does phosphorus and potassium help butterbeans fill out?
Certified GKH Gardening Expert
Yes it does! Make sure not to fertilize with any nitrogen at all, though. They "make" their own. This article will give you more information on butterbeans:https://www.gardeningknowhow.com/edible/vegetables/beans/growing-butter-beans-in-your-garden.htm
Butterbeans, aka lima beans are a cool season crop in the South. They don't like temps over 90F. They require 1-2 inches of water weekly. pH is important in butterbean growth. Ideal pH is 5.8-6.5 although 7.0 is acceptable. When pH is out of whack, plants have trouble absorbing nutrients. You need a soil test to know whether adding additional phos and potassium will help. I'm attaching an article that shows how much P, K to add depending on soil test results. You'll see that how much to add varies greatly with your baseline numbers. You are aiming for phos and potassium in high normal range. Going above normal is detrimental to yields.