Deep roots of Brassica oleracea have high uptake of 15N-nitrate to 2 meters soil depth

Summary

• Deep roots may be important for uptake of NO3- by annual crops. A field experiment with the deep rooted crop curly kale (Brassica oleracea L. convar. acephala (DC.) Alef. var. sabellica L.) was performed to investigate root distribution and N uptake in deep soil layers.
• Root distribution was investigated by use of minirhizotrons and root extractions to 2.4 m depth. The capacity for crop N uptake was studied by deep 15NO3- placement followed by analysis of plant 15N content after 3-30 days.
• The atom percent 15N excess (APE) of plant samples was of similar size after uptake of 15N placed at depths in the range of 0.4-2 m. Root colonisation and start of 15N uptake were synchronized in 2.4 m depth.
• The deep roots had higher inflow of 15N compared to the more shallow roots. Root depth was more important for the ability for NO3- uptake than root abundance. Thus deep roots can be important for N uptake and for reduction of NO3-¬ leaching from annual cropping systems.