Fodder Beet Drymatter Sampling

How to take a drymatter sample using the Agricom fodder beet corer.

 

Why do I need to take bulb drymatter samples when weighing my crop? Can't I just use the book values?

Unlike kale crops where many can walk into a paddock and have a fairly good idea of how much yield they have by just looking at it, fodder beet is not so easy, even to the well experienced eye. Bulb drymatter percentages can throw you off completely, in some situations we have seen crop yields halve, just by sending away actual drymatter samples rather than using the book values.

How much variation are we talking?
A couple of years ago, we measured 90 individual bulbs, from the same paddock, the same cultivar, and found the bulb DM% ranged from 11.8% to 20.3%.

Why is there so much variation?
For any given cultivar, drymatter percentages are affected by: Sowing date, sowing rate, bulb size, soil type and fertility, soil preparation, bulb sampling method, regional location and climate - particularly rainfall or lack of.
Coring at least 15-20 bulbs in a row will give you a reliable paddock drymatter percentage, capturing much of the variation.

Agricom’s fodder beet coring tool has been developed as an efficient and more accurate way of obtaining fodder beet bulb drymatter percentages. The corer allows for more bulbs (compared with 2-3 bulbs traditionally sampled) to be taken quickly whilst reducing a large amount of variation that can occur within a paddock caused by factors such as soil type, bulb size, age of crop, the environment and climate.

If the cores are not sampled, stored, or couriered correctly as stated below, the accuracy of the bulb DM% can be largely skewed.


When to take bulb drymatter samples

  • Take bulb drymatter samples at the beginning of the week and overnight courier the samples on the same day. If you can only take the sample at the end of the week or you risk the sample being kept in transit for the weekend, weigh the sample yourself and store in the fridge to be couriered first thing on Monday.
  • It is important to take physical fresh weight yields of the crops on the same day due to the day-to-day variation of drymatter percentage of beet bulbs. If that’s not possible, take as soon as possible to the yielding measurements but avoid if there is a significant rain event in between.

Where to take bulb drymatter samples

  • A quick visual assessment of the paddock is necessary to establish any obvious spatial variation of the crop. If the entire paddock appears fairly uniform (This may be based upon physical fresh weight yields as well), then only one drymatter sample is required in a representative area. If the paddock appears quite variable, it may be necessary to take a separate bulb drymatter sample in those variable areas and/or focus on the getting an accurate measurement in the transition area (As you would with taking yield measurements).

How to take the core sample

  • Once you have picked your sampling area, core 20 consecutive bulbs in a row so as to capture the DM% variation between large and small bulbs. This is considered as ‘one sample’.
  • It is easiest to take a core sample whilst the bulb is still in the ground.
  • Taking the corer, pierce the top ‘shoulder’ of the bulb by moving the leaf out of the way (avoiding coring through the leaf section) and twist and push the corer down on a diagonal angle so as to get a cross section of the bulb.
  • Twist and pull up to remove the bulb core.
  • The core does not have to fill the entire corer cavity but should aim for 10-20 cm in length. Make sure there is no mud or dirt on the core (remove it or retake a core if not possible) and place into a snap lock/airtight bag.
  • Continue up the row to obtain 20 cores to complete the sample.
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