Getting the best from your soil sample
The most effective time to take soil samples is just following harvest of the last ratoon of the previous crop cycle. This allows time for any fertiliser and lime requirements to be applied during the fallow. An exception to this is where fallow legume crops are going to be planted. Soil testing can then be completed in late crop cycle ratoons so as to indicate fertiliser and lime requirements such as sub optimal soil pH. This can then be corrected prior to establishment of the fallow legume.
Once you have identified blocks being planted to sugarcane then representative blocks should be chosen from these areas. The key to choosing representative blocks is to identify sample areas that have similar characteristics such as soil type, fertiliser and lime and mill by-product application history, productivity, irrigation and use of fallow crops. As a general guide a block defined as the same soil type can be where the soil type represents more than ¾ of the total block area. If there is more than one soil type in a representative block then more than one soil sample should be taken representing each soil type.
In respect to Reef Regulations if you farm commercial sugarcane in the Burdekin Dry Topics, Mackay Whitsunday or Wet Tropics regions you will need to soil test blocks prior to planting. Representative blocks should not represent areas larger than 60 hectares (148 acres) in size. Where the representative block is larger than 5 hectares (12 acres) then sample within a 5 hectare area which best represents the total area.
Essentially you will get the most value from your sample when the area it represents varies the least.
How do I sample for soil analysis?
Select sites to take soil cores from. The cores should be representative of the whole area, taken in a grid or cluster pattern. Some possible grid patterns for cane blocks are shown below. Where possible, the use of GPS is recommended to identify sampling points so that samples are taken from similar points the next time soil testing is required.
Avoid areas where large amounts of mill by-products have been dumped and with unusually high or low fertility spots. Best practice recommends samples should be taken from the shoulder of the cane row (approximately mid way between centre of cane row and the centre of the inter row). This should avoid sampling of compacted areas in the inter row or pieces of stool within the cane row.
Make sure each core is taken at the appropriate depth of 20cm. This is best done with a soil auger, which can be hired or purchased through your CANEGROWERS local office. (Conditions differ for Tableland members please call 07 4092 6065). Do not use augers or shovels made from galvanized iron otherwise zinc contamination could occur.
Take a minimum of 10 individual cores for each sample. The more cores in the sample the better representation of your block.
If the determination of nitrate/ammonium nitrogen is required then an initial air drying of the soil (by spreading the sample out on clean plastic sheet and dry in direct sunlight) is recommended to reduce biological activity.
The cores can be collected into the sample bags provided. If preferred, or the sample size is too large, they can be collected into a clean plastic bucket and after air-drying and thorough mixing, a sub sample taken and transferred to the sample bags provided.
Securely close each sample in a sample bag and label clearly.
Fill in the submission form and shipment airway bill and put the samples plus the submission form in the pre-paid courier bag. Send the samples to ARL immediately or store in the fridge until they can be sent.
Call our Customer Centre on 1800 624 122 to discuss your testing requirements.