Chair of Plant Nutrition

Soil sampling

When?

  • Soil samples are taken shortly before fertilizer application

Tools

  • Soil auger plus scraper
  • Spade can be used down to 30 cm soil depth
  • Tray
  • Bags
  • Labels (plus pen)
  • Sieve (mesh size about 1 cm)
  • Cooling box with cooling elements

Soil sampling

  • Soil samples are collected from the rooting depth of the crop (0-30 cm for shallow rooted crops plus 30-60 cm and 60-90 cm for deeper rooted crops)
  • Push the auger into the soil, twist 2-3 times und pull out the auger from the soil while twisting again
  • Scratch out the soil from the auger and collect the soil into a tray
  • Collect at least ten soil samples representing the entire field

Homogenization

  • Mix composited soil samples thoroughly
  • Passing through a sieve of about 10 mm mesh size allows for a good homogenization
  • Discarded particles (e.g. stones) should be accounted for in the calculation of the N-amount (see section calculation)

Soil water content determination

If the soil is not dry, the soil water content should be assessed and accounted for in the calculation of the N-amount (see calculation), either by:

  • oven-drying or air-drying (using subsamples)
  • soil water content estimates
  • using appropriate water content sensors in the field

A simplified on-site determination of the soil water content is described in the reference section.

Storage of soil samples

  • Store soil samples if measurements are carried out later (packed in a labelled bag containing field name, soil depth and date)
  • Keep soil samples cool (about 4°C), if measurements are delayed
  • Freeze soil and defreeze soil samples again before processing if measurements are done at a later date