Aged manure or organic compost is the ideal garden fertilizer. It will not "burn" tender young bean stalks. The fertilizer is slowly released over time, this prevents growth spurts that develop leaf growth but do not promote bean development. Green beans are not called green because of their color. Also known as snap beans or string beans, green beans are called "green" because they are picked early in the season, before they reach full maturity. Beans may be yellow, green, purple or mottled in any combination of white, yellow, green and purple shades.
Gardeners who raise worms know the proven benefits of worm castings on plant growth. Georgia Red Wiggler worms multiply quickly and produce nutrient-rich casting and liquid that promotes vigorous growth. Organic and toxin free, worm castings should be worked into the soil prior to cultivation or lightly sprinkled on the soil at the base of growing bean plants. Starter worms and worm kits can be purchased online or from home and garden centers.
A balanced commercial fertilizer blend that specifies it is 10-10-10 on the label is a useful fertilizer to work into the soil prior to planting. Read package directions carefully prior to application. A small amount of a balanced mix of nitrogen, potassium and phosphorous can be applied without damaging the plant. It is very easy to "burn" bean plants with aggressive fertilizer application. If in doubt, do not fertilize. Most garden soil has sufficient nutrients to grow beans without the risk of plant damage by fertilizer applications.
Regions that experience water shortages are wise to harvest grey water to irrigate vegetable crops, including green beans. Grey water is household water that does not contain sewage. Dish water, shower water and laundry water can be collected and applied to the garden. Be sure to only use products that do not contain salts or chemicals. The grey water will have a very small fertilizing effect. Dish water will contain small particles of food that will provide nutrients as they decompose.