And the reason why runner beans can't deal with high nitrogen feeds like chicken manure is because they make their own fertiliser by photosynthesis from the sunlight, and store it in little granules round their roots. When i dug up my first crop of runner beans at the end of the season I was really worried about all these little yellw nodules sticking to the roots - had I got some kind of pest laying nasty eggs? An old hand on the plot showed me how to rub them off into the compost heap as fertiliser granules. What a relief!
