Wamuran Co-op customers have available to them a professional soil testing and analysis service which has been a boon to many of the farmers and growers in the area.

Increased plant nutrition by the use of both synthetic and organic fertilizers has arguably increased crop yields, and hence profitability, more than any other single agricultural practice. Attempting to calculate the correct amount of fertilizer to provide adequate nutrient availability can be a difficult, if not impossible, task.

This is because one of the most important factors in nutrient uptake and usage is the amount of moisture that will be available to the crop, since most nutrients used by plants are absorbed in solution form.

The amount of fertilizer required will also be influenced by the potential or expected yield, nutrient uptake efficiency, mineralisation, soil bulk density and existing soil nutrient levels.

Applying large amounts of fertilizer which is not going to be needed by a crop, or on the other hand, not having enough fertilizer to maximise profitability through increased yield, is not an efficient practice.

A better practice would be to establish a paddock’s nutrient needs before fertilizer is applied. This can easily be achieved by having your soil tested through the Wamuran Co-op at Incitec’s laboratory.

There are several major links in the chain of events which lead to the effective fertilizer recommendations using soil analysis.

These links include:

Soil sampling and analysis is a valuable systems tool, providing insight into the nutrient and general fertility status of surface and sub-surface soil layers.

Farmers and growers will usually have a soil analysis performed for one of four reasons:

1. To determine the reason for poor growth (trouble shooting),

2. To assess the suitability of current management practices over time,

3. To adjust existing fertilizer and management programs so as to ensure optimum yield potential is not limited to soil nutrient status,

4. To predict the behaviour of the crop later in the season and perhaps in the following seasons.

The end result, and usually the prime objective, is to arrive at a fertilizer recommendation tailored to the individual requirements of each production system.

If a sample is taken from a large area (say 50 or more hectares), it is often advisable to take more than 40 cores to make up one sample. Many of the problems with soil testing are often traced back to errors made when the sample was taken.

Staff at the Co-op will assist you with information about how and from where to take your soil samples. There are some areas where you should not take samples:

• Avoid unusual areas such as stock camps, dam sites, within 10 cm of current and old fence lines, timber burns, headlands and poorly drained areas.

• Avoid areas of poor growth or excessively good growth such as dung and urine patches in crops or pastures.

• Avoid areas of differing soil type, drainage patterns, fertilizer usage and cut and fill areas.

In most situations, it is the topsoil which is of most interest when soil sampling. The topsoil is defined as the most recently formed soil, containing organic matter (humus) and is of highest nutritional value to plants. It is very often this layer of soil in which the fibrous feeding roots of most crops are located.

Topsoil sampling depth varies depending on the crop grown, but generally ranges from 0 to 25 cm. Information about the suggested depths for individual crops is available from the Co-op.

As most fertilizers are applied to the soil surface, or incorporated into the topsoil by cultivation, it is likely that the topsoil has the greatest fluctuation of nutrient status throughout the crop’s growing season.

For crops such as deep rooted perennial tree crops and perennial pastures, it is often an advantage to sample the sub-surface to identify any nutrient levels which are either toxic or deficient.

Deep sub-surface sampling is common for cotton and cereal crops to measure the nitrate nitrogen status of the profile. Sub-surface sampling is also used in pasture and annual horticultural row crops when investigating areas susceptible to salinity or soil acidity and where structural problems may limit plant growth.

The time of soil sampling will depend on a number of factors; the following are general guidelines:

• In rain grown or dry land cereal and pasture situations, soil sampling is usually best performed after the opening rains.

• For horticultural row crops, soil sampling is required several weeks prior to planting, unless there is a likely requirement for lime or gypsum. Under these circumstances sampling is required 2 to 3 months prior to planting to enable enough time for effective soil amelioration.

 

For horticultural tree crops soil sampling is generally required in late winter or early spring. Sub-surface samples are also recommended at this time.

For sites where the establishment of tree and row crops or long term pasture is intended, soil analysis is recommended several months prior to planting to enable lime and gypsum time to have the greatest effect throughout the soil profile.

Once a sample has been collected, the main objective should be to get it to the Co-op as soon as possible so we can on-forward it to the laboratory. It needs to reach the laboratory in a condition as close as possible to that when it was collected.

Soil samples are best kept in plastic bags, but because most samples contain moisture, microbial activity will continue while suitable temperatures prevail. Therefore, bearing in mind the warm nature of our prevailing climate, it is recommended that bagged soil samples be transferred to an esky or cool box containing cooler bricks as soon after sampling as possible.

Samples should never be left in their bags in the sun or in the back of a ute, hot car or other similar places for extended periods. The chances of biologically-induced changes to the chemical properties of the soil are reduced if this advice is heeded.

When the results of your soil tests are returned to the Co-op (usually within 5-6 working days) our qualified staff prepare the written interpretation. This involves the assessment of each result and a determination of the nutrient rate required for top production.

In the interpretation we need to consider the field information given us by the grower, the location of the field and any climatic peculiarities along with the crop or plant being grown. In addition the grower’s own goals, management skills, farm equipment and financial situation must be taken into account.

Remember, the results are applicable only for the current situation. As soils are dynamic systems, the levels of plant available nutrients can change with the season, cultivation, plant growth and management practices.

The final stage is the conversion of the nutrient needs into a fertilizer or soil amendment recommendation. This involves the determination of the rates of the nutrients needed at the various growth stages or times of applications. Then follows the finding of the most suitable fertilizer or amendment to apply to correct the situation.

We always encourage our customers to be involved in the interpretation and recommendation stages. The final recommendation for each situation will be given to you in writing and will give the frequency, timing and placement of application, the product name recommended and the suggested rate of application.

A soil test through the Wamuran Co-op will cost you $88 (This price includes GST).