The first requisite of soil is thorough drainage; the second is a moderate amount of organic matter. Some varieties of beans will grow and mature light crops in poor soils, but high fertility is essential to large yields.
Beans are grown successfully in all types of soils. This is especially true of the dwarf garden varieties. Some of the best early crops are grown on distinctly sandy soils, while satisfactory yields are common on sandy loams. The light sandy soils are especially important for lima beans. Gravelly loams frequently produce excellent crops, but require a large amount of humus. Clay loams are unquestionably the best for the field class of dry beans, and there seems to be a consensus of opinion that all varieties representing this group have a preference for limestone soils. When early maturity is an important factor, sandy soils or sandy loams with southern aspects are most valuable. Muck soils are not satisfactory, because they produce an excessive growth of plant and a meager crop of beans.
Fig. 59. Beans Intercropped With Strawberries At Norfolk, Virginia.
In New York and Michigan the field varieties are usually grown in a three-year rotation - clover, beans and wheat. A heavy inverted clover sod provides the best conditions for a large yield. The Michigan Station recommends a four-year rotation, in which case alsike clover and timothy seed should be mixed with red clover, so the land can be pastured for one season. Corn is often used in a four-year rotation, when the order of cropping is clover, corn, beans and wheat. In trucking and market gardening, the garden varieties may be worked into the system of cropping at almost any point, provided there is a sufficient time for the beans to attain marketable size. As this crop must not be started until the ground is thoroughly warm, there is often opportunity to grow early spring crops, such as lettuce and radishes, before planting beans. In the trucking sections of the South, snap beans are often planted after kale or spinach, and the beans are removed in ample time for starting fall crops.
Early spring plowing is especially important when sod land is to be used. The soil should then be harrowed several times before planting to destroy weeds and to conserve moisture.
It is generally conceded that the mineral elements are of greatest importance in the growing of beans. This is unquestionably true with the field class and late-maturing varieties which have the entire season to provide themselves with nitrogen from the atmosphere. In the districts where dry beans are grown extensively, it is seldom that more than 2 per cent of nitrogen is used in the fertilizer. Many farmers omit this element altogether. Some producers of field beans apply six to eight tons of stable manure an acre and the mineral elements are used quite freely.
In trucking and market gardening, fertilizers are generally employed that contain high percentages of the three elements. Voorhees ("Fertilizers," p. 269) suggests 500 to 600 pounds an acre of a 4-8-10 mixture, supplementing if necessary with 20 to 30 pounds of phosphoric acid and 60 to 75 pounds of potash. While potash is regarded essential, experiments in Mississippi show that the addition of kainit lowered rather than increased the yield of snap beans. The same station recommends 125 pounds of cottonseed meal (or its equivalent), 62.5 pounds of nitrate of soda and 250 pounds of acid phosphate an acre. The Georgia Station secured the highest yield of Valentine beans by applying 400 pounds of acid phosphate, 100 pounds of nitrate of soda and 100 pounds of muriate of potash. Several experiment stations have found potash highly beneficial, while phosphoric acid has made the best showing in tests made at most institutions. Unless the soil requirements are definitely known, the only safe course is to apply a complete fertilizer carrying a fair percentage of each element.
Various methods are used in the application of fertilizers for beans. Drilling or broadcasting after plowing is the most common plan. Fertilizer is often applied along the rows with side distributing machines. Hill applications of manure as well as fertilizers are frequently made for pole beans.
The selection of high-grade seeds is significant. When a small quantity is to be saved, pods may be chosen from the most vigorous and the most productive plants. It is especially important to avoid anthracnose by intelligent seed selection (317). Nearly all the beans sold for seed purposes by American seedsmen are grown in this country. The prices paid the growers for seed beans of most dwarf varieties vary from $1.30 to $2.50 a bushel. Seedsmen base their contract prices on a yield of 8 to 12 bushels an acre, while much larger yields are often secured (315). Nearly all the seed lima beans are grown in California; prices range from $2.75 to $4.00 a bushel.
Early planting is not recommended for any of the varieties of field beans. The objections are: (1) There is danger of the seeds rotting before germinating; (2) if the plants appear too soon frost may catch them; (3) early plantings are more likely to rust than later plantings; (4) cold, wet weather may stunt the plants, cause an uneven start and consequently a lack of uniform maturity. It is always better to wait until the ground is thoroughly warm and when there is little danger of damaging weather conditions. The kidney group may be planted the earliest, followed by the marrows and then the pea varieties. In New York the kidneys may be planted the latter part of May, and the pea varieties from June 5 to 20.
Spacing distances between rows range from 24 to 34 inches, 28 being most popular. Some investigators believe the largest yields are obtained when the beans are 4 to 6 inches apart, while the usual distance is from 2 to 4.