The best way to get the maximum seed yield per plant is to give them plenty of space. Provided that the soil is fertile & the plants are in full sun, pole beans should give you an increase of 200/1 minimum. I generally get at least 300/1 with wide spacing. Mulch is vital for me to get that number, especially under hot dry conditions... not sure if it would be as helpful your climate.

Hopefully, that will be enough seed for your purposes, with no further action required on your part. If not, there is one trick that might increase the yield even more... but personally, I would do this only as a last resort.

Normally, as has been often mentioned on this forum, conventional wisdom recommends against fertilizing beans with nitrogen. It tends to result in lush growth, but few and/or later beans. It is the most frequent cause of the "why no beans" threads.

But used carefully, a little N can increase bean yield. Many years ago, when I lived in SoCal, I had access to large amounts of composted horse manure & used to manure my whole garden in Spring before tilling. The beans would grow a lot of vine before flowering; but fortunately for me, the manure broke down halfway through the season, and I still had plenty of season left. Excess nitrogen locks the beans into a growth cycle until the nitrogen level drops, so you get a lot of growth. If the nitrogen levels are too high, and take too long to get used up, you can get a lot of growth - with beans optional.

So if you choose to use this method, I would recommend a single application of a moderately low-N, water-based fertilizer, applied when the plants begin to vine. Hopefully this will keep the plants in their vegetative (growth) stage long enough for the vines to have developed more leaf & added vigor prior to flowering - which would allow them to support a larger pod load. The delay in flowering should not be a problem in your climate, unless the delay would put them in harm's way during the period when seed is ripening.

Keep in mind that with all of that extra growth, you will need to give the plants extra space to grow into. If that is not possible, I would not recommend applying fertilizer.

I don't what effect the fertilizer would have, if applied after the reproductive phase has already begun. It's possible that if the fertilizer were applied later - when the pods are drying & the leaves have begun to drop - it might shock the plant into re-entering the growth phase. I have used this technique in the past to boost a second crop from bush beans. I'm not sure what impact (if any) that the extra N would have on the quality & longevity of the seed, which is the reason I recommend to use this technique only as a last resort.

Thanks so much Chris! I have each pole spaced at one foot and the vines are looking a lot happier than they did last year at the four inch spacing. I have access to manure, but the soil is pretty fertile already so I'm most likely not going to amend it. I will be getting some straw though for mulch!

zeedman, what is the maximum spacing for pole beans if you have all the room in the world?
6",12",18" or 24" in the row & 16" or 24" between rows, so one can lean into the raised bed to pick the inside row, without stepping on the bed?
At 16" one can get 3 rows out of each bed, at 24" one can get 2 rows out of each bed. Or do you recommend not using raised beds, but fertile soil in standard rows.
At 200 - 300 to one I will plant anyway you say works.
With mulch, should one use a soaker hose to get even watering?

Jolj, I will answer your questions on your Bean Chart thread, so as to not hijack this one.