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worked out. Usually the water has an abundance of potash, a partial supply of nitrogen for the crop requirement, and scarcely any phosphoric acid. The Louisiana Station suggests the possibility of applying nitrogen and phosphorus in high grade commercial fertilizers in small quantities continuously to the water at the flood gates. Stable manure can be used judiciously upon places where surface soil has been removed in leveling
Plat showing method of irrigating rice plantation in South Atlantic States. Heavy black lines represent levees about six feet high, thirty-five feet wide at bottom and twelve feet wide at top. Main canal reaches from river to creek between two levees. Double lines around each tract represent marginal canals or face ditches about three feet wide and deep, and single lines represent field ditches about fifty feet apart. Water enters and leaves each tract through the same flume by means of a box, called a trunk, so arranged that it can be set to allow the water to enter at high tide or can be set to allow water to leave at low tide. (After Keeney.)
the land; but heavy applications are to be avoided upon good soil, lest it cause the rice to lodge. If the straw and hulls are returned to the land the fertilizing ingredients removed are comparatively small. Here, as elsewhere, the economy of fertilizers is a local question, and no specific rules can be given. (117)
510. Laying Out the Plantation.—In preparing a plantation for rice culture, the area must be laid off into fields and a levee or dike thrown up around them. On at least one side of each field there must run a canal or sub-canal. These fields vary in shape and size according to the topography of the land and the ability to bring water to it. Usually the fields range in size from ten to forty acres. These fields are now subdivided into smaller areas, in order to get the water over the whole area with some uniformity. It is at this point that the system followed in the South Atlantic States differs radically from that of the South Central States. In the former the fields are subdivided by ditches placed parallel, usually about fifty feet apart, through which the water is conveyed to and from the land. In the South Central States the fields are divided into sub-fields or cuts, this being done by throwing up field or cut levees along the contour lines twelve to eighteen inches high. To flood the field, water is turned into the highest cut and conveyed from there to the next highest cut, and so on until the field has all been flooded. A drainage ditch at the long part of the field removes the water. The main features of the two systems are shown in the illustrations on pages 362 and 363.
It is important that each of the smallest units of land be as level as possible, so that the water can be kept at as uniform depth as may be over the whole area, since uniformity of depth of water is a prime factor in the growth and maturity of the crop. To obtain the best result, there should not be a variation of more than six inches in the depth of water.
511. Water Supply.—In the South Atlantic States the lands chiefly used for rice culture are the deltas near tidewater. Land is selected so that it may be flooded from the river at high tide and drained at low tide; and is sufficiently remote from the sea to be free from salt water. Rice may be grown in slightly brackish water, but salt water is disastrous. Usually the land is not less than fifteen nor more than thirty miles from the sea. A tide of four feet is sufficient and less is sometimes used. Where properly located, water in this region is ample. Along the Mississippi River the water was formerly supplied from the river by putting a pipe through the levee, the land being highest next the river and the drainage being away from the stream. The water is now conveyed over the levee by means of a siphon, the former method being prohibited by law because the majority of disastrous breaks in the levees was attributed to them. In southwestern Louisiana and southeastern Texas not only are streams used for irrigation but advantage is taken of a stratum of water that underlies this territory at a depth of 125 to 200 feet. When tapped, this water rises near the surface, sometimes within twenty feet, and in a few instances flowing wells have been obtained. Whatever the source of water, it is pumped to raise it to the proper level. The individual planter may have his own pumping outfit or water may be furnished an extensive area from a single system, and the planter is charged a certain percentage (usually one-fifth) of the rice raised for water supplied, or a certain number of pounds of rough rice (usually two barrels, or 324 pounds).
Water for irrigation purposes should be uniform in temperature, not too cold, free from noxious weed seeds and injurious salts.
512. Amount of Water Required.—The amount of water required will vary with many conditions, including evaporation, seepage, drainage and the rainfall. Where abundant and obtained by gravity, larger quantities are likely to be used than where it is pumped. The Louisiana Station says that in that State each acre of rice is assumed to receive the equivalent of one-half inch of water daily during ninety days; this is forty-five inches. Deducting twenty inches for rainfall leaves twenty-five inches to be supplied by irrigation.1
The Office of Experiment Stations has measured the water used at two plantations where water is obtained by pumping, with the following results :2
1 La. Bui. 77, p. 382.
» 0. E. S. Bui. 113, pp. 22-28.
III. CULTURAL METHODS.
513. Preparation of Seed Bed.—Two methods of preparing the soil are followed, known as dry culture and wet culture. In the former the land is plowed in the fall and winter, preferably soon after the former crop has been harvested. In wet culture, the land is flooded in the spring, plowed and seed sown and harrowed in the water, after which the water is withdrawn to permit the rice to germinate. Wet culture is commonly practiced upon the buckshot soil because of the difficulty of plowing it when it is dry. Plowing is usually shallow, sometimes not more than three inches deep. Machinery and the animals drawing it usually sink to the depth of the plowed land; thus deep plowing adds to the labor, especially in the prairie regions where modern harvesting machinery is used. Whatever the customary depth of plowing, it is considered dangerous to plow deeper because of the accumulation of alkali in the subsoil just below the plow line. It is said, however, that where such deeper plowing is done, the alkali may in a measure be washed out by flooding and draining immediately after plowing.
514. Sowing. — The date of sowing may vary from the middle of March to the middle of May. Where dry culture is practiced the sowing is earlier than with wet culture. On the alluvial lands of the Mississippi River the seed is sown broadcast by hand, but on the prairie soils seeding with the ordinary grain drill (135) is preferred because of the saving of seed and uniformity of germination. (131) The rotary broadcast seeder, however, is frequently used. (412) In the South Atlantic States the land is laid off with a trenching hoe into small furrows two to three inches deep, three to five inches wide and twelve to fifteen inches apart. Into these drill rows the seed is deposited and covered lightly, or more rarely left uncovered, in which case the seeds are sometimes soaked in thick clay water to prevent seed from floating away. The rate of seeding varies from one to three bushels per acre of rough rice. In the South Atlantic States two and one-half to three bushels are customary, while in the South Central States one to two bushels are ordinarily used. In new fields or in fields not infested with red rice, if any such exist, great care should be taken to use seed that is absolutely free from it.
515. Application of Water.—When lack of moisture makes it necessary, the land is flooded immediately after seeding for a few days to sprout the seed, when the water is removed. The land is then left until the plants are well started. In the South Central States flooding usually occurs when plants are six to ten inches high, which is from one to two months after seeding. The water remains on the land continuously until the grains are in the milk, when it is removed for the crop to ripen, which requires about a week. The period of irrigation varies from two to three months, usually about seventy days. Flooding usually takes place in June and the water is removed in August. The depth of water used varies, particularly with the supply. A uniform covering of three to six inches is considered satisfactory, although six to twelve inches are recommended. The water is constantly renewed in order to keep it from becoming stagnant, particularly to prevent the growth of weeds which are more abundant in stagnant water. The method