Posted: 05/07/2014 at 12:40
Sounds odd to me too. Beans fix Nitrogen and Kale needs that. Companion planting (there are two definitions of that - one is for pest control and the other is entirely different and is for nutrient sharing) is often used with the oldest known one being "3 sisters" where you plant sweetcorn (need N and provides natural 'poles' for the beans), climbing beans (fix N) and squash (living mulch to reduce weeds and shade roots) all together in the same place, usually a mound.
I've done it many times and it does work.
The only negative concerns crop rotation. This is important to prevent pest and disease build-up in the soil. I found this to be more important in the long run so no longer use the nutrient-sharing type of companion planting except with sweetcorn when I always plant beans with them as they can be trained to support the corn by intertwining between stems, completely eliminating the need for poles and string.
Lots of experimenting has been done in my garden over many years - can you tell?