Soil Sampling in Spring

Research by Agriculture Victoria has shown that there are no pasture yield differences whether phosphorus fertiliser is applied in summer or autumn.

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Why not get a head start on fertiliser programs for your grazing customers by initiating some soil testing this spring?

Pasture topdress programs should start with an assessment of soil fertility levels, soil physical limitations and botanical composition of the pasture. They should also recognise the current and anticipated stocking rates.

Soil sampling pastures is the best way to assess current soil nutrient levels and start planning appropriate nutrient strategies for next year.

There are also a number of advantages of soil testing in spring rather than in the heat of summer.

• When you go out and sample in spring, you can easily see any areas that are not representative of the paddock as a whole.
• See and avoid tree lines, soaks, urine patches, cow or sheep manure and stock camps in spring than when pastures are grazed down or dried off in summer.
• The soil is moist from recent rain in most areas and this will make it easy to accurately collect the 0-10cm depth sample.
• Additionally, geo-referencing soil sampling sites is a good idea, as it allows you to return to those sites for future sampling.

From there, with the sampling done and the test results back from the laboratory you can:

• Establish the current nutrient status of the soil to provide the basis for future strategies.
• Indicate if any soil ameliorants are required to correct a soil’s physical and chemical imbalances.
• Determine soil factors that may be limiting pasture production.
• Identify opportunities to improve farm profitability through efficient soil fertility management.
• Determine the best fertiliser types (including blends) and appropriate rates for individual paddocks.
• Monitor the progress of current nutrient strategies and fine-tune inputs.
• Assist in the planning process through improved budgeting of farm financial resources.

By getting on top of the planning in spring and early summer, your customers will be able to take advantage of early topdressing opportunities.

Autumn topdressing is an important time of year for lifting pasture growth before it naturally slows during the cooler months.

For best responses, the appropriate fertiliser product should be applied at the appropriate rate based on soil tests before the autumn break and before sub-clover has germinated.

After the opening rain, phosphorus is then available to germinating subterranean clover. The increased autumn clover growth will directly impact on winter production levels.

The later SuPerfect^® is applied, the lower the winter production from subterranean clover and improved perennial grasses.

In short, you can’t go too early, but you can be too late.

Questions are often asked about movement of phosphorus from fertiliser granules when applied to pasture.

The movement of water-soluble phosphorus from single superphosphate granules into the soil is virtually complete within 24 hours of application even when soil conditions are dry and rainfall does not occur. 

The hygroscopic nature of single superphosphate means moisture is absorbed from the atmosphere and soils even at low moisture contents. (Williams 1969)

An added advantage of SuPerfect^® is that its calcium sulphate component enhances capillary uptake of water from the soil into the fertiliser granule. (Williams 1969)

Even with these advantages, it is still important to follow best practice for SuPerfect fertiliser application to pastures.

• Avoid applying fertiliser when ground cover is less than 70%. (Managed perennial grass based pastures should have these ground cover levels unless severely overgrazed)

• Prevent fertiliser from entering waterways or water storages during application.

• Do not apply fertiliser if heavy rain is forecast within four days.

• Do not apply to waterlogged soils.

• Locate fertiliser storage away from potential run off areas.

So, plan a soil testing program today and get out there sampling and enjoy the spring weather!

For more information, feel free to contact me on 0427 006 047 or jim.laycock@incitecpivot.com.au.

Jim Laycock
Technical Agronomist – temperate farming systems
Incitec Pivot Fertilisers