Soil sampling for sugar cane

Soil fertility can change as a result of nutrient inputs, removal in produce, loss mechanisms and fixation. The extraordinary wet conditions in many sugar cane areas over the past months is likely to have resulted in nitrogen loss by denitrification and leaching.

Soil fertility can change as a result of nutrient inputs, removal in produce, loss mechanisms and fixation.

The extraordinary wet conditions in many sugar cane areas over the past months is likely to have resulted in nitrogen loss by denitrification and leaching.

Soil testing will be particularly important to help growers answer questions such as:

  • what has happened to nutrient levels where soil has been removed or deposited?
  • has the rain led to leaching or denitrification?
  • has the rain resulted in increased mineralisation of plant available nutrients?

There is no one single answer to these questions. Soil testing on a block by block approach is needed to identify soil nutrient reserves.

This will show how much the soil has available to contribute to the next sugar cane crop and help identify the fertilisers needed to fulfil the crop’s nutritional requirements.

Testing can also help farmers avoid over and under application of fertilisers to improve productivity and minimise the potential for inefficiencies.

There are three key aspects to successful soil testing to determine the soil’s fertility status and the requirement for fertilisers.

These are sampling, analysis and interpretation. Each component is equally important to the accuracy of the entire process.

The key to soil sampling is to ensure that the sample taken is representative of the block concerned. This is generally done by taking a sufficiently large number of soil cores (usually 25 or more), so that the result of an analysis does not change greatly if another set of samples were to be taken from the same area.

Ideally, samples should be taken at least three months prior to planting, especially if it is likely that lime, gypsum or dolomite will be required. Once collected, the samples should be kept cool and despatched to the laboratory as soon as possible.

When choosing a laboratory to analyse soil samples, growers also need to ensure that the analytical procedures used are best suited to measuring the plant available nutrient status of the soil and are the accepted industry methods.

Incitec Pivot Fertilisers’ Nutrient Advantage® Laboratory Services is both NATA accredited and ASPAC certified and has a long history of providing high quality soil and plant analysis to sugar cane growers, industry and research bodies.

Cane growers can choose from three soil analysis packages from Nutrient Advantage Laboratory Services – Basic, Standard and Complete. Each test complies with Reef Regulation requirements.

Consider using the Complete test to ensure your adviser is fully aware of any potential issues. This test includes analysis of nitrate nitrogen, chloride and trace elements, along with phosphorus, potassium, sulphur, silicon, exchangeable cations, organic carbon and pH.

While less comprehensive soil testing may be less expensive, this could mean that not all analyses are being done and you may be missing out on important nutritional information.

Local knowledge is also important because the recommendation should take into account factors such as site characteristics (topography, drainage, and soil depth), availability of irrigation, irrigation water quality, yield expectation, the local fertiliser application techniques and preferred application equipment.

The end result, and perhaps the prime objective of soil testing, is to arrive at a nutrient recommendation that is tailored to the specific requirements of individual blocks to benefit sugar cane productivity.