513. Preparation of Seed Bed.-Two methods of preparing the soil are followed, known as dry culture and wet culIn 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culture, the land is flooded in the spring, plowed and seed sown and harrowed in the water, after which the water is withdrawn to permit the rice to germinate.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

of irrigation in the South Atlantic States is somewhat different and is about as follows: As soon as the seed is sown water is let on for four to six days until the grain has sprouted and then withdrawn. This is called "sprout water." After the rice has two leaves, enough water is put on to completely cover the plant, then lowered to about six inches, where it is held for twenty or thirty days, after which it is removed and the field allowed to dry. This is called "stretch water" or "long point flow." The field now remains without irrigation until the plant begins to throw up its culms, the land in the meantime being cultivated two or three times. Water is then turned on and remains on continuously, although changed every week to avoid becoming stagnant, until it is removed for harvest. This last irrigation is known as the "harvest water" or "lay by flow."

516. Drainage. The drainage is effected chiefly through open ditches, generally rather shallow, but the main ditches should be three feet deep in order to remove more effectively the alkali, which in rice lands, as elsewhere where irrigation is practiced, is apt to become troublesome. Rice is rather resistant to alkali, however, so much so that it is sometimes employed for the purpose of helping to rid the land of alkali for other crops. Tile drainage is the most effective method of removing the alkali, but is usually not resorted to on account of the expense and in some cases would not be feasible on account of filling with sediment.

517. Cultivation.-Where the rice has been sown broadcast or by means of a grain drill, no cultivation is practicable. The worst weeds, however, are often removed by passing through the field and pulling by hand. In the South Atlantic States, however, the land is cultivated by hoeing lightly, or, more rarely, by using a one-horse cultivator. This is usually done before the plants begin to joint, the water having been removed and the land allowed to dry for this purpose. (515)

IV. ENEMIES.

518. Weeds.--Perhaps the most serious menace to rice culture is the growth of weeds. This is especially true where rice is grown without cultivation, and where the water comes from streams which abound in weed seeds and readily disseminate them.

Dodson gives the following list of weeds which have proven most menacing to the rice fields: 1

(1) Red rice (Oryza sativa var, rufipogon).

(2) Large indigo, straight indigo, coffee weed, senna, long podded sesban (Sesban macrocarpa Muhl.).

(3) Curly indigo, sensitive joint vetch (Aeschynomene virginica (L.) B. S. P.). (4) Tadpole grass, wiggle-tail, spear grass (Rhynchospora corniculata A. Gray) (5) Bull grass (Panicum agrostidiforme Lam).

(6) Smart weeds (Polygonum, especially P. acre H. B. K.).

(7) Turtle back (Commelina virginica L.).

(8) Alligator head (Diodia teres Walt. and Diodia virginiana L.).

(9) Bird's eye (Scleria-several species).

(10) Morning glory (Ipomoea tamnifolia).

(11) Water grass (Paspalum fluitans Kunth. and P. virgatum)

(12) Moss weeds.

By far the most important and most serious one of these weeds is red rice. (505) Few rice fields are free from it. By many planters red rice is believed to result from volunteer plants growing from seeds of the cultivated white rice. It seems, however, to be demonstrated that it is a distinct strain, and that red rice can be obtained only from the seed of red rice. The two types readily cross, and the results of the Louisiana Station indicate that the red rice has the greater influence where crossing takes place. 2

Next to red rice in importance is the large indigo weed, both because of its abundance and large size, the plant often growing to a height of fifteen feet, while the stems sometimes attain a diameter of two to three inches. Like the curly indigo, it is a leguminous plant.

The alluvial lands are especially liable to become infested with weeds, so that as a rule after two or three successive crops are raised, the soil must be devoted to a cultivated crop or allowed to grow up with weeds for one or two years. The weeds that are injurious to the rice plant are water weeds. If the land is drained, the field will grow up to dry land weeds and largely exterminate the water weeds, when the field can again be cultivated in rice. This is considered by some to be good practice, since the land retains its fertility and the finest crop of rice is the first crop

1 La. Bul. 61, 2d ser., pp. 402-436.

La. Bul. 50, 2d ser.

after such treatment. One of the reasons for flooding is to prevent the growth of weeds, but those which germinate quickly are enabled to keep even or ahead of the rice and thus escape injury from flooding. In some cases, where the weeds get ahead of the rice, especially those weeds (not grasses) which grow from the tip, the fields are mown, which checks the weeds, while the rice, but little injured, shoots ahead, when the field can be flooded and weeds killed. This is not effective for weeds of the grass family, because the habits of growth are the same as in the rice. Mowing stubble and burning it soon after rice has been harvested is a rather effective method of killing weeds; but the exposure of the bare soil to the rays of the sun and the lack of vegetation bring about physical, chemical and biological conditions that are undesirable. Mowing and burning late in the fall, after weeds have gone to seed, is, therefore, more commonly practiced, but is not so effective in destroying weeds, since the moist soil protects many from burning. This late burning is sometimes followed by early spring plowing to induce germination of weeds, when they may be destroyed by cultivation before seeding. This results in late seeding,

A

B

which is objectionable. (514) In the alluvial lands the weeds are pulled by hand two or three times during the growth of the crop.

519. FUNGOUS DISEASES.- The rice plant is sometimes attacked by a smut (Tilletia corona Serib.), occurring on several grasses. It is very similar to the stinking smut on wheat. While not definitely proven, it is believed that the treatment recommended for stinking smut on wheat would be efficacious. (149) The smut has not been widely reported, but in some instances it has apparently done considerable damage. The kernel of the rice is filled with a mass of black spores, as in the case of wheat, but it is not usually abnormally large. The cause of blast or blight, a premature death of the plant or only the head, is not fully understood.

Three spikelets of rice; outer glumes shown at base. A, normal mature spikelet with healthy grain enclosed; B, grain affected with rice smut shown at e; C, grain more completely destroyed with rice smut shown at e. (After Anderson.)

520. INSECT ENEMIES.-The number of insects attacking rice are not many, nor are their injuries extensive or ordinarily serious. The principal one is the water weevil (Lissorhoptrus simplex Say). The adult is a small gray beetle, which makes its appearance in April and May and feeds upon the leaves of the young rice plant. The insects soon breed, and being semiaquatic in habit, the female lays its eggs among the roots of the plant. The eggs hatch in July and August into white, legless grubs, which feed upon the roots of the plant, where the principal damage is done, and which may be detected by the yellowish appearance of the plants, often in clumps. The presence of water seems necessary to the larvae; hence the removal of the water and drying the land at the proper time is recommended, although this practice is injurious to the rice.

The rice grub (Chalepus trochypygus Burm.) is a scarabaeid beetle, the larva of which feeds upon the roots of upland rice. Water kills it.