Soil mineral N (Nmin) is estimated from several components.
Nmin is increased by: + Mineral fertilization + Organic fertilization + Mineralization of soil organic matter (humus) + N in irrigation water
Nmin is reduced by: - N intake of the plants - Unavoidable N losses and N-fixation in soil organic matter (immobilization)
The graphic shows a simple example: Two mineral fertilizer applications of 140 kg N / ha each (red line) initially increase Nmin in 0 to 60 cm (pink). By the N uptake of the plants (green) and the immobilization (gray) Nmin decreases again. After the end of the cauliflower crop, Nmin increases through the N mineralization of humus (black) and crop residues (green). In October, Nmin increase only slightly, as the mineralization of crop residues is completed and the mineralization of humus – due to the low soil temperatures – is low.
Plants can only pick up N from the soil layers they have reached with the roots. Therefore, both the temporal course of the root growth and the maximum rooting depth is taken into account, for example 30 cm for lettuce, 60 cm for cauliflower, 90 cm for Brussels sprouts.Entering a Nmin analysis result overrides the estimate for the soil sample day. Thereafter, the estimate is continued based on the analysis result.
Attention : The estimate is based on very simple estimation techniques. The estimates may therefore differ significantly from reality. The fertilizer requirement should therefore not be determined on the basis of an estimated value but, if possible, on the basis of an Nmin measured value.
To create the graphic , in the tab Reports > N-Fluxes select the year, then after clicking on Filter , select which components to display and then click on Create .
- Nmin Estimate Starting Values in the tab Farm Data > Nmin estimates
- Humus N mineralization in the tab Farm Data > Fields.
Soil temperatures also affect N mineralization. Soil temperatures can be set in the tab Farm Data > Soil temperatures .