Nitrogen Fertilization for Peas: BNF, Zero N Bedarfswert, and Rotation Benefits
Grain peas (Körnererbsen, Pisum sativum) are an important protein crop in German crop rotations, valued both for their own grain yield and for the nitrogen and break crop benefits they provide to subsequent cereals. Like all grain legumes, peas have a fundamental nitrogen management philosophy that differs from arable crops: the DüV 2020 Anlage 4 assigns a Bedarfswert of zero kg N/ha for grain peas — meaning they require no mineral nitrogen input.
Biological Nitrogen Fixation
Peas form an effective symbiosis with native Rhizobium leguminosarum strains present in most German agricultural soils. Peoples et al. (2009, Field Crops Research) reported that 65–75% of pea nitrogen comes from atmospheric fixation under European field conditions. A 4 t/ha pea crop (containing approximately 130–160 kg N/ha in above-ground biomass) derives 85–120 kg of this from BNF.
The Soil N Inhibition Effect
Jensen et al. (2012, Plant and Soil) demonstrated that soil Nmin values above 40 kg N/ha significantly inhibit nodulation in peas. This is the key agronomic constraint: fields with high residual soil N (from previous heavy N application, late-season slurry, or high mineralization) will support poor BNF and nutrient-deficient crops. Managing peas after heavily fertilized previous crops or on high-N soils carries real risk.
Starter N: A Limited Case
A minimal starter dose (0–20 kg N/ha) is occasionally used on soils where Nmin is very low and early seedling growth is at risk before nodule establishment (3–4 weeks). However, given the inhibition effect documented by Jensen et al., starter N should only be applied when Nmin is genuinely below 20 kg N/ha and early-season growth is at risk.
Vegetable Peas (Gemüseerbsen)
A different standard applies to fresh-market vegetable peas, where DüV Anlage 4 sets a Bedarfswert of 85 kg N/ha due to the earlier, lower-BNF harvest stage. This article focuses on grain peas only.
Rotation Nitrogen Credit
Grain peas leave 20–40 kg N/ha residue credit for the following winter cereal, primarily from root and stem residues. This should be accounted for in the following crop's N planning.
Conclusion
Grain peas require zero mineral nitrogen when grown on soils with good rhizobium activity. The management priority is ensuring high BNF by avoiding high-Nmin fields and not applying mineral N that would suppress nodulation.
Plan your rotation N budget including pea credits: Open the NRate Calculator