National Paddock Survey Project

Protocol for soil samplingpre-sowing and post-harvest + installing a rain gauge

Soil Sampling

Each paddock has 2 Zones (Zone A and Zone B).Soil sampling will need to take place along the pre-determined transectin each Zone. Each transect is 200 m long and located diagonally across the sowing direction (covering at least three sowing widths)and will have five Monitoring Points, approximately 50m apart. With a GPS,record latitude and longitudeat each monitoring point (record lat x long in decimals). You will be coming back to this transect for the next four years – accuracy in recording the lat x long is essential.

Soil sampling: Pre-sowing

The survey paddock should be sampled before sowing (preferably during the 6 week period pre-sowing). Separate soil samples are required for (a) soil moisture content and chemical analysis, and (b) Predicta B for soil borne pathogens.

Post-harvest

The transects in the survey paddock should be sampled as soon after harvest as possible – the primary aim of the post-harvest soil sampling is to obtain a finishing soil water – this will close the water balance between starting soil water, crop water use, in-crop rainfall and finishing soil water.

1a Pre-sowingand Post-harvest – soil water and chemical analysis

  • Label four buckets – one for each depth (photo 1)
  • Cut a length of 6 inch PVC pipe in half and clearly mark the above sampling depths (photo 2)
  • With a permanent marker mark the auger tube at 1m depth (photo 3)
  • At the first location (start of the monitoring transect) take five 0-10cm depth samples with a simple foot push sampler (photo 4) and place each sample in the bucket labelled 0 – 10 cm
  • Directly underneath the augerdig down 10cm with a spade and clear a small area (we do this to avoid topsoil falling down the tube during sampling) (see photo 5)
  • Place a ruler or similar on top of the soil where you have dug down to 10cm - auger down to 1m (level to the ruler – see photo 6)
  • Pull the auger out and remove the soil from the auger into the marked halfPVC pipe (photo 7)
  • Cut the soil core in half, length ways (photo 8) and discard one of the halves
  • Place the remaining half of the core, for each depth, into the allocated bucket
  • Repeat this procedure at each of the five monitoring sites along the transect
  • When you have completed the fifth sample, mix the soil in the bucket thoroughly (mixing is critical) – you will need two samples:
  1. Put 200 to 250g of soil in a paper bag, weigh the sample in the field (including the bag) and record the weight on the label (we will send you labels)
  2. Put 150 to 200g of soil in a self-sealing plastic bag (provided by the laboratory)
  • Clearly label all bags:
    > date
    > farmers name
    > paddock name
    > your name
    > Zone A or Zone B
    > soil sampling depth (ie. 0-10, 10-40, 40-70, or 70-100)
  • Keep cool in an esky or cooler bag – never in direct sunlight

1b. Pre-sowing PredictaB sampling

For each transect, at each of the five monitoring points, collect additional topsoil for Predicta B analysis. Use the push probe (see photo 4 above) for collecting the 0 to 10cm depth samples.

  • At each monitoring point take 10 push coresin the row of a previous cereal crop (if visible). At each monitoring point include a piece of cereal stubble (crown to 1st node) if present. Place the soil from each push core into a bucket
  • When you have completed taking all five monitoring points thoroughly mix the soil in the bucket and fill the PredictaB sample bag to between 450 to 500g.
  • Clearly label the bag:
    > date
    > farmers name
    > paddock name
    > your name
    > Zone A or Zone B

/ Photo 1
Clearly label four buckets with the sampling depth (0 – 10, 10 – 40, 40- 70, 70 – 100)
/ Photo 2
Label PVC pipe for separating soil samples
/ Photo 3
Mark the soil auger tube at 1m
/ Photo 4
Taking 0 – 10cm samples with push probe. Place the soil, each time you collect a sample, into a bucket.
/ Photo 5
Directly underneath the hydraulic auger dig down to 10cm and clear soil away
/ Photo 6
Place a ruler or similar across the top of the soil so when pushing the auger down you can easily see when you reach 1m depth
/ Photo 7
Remove soil from auger gently into half PVC pipe (starting at 10cm)
/ Photo 8
With a knife cut the soil core in half length way, throw away one half and place the other half in the appropriate bucket for the depth.

Installing a Permanent Rain Gauge

Close to where you have placed the e-button temperature logger you will need to install a permanent rain-gauge. The permanent rain gauge will be extremely useful for calibrating the paddock rainfall to the nearest BoM stations.

Procedure

  • Set up the rain gauge during at the same time as pre-sowing soil sampling
  • Cut a length of 1.5m PVC pipe (slightly smaller diameter than your soil auger core)
  • Seal one end of the PVC pipe (for example with a bung)
  • With your soil sampler, auger down to 0.5m depth, remove the soil core.
  • Put the sealed end of the PVC pipe into the hole
  • Fix a funnel to the open end (record the diameter of the funnel)
  • When you are at the paddock for the post-harvest soil sampling, remove the PVC pipe, and measure either the weight (g) or volume (ml) of water in the pipe.
  • Replace the tube with funnel and measure again at pre-sowing soil sampling for the following crop

Photos to come

GRDC: National Paddock Survey project -Soil sampling protocol