Nitrogen Fertilization for Persian Clover: Reliable BNF and Cover Crop Value
Persian clover (Perserklee, Trifolium resupinatum) is an annual legume cover crop that has gained popularity in German farming systems as an alternative to Alexandrian clover (T. alexandrinum), particularly on heavier, moisture-retentive soils where T. resupinatum's tolerance for wet conditions gives it an agronomic advantage.
BNF Performance in German Soils
The key differentiator of Persian clover from a nitrogen management perspective is its nodulation reliability. Schmidtke (2015) and Peoples et al. (2009, Field Crops Research 111) documented that T. resupinatum has more robust nodulation under cool, wet German growing conditions than T. alexandrinum. %Ndfa (nitrogen derived from atmosphere) typically reaches 75–92% in established stands.
BNF potential is estimated at 100–200 kg N/ha over the growing season — at the upper end of annual cover crop legumes. This higher BNF, combined with better establishment reliability on heavier soils, makes Persian clover an attractive N-contributing cover crop.
Mineral N Requirements: Essentially None
Given the high %Ndfa and reliable nodulation, Persian clover has no meaningful mineral nitrogen requirement. The DüV standard demand for pure legume stands is 0 kg N/ha. Unlike Alexandrian clover, the nodulation lag is less pronounced and consistent, meaning even the limited starter N case that applies to T. alexandrinum is rarely justified for T. resupinatum.
This simplifies management: sow, inoculate seed if the field has not grown Persian clover before, and allow BNF to supply the crop's N needs.
Higher Biomass Yield Than Alexandrian Clover
Persian clover tends to outyield T. alexandrinum in German trials — figures of around 20–25% higher yield are reported in some sources (e.g. LfL Bayern IB 1 2022), though results vary by site and season, with a typical fresh weight yield of ~30 t/ha (DM ~18%). This higher biomass means a potentially larger N contribution to the following crop through green manure incorporation.
Cover Crop Role and Following Crop Credit
Persian clover as a summer cover crop (following winter cereals, harvested in July) can reach harvest-ready biomass by September–October. Incorporation provides 30–70 kg N/ha equivalent to the following winter cereal.
Conclusion
Persian clover is the preferred annual legume cover crop on heavier German soils. Its management is straightforward — no mineral N required — and its BNF contribution to rotation nitrogen budgets is among the highest of annual legumes.
Include cover crop N credits in your rotation planning: Open the NRate Calculator