Fertilisation recommendation partly based on N-delivery capacity of soil

The total quantity of nitrogen in the soil (N-total) and the carbon-to-nitrogen (C:N) ratio together form the basis for calculating the nitrogen delivery capacity (NDC) of the soil. The nitrogen fertilisation recommendation is determined by the nitrogen annual application rate (pre-planned amount of nitrogen from fertiliser as well as active nitrogen from organic manure) and the nitrogen delivery capacity of the soil. If the nitrogen annual application rate based on the statutory use standards for grass or arable land is lower than the nitrogen annual application rate based on the NDC, the recommendation may be adjusted.

As stated, the NDC depends on the total N content in the soil, but also on the C:N ratio in the organic matter. Depending on the age of the organic matter, the C:N ratio may change. Old, stable organic matter, as in Peat Colonies soils, has a higher C:N ratio (> 20) than young organic matter on dune sand soils (10-15). As a result, old organic matter delivers less nitrogen than young matter.

When livestock manure is used, young organic matter with a lower C:N ratio (5-15) can be supplied. Compost, especially natural compost, delivers more stable organic matter with a higher C:N ratio. If this type of compost is applied over a number of years, the so-called “original strength” of the soil is increased. Soil nitrogen delivery capacity could then exceed 150 kg N per hectare per year.

Average nitrogen delivery capacity by soil type

Source:

Courtesy: BLGG/Eurofins Agro, 2007 (reviewed/updated 2016).

Sources:
Koopmans, C.J., J. Bokhorst, C. ter Berg en N. van Eekeren (2012). Bodemsignalen. Praktijkgids voor een vruchtbare bodem. Roodbont Uitgeverij, Zutphen. 96 p.
Rottink, A., A. Termorshuizen, A. Reijneveld, P. van Vliet, I. Ketelaar en M. Hermans (2007). De bodem doorgrond. BLGG Oosterbeek. ISBN 978-90-812265-1-6. 96 p. ​