| Abstract: | Uptake of nitrogen from the subsoil (30–200 cm) by winter wheat has been measured in field experiments on deep loess-parabrown soils in northern Germany and at Rothamsted (England) for different crop rotations and manuring schemes. The results can be summarised as follows: - 1 The mineral nitrogen content of the subsoil varies widely depending on farming practice.
- 2 The effective depth limit for N uptake by winter wheat appears to be 150 cm.
- 3 Averaged over 22 sites, 33% of the total N uptake was from the subsoil (range 9–75%); 25% was from the 30–90 cm soil layer and 8% from the 90–150 cm soil layer.
- 4 Decreasing the N supply to the topsoil increased N uptake from the subsoil.
- 5 N uptake from the subsoil is not dependent on water uptake from the subsoil; nitrate is readily transported to absorbing roots by diffusion.
- 6 When deciding on the rate of fertilizer N to apply in early spring, soil mineral N to a depth of 90 cm should be taken into account. For subsequent dressings, the soil mineral N between 90–150 cm depth needs to be considered.
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