The seed is planted in hills at a depth of 1 to 2 inches. Toward the north, the rows are usually made 4 feet apart and the hills spaced 3 feet apart in the row. Farther south the rows should usually be made about 6 to 8 feet apart. On very light land the hills may be 4 feet apart in the row; on heavier land, 6 to 8 feet apart. As a general rule three seeds are planted to the hill, and not less than two should be planted. One bushel of medium-sized seed should plant from 5 to 6 acres. When the plants are from 4 to 6 inches tall, the weaker ones should be removed, leaving one plant in a hill. The crop is cultivated similar to corn until the plants are large enough to shade the ground. In case the field becomes foul with weeds and grass, some hoeing may be necessary, but practically all the cultivation required can be done with a horse-drawn weeder. Some varieties in which the beans pop out when the hull is fully ripe are known locally as "poppers," and after the beans begin to ripen, the field must be gone over every few days and the ripe beans collected in order to avoid loss. Other varieties tend to retain the beans in the hull after they are ripe. The climate affects the popping of the beans, and a variety which shatters badly in one region may shatter very little when grown in another. In harvesting, a common method is to cut off the spikes with a knife and collect them in large sacks. They are then hauled to a shelter of some kind and allowed to dry until the pods will crush easily. Various methods are used in thrashing castor beans. If the variety grown is one which "pops" or drops its seeds when they are ripe, the spikes are sometimes piled on a hard ground or plank floor fully exposed to the sun and furnished with sides of boards or cloth 6 to 8 feet high to catch the beans as they pop out. In some varieties mere drying does not cause the pods to open, and specially constructed machines have been used to remove the beans from the pods. After the beans have been thrashed or popped out, a fanning mill is used to separate the hulls, chaff, and dirt from the beans, which are then sacked and stored for market. The yield varies greatly and will depend much upon cultural conditions, the season, the variety grown, and the care exercised in harvesting and thrashing the seeds. In Oklahoma the average yield of the popping varieties is said to be 8 to 10 bushels per acre. Yields up to 25 bushels per acre have been reported for favorable conditions. For some years prior to the war the farm price for castor beans was about $1 a bushel. Early in the war the increased demand for castor oil caused a sharp advance in the price of the beans, which has gradually declined. In June, 1920, the wholesale market quotation was about $3 a bushel. The normal market requirement in the United States for castor beans is about 1,000,000 bushels annually, but during the last year of the war nearly 3,000,000 bushels were imported.