Watering & Fertilizing Beans
Beans need about one inch of water a week for good growth. If your garden doesn't get sufficient rain, you must water. Watering is probably the most critical summer gardening chore for many people, and it's the job most often done wrong.
Seven Watering Fundamentals
1) Avoid frequent, light waterings. That's the biggest mistake people make. They think splashing a little water on the beans will make them happy, just as a wake-up splash refreshes us. The reverse is true for plants. Water beans deeply but gently to a depth of four to six inches. Thorough soaking encourages the roots to seek water deep in the soil. With a deep root system, the plants can survive hot, dry weather a lot better.
2) Don't water by the calendar, but rather when the plants need it. Check the appearance of the plants, the condition of the soil on the surface and the condition four to five inches down. Plants will often look wilted on a hot afternoon - that's okay; they'll probably perk up overnight. If the plants look wilted in the morning, they need watering.
3) A good mulch will save water, protect the soil from the sun's scorching heat, keep the root area of the plants cooler and reduce evaporation.
4) Water early in the day if you sprinkle or hose from above. That allows plenty of time for the leaves to dry. If the leaves are wet overnight, diseases can quickly invade the plants.
5) With furrow irrigation, drip irrigation or soaker hoses, which all deliver water at the soil surface and not on the leaves, you can water in the late afternoon, evening or even at night.
6) Try to avoid watering during the middle of the day because evaporation losses are usually highest then.
7) Don't overwater. The soil, while anchoring the plant, also acts like a sponge. It can only hold so much water. Learn the water-holding capacity of your soil, so you don't waste precious water or smother the roots of your plants.
However, if you haven't had rain for a week or two, water. Where it's hotter, you may have to water more often than that if you don't have rain. After a while you'll get so you know just by looking at your plants whether your garden needs water or not.
As mentioned earlier, beans are "light feeders." They don't require much fertilizer. It's easy to give them just about all the nutrients they'll need by mixing a light dose of fertilizer into the top two to three inches of soil on planting day or the day before. Three to four pounds of commercial fertilizer such as 5-10-10 per 100 square feet is sufficient for most garden soils, or use the equivalent amount of nonchemical fertilizers, such as well-rotted manure, compost, bonemeal and cottonseed meal.
Fertilizing by the Numbers
The numbers on the fertilizer bags indicate by weight what percentages of each of the three most important nutrients - nitrogen (N), phosphorus (P) and potassium (K) - are present in the mixture. Although the percentages may vary, the order is always the same: N, P and K. For instance, 5-10-10, which is good for beans, indicates the fertilizer contains 5% nitrogen, 10% phosphorus and 10% potassium. Nitrogen promotes healthy green leaves and stems, and you don't need much of it for beans. If you have too much, the plant will spend more time making leaves and less time making beans. Phosphorus promotes strong roots and potassium conditions the whole plant, helping it to bear fruit and resist disease.