just for reference:
In his book “Comfrey, Past Present and Future” Hills listed the results of analysis of Comfrey grown at Bocking.
Comparative Nutritional Analysis of comfrey, compost and manure
Material Water % N% P % K % C:N
Farm Yard Manure 76.0 0.64 0.23 0.32 14:1
Wilted Russian Comfrey 75.0 0.74 0.24 1.19 9.8:1
Indoor Compost 76.0 0.50 0.27 0.81 10:1
He also made Comfrey juice by using 14lbs of comfrey leaves in a 20 gallon drum. Again the results of the analysis are shown below.
Material DM N P K
Tomorite 0.1410 0.0130 0.0139 0.0093
Comfrey 0.4090 0.0140 0.0340 0.0059
DM – dry matter, N – Nitrogen, P – Potash, K – Phosphorous