At the end of the season, where my runner/french beans are concerned, I cut down the plants, then roughly chop them and bury them in the ground, leaving the roots in. They will be well rotted by the following year. When I completely dig over the plot in November/December, I throw on loads of chicken pellets and bfb, and then leave it. Then when Spring arrives, I rotivate the whole plot ready for planting.
Also, in winter, because my plot is on the acid side, I throw on lime, but not where I will be planting the spuds.