Optimal soil sampling depth

The results of soil analysis are only as reliable as the quality of the soil samples taken in the field. An important component of the quality of soil samples is a constant depth of sampling. Because all soil test calibration studies and fertiliser recommendations for non-mobile nutrients (e.g. phosphorus, potassium, zinc) are based on a soil sampling depth of 0 to 20 cm, which is determined by the historical depth of tillage. If you take soil samples that are too shallow or too deep, you can distort the results of the soil analysis and the resulting fertiliser recommendations. Getting the most accurate and useful fertiliser recommendations starts with a good quality soil sample.

Typically, Agrotest takes samples at a depth of 20-28 cm. But if the client has been working with the No-till system for more than 5 years, we analyse the soil at a depth of 15 cm.

Most farmers work with mini-till, and sampling to a depth of 30 cm is relevant for this system.

If we consider sampling from a depth of 60-90 cm to determine mobile sulphates and nitrates, such analysis is not appropriate in routine practice, only for spot experiments to adjust the nutrition system and technology or for scientific research.