Fig. 213.—A field of Biloxi soy beans growing on typical rice soil in southwestern Louisiana. This field has béen so thoroughly cultivated that there are no weeds in it
SOY-Bean Rotation Increases Rice Yields Greatly
Crop rotation has not been a factor in developing the rice industry in southwestern Louisiana. The pasturing of rice fields after several years of cropping has been the only recognition of the principle of crop succession in this section. Experience has shown that this method is not effective in controlling weeds, especially red rice, the worst weed of the southern rice field. Red rice seed may remain viable in the soil for at least four years and will germinate only when brought near the surface by plowing and other tillage operations.
Experiments conducted for a period of 14 years at the rice experiment station, Crowley, La., show that weeds can be controlled and may be eradicated by growing rice in rotation with soy beans. The success of weed control depends upon thorough cultivation. Cultivation that permits weeds to produce seed is not effective. Tillage that is necessary to prepare land for soy beans also aids greatly in reducing weeds. The land should be plowed during the previous winter to a depth of at least 5 inches and disked several times in spring before seeding. By repeated light diskings several germinations of red rice may be obtained and destroyed before the soy beans are sown.
Experiments and the experience of rice farmers who are using this rotation indicate that the Biloxi is better adapted to rice field conditions than any other variety of soy beans that has been tested. (Fig. 213.) This variety should be sown in rows 4 feet apart at the rate of 30 pounds per acre. Seeding may be done with an ordinary corn planter adjusted to drop one or two seeds from 2 to 4 inches apart in the row. The seed should be sown just beneath the soil surface. Deeper seeding is likely to result in a poor stand. Sow not earlier than the last week in May and preferably not later than June 15. Thus sown, the plants are relatively short and bear short limbs that fruit rather heavily. Such plants are easily cultivated and can be harvested with machinery without appreciable loss. Early seeding has little effect on date of maturity, which with the Biloxi normally occurs in early November.
Cultivation should begin as soon as the plants can be readily traced in the row. It may be done with a riding cultivator. By using the disk and other attachments alternately this implement will keep the soil in a condition that will promote the germination of red rice and other weed seeds, the growth from which can be easily killed by later tillage. Cultivation should be frequent and continue as long as weed growth is noticeable.
Weed control is not the only advantage of the soy-bean rotation. Plowing under the soybean plants after the beans are harvested adds to the soil a large quantity of organic matter which decomposes rapidly when drainage is good. The upturned soil under these conditions readily responds to tillage in preparing a suitable seed bed for rice. Good seed-bed preparation insures a more thorough destruction of weeds, better germination, a better stand, a stronger root growth, and larger yield. When the soil is deficient in organic matter such a seed bed is not easily obtained even with extra tillage. Soil fertility also is greatly increased by the decomposed vegetable matter. On the typical rice soil of Louisiana the soy-bean rotation is giving an average acre increase of 10 bushels of a better grade of rice, which is a greater return than is being obtained by the use of commercial fertilizers.