Hi Stringfellow
I`m not a particularly methodical person in the experimental sense but I do a fair bit of reading/research. I started off as a traditional gardener and gradually changed due to influence from an old allotment holder who gave me some comfrey roots and made me aware of Henry Doubleday (now Garden Organic) and the Soil Association. I avoid mustard because its a brassica and have tried a range of other crops. Grazing rye is my favourite because; it is easy to grow, gives plenty of bulk, covers ground that might be bare all winter, its easy to save seed, I`ve even made rye bread from it. Alfalfa is the interesting one because, although it is leguminous it is not supposed to fix nitrogen at our latitude yet brassicas seem to thrive after it. Alfalfa is deep rooted, penetrates the subsoil and leaves a legacy of organic material in the ground as well as adding plenty to the compost bin. I lose cropping space with comfrey but it gives so much back it is indispensible. A bit long winded but I hope that answers your question.
Pete