Australian wheatbelt. However, this method is expensive and not all sites can be drained cost-effectively. Each drainage site is unique, so careful investigation of each site is essential before recommendations on drainage method and design can be made.

Hillside Seepages, R A. Nulsen

Journal of the Department of Agriculture, Western Australia, Series 4

'Hillside seepage' is a local, descriptive term applied to almost any wet patch occurring out of the valley bottom. Depending on their surface appearances, 'hillside seepages' are described as 'springs', 'soaks', 'wet patches', or seeps.

Whatever they are called, seeps can cause problems. The land in the seep is wet, unworkable and non-productive. If the seep is saline and the water flows downhill, further land is lost from production, bared and subject to erosion. Even small seeps, while not affecting much land, break up a paddock and complicate the working pattern for tillage and harvest.

Draining A Saline Seep, W J. Burdass

Journal of the Department of Agriculture, Western Australia, Series 4

Sub-surface drains have dried out a salty seep on farm land in the Katanning district. Capeweed and clovers are now growing on more than three-quarters of the land that was previously bare or carried only patchy sea barley grass.

The drains are still running water after five years. The salt content of the surface soil has been reduced markedly and the salt content of the effluent water is decreasing.

However, to complete the reclamation, further drains will be necessary. Both existing and any new drains will have to be flushed periodically because blockages of pipes cause problems.

Drought Proofing The Farm : Case Studies, J L. Frith

Journal of the Department of Agriculture, Western Australia, Series 4

For many years, Western Australia's north-eastern wheatbelthas suffered chronic shortages of water for stock and domestic use. The area's averageannual rainfall is generally low - less than 300 millimetres - and droughts in the 1970s caused futher problems. manydams in the area leak or have inadequate catchmentsand groundwater is scarce ormofmpoor quality.

In March 982, the Western Australian Government provided $100 000 for the Department of agriculture to demonstrate the potential of establishing permanent, drought-proof water supplies on farms in the north-eastern wheatbelt. The methods were to use exixting techniques to build dams and catchments. In a year of low …

Underground Water Supplies In The Wheatbelt, T T. Bestow

Journal of the Department of Agriculture, Western Australia, Series 4

Underground water originates from rainfall. The size of the underground recource in any region is broadly related to the amount of rainfall. However, rainfall intensity and seasonal distribution are just as importent as the quality. A relatively small annual fall which consists of a series of heasvy showers or storms close together, may be a more effective source of recharge to underground water than a larger fall that is more evenly distributed over a longer period.

A large annual rainfall, however, is no guarantee that underground water supplies will be readily available. This is because soils and the underlying rocks …

Chemical Sealing Of Earth Dams, R G. Pepper

Journal of the Department of Agriculture, Western Australia, Series 4

Leakage is not a major cause of failure of farm dams in the Western Australian wheatbelt, but it is a problem in some districts where it can limit stock carrying capacity. Leaking dams are especially common in the West midlands, the north-eastern wheatbelt and the 'jarrah-belt' which extends from Bindoon, southward to Manjimup and Mt Barker (see map and Table 1).

Some dams which leaked when first built have sealed themselves over the years. Others have been successfully sealed using sodium tripolyphosphate.

Drainage And The Law, G A. Robertson

Journal of the Department of Agriculture, Western Australia, Series 4

Drainage is being increasingly used in Western Australia as an attempted cure for land salinisation and waterlogging. This is nor surprising as drainage is a technical approach that has, in some cases, improved saline land and reduced the effects of waterlogging. However, drainage is not always successful or cost-effective. A detailed site assessment is required before any large or costly drainage system is attempted. Articles in this issue of the Journal of Agriculture discuss that aspect in detail.