Part 6

Many excellent stands have been obtained by seeding late in the spring, but in most sections seeding at this time is not as certain to produce a good stand as earlier seeding. Late spring seeding may be preferable when the ground is weedy and the clover is to be seeded without nurse crop. Under these circumstances a crop of weeds may be destroyed before seeding.

Very good success has been obtained in the Southern and Central States, and in some of the Northern States, by seeding sweet clover in the late summer or early autumn. When there is sufficient moisture in the soil for germination and when good seed is used, better stands have been obtained by seeding about eight weeks before severe frosts are to be expected than from spring sowing. This is particularly true in regions where late spring droughts or severe summer droughts are likely to occur. Seeding at this time may be done after an early crop has been harvested and when weeds are not likely to be troublesome. Plants from fall seeding mature from 10 days to two weeks later the following season than plants from spring sowing of the same year. The later time of maturing is an advantage, in that the plants will be ready to cut during better haying weather. The root growth is not as large from fall seeding as from spring seeding, and therefore not quite as much humus is added to the soil. Late fall seedings are very likely to be injured from heaving on wet clay soils.

UNHULLED SWEET-CLOVER SEED.

Unhulled sweet-clover seed is sown principally in Kentucky, Alabama, and Mississippi. On the limestone soils of regions, which appear to be naturally adapted to sweet clover, very good results are obtained by using unhulled seed. It is not because southern-grown unhulled seed germinates better than northern-grown unhulled seed that better stands are obtained in the South from it, but it is mainly because southern farmers better understand the somewhat exacting conditions necessary for obtaining a stand with this kind of seed. Unhulled sweet clover contains a large percentage of hard seeds which will not germinate until they have been in the soil for some time and have been subjected to varying temperatures.

Seeding experiments have been conducted at Arlington, Va., where unhulled seed which contained 90 per cent of hard seed was sown during each month of the winter. Good stands were obtained on those plats seeded at the rate of 24 pounds (3 pecks) of seed to the acre during December and January, and fair stands on the plats seeded at this rate in February. Later seedings failed to produce a stand.

A large percentage of the unhulled seed sown in the South is seeded during January and the first part of February. Good stands are seldom obtained from unhulled seed south of the latitude of Washington, D. C., when the seed is sown later than the middle of February.

The use of unhulled seed has usually been attended with failure in the northern portion of the United States, although occasionally good stands have been obtained the following spring from late fall seeding. This failure is in part due to the fact that the seed has been sown in the spring and at a tine when only seed germinating well should be used. When unhulled seed is to be sown north of the latitude of Washington, D. C., it should be sown not later than February 15, and preferably earlier. Observations show that fairly good stands may be obtained by seeding during the winter, but care should be taken not to sow seed earlier than necessary on land which is subject to washing. Farmers should have no trouble in purchasing hulled seed, and therefore it is recommended that only hulled seed which germinates well be sown.

RATE OF SEEDING.

The rate at which sweet clover should be seeded varies with the germination of the seed, the condition of the seed bed, the climatic conditions of the region, and the method of seeding. Throughout the humid sections of the eastern United States sweet clover ordinarily is seeded at the rate of 15 to 20 pounds of hulled seed to the acre. From 12 to 15 pounds should be ample where the seed bed is in good condition and the seed germinates 75 per cent or more. In Illinois, the western North-Central States, the Mountain States, and the Pacific Coast States good stands are generally obtained by sowing 10 to 12 pounds of hulled seed to the acre. In eastern Washington it is claimed that from 5 to 8 pounds to the acre are sufficient for good stands.

When sweet clover is grown under irrigation, 8 to 10 pounds of hulled seed usually are sufficient, and from 2 to 4 pounds per acre are enough when seeded in rows from 2 to 4 feet apart. Of unhulled seed 3 to 6 pecks (24 to 48 pounds) or 20 pounds of hulled seed are usually sown in the South for pasturage or hay. In any region at least 10 pounds more of the unhulled than of hulled seed should be sown to an acre. Unless annual yellow sweet-clover seed is thoroughly cleaned it should be sown at the rate of 25 to 30 pounds to the acre.

METHODS OF SEEDING.

The methods used for seeding red clover or alfalfa in any particular region will be suitable for seeding sweet clover. Good results have been obtained by broadcasting the seed on winter grain in the spring when the ground is in a honeycombed condition. Perhaps a better method is to wait until the ground can be worked and then to broadcast and cover the seed with a harrow or to sow it with a drill. Unhulled seed is usually broadcasted, since it is necessary to sow it before the ground is in condition to be worked. Unless the hulls have been rubbed smooth, some difficulty may be experienced in seeding it evenly with a drill.

When sweet clover is to be sown with spring-seeded grain or when it is to lie sown without a nurse crop it may be drilled in or sown broadcast and covered with a harrow. Better stands are generally obtained with a smaller quantity of seed when it is sown with the drill than when it is broadcasted on honeycombed ground. When the seed is sown at the time the grain is planted, the grass-seeder attachment of the drill commonly is used. In some sections the end-gate seeder is used almost entirely. When the seed is sown by either of these methods it may be seeded alone or mixed with the grain. When only the clover seed is sown with a drill, the alfalfa and clover seed drills are to be preferred.

Sweet-clover seed may be mixed with some inert substance of approximately the same size and weight and sown with an ordinary grain drill. Finely cracked corn, cracked wheat, or coarse bran often are used for this purpose. When one portion of sweet clover is mixed with two portions of a filler find the drill is set to sow one-half bushel of wheat, it will usually sow from 15 to 20 pounds of sweet clover to the acre. As this quantity will vary with the different types of drills, it is necessary to test each drill, so that the seed may be mixed with the filler in such proportions that the desired quantity will be sown. The drill may be tested by blocking it up, so that the geared wheel is off the ground, and this wheel may be turned a sufficient number of times to establish a definite portion of an acre. The seed that runs through can then be weighed and the rate per acre determined. The rate may be determined more accurately by plugging up the grain tubes or by tying a small sack on each tube and pulling the drill for a specific distance over the field to be sown. The jar of the drill will cause it to drop more seed than when it is blocked up and run by hand.

It is often desired to seed sweet clover on land which can not be cultivated. When sown on such land it is recommended that unhulled seed or seed that contains a large percentage of hard seed be used and that it be broadcasted during the winter. The subsequent freezing and thawing will cover many of the seeds and cause them to germinate. It is a good plan to scatter in deep gulleys mature plants that have not shattered all their seed. The branches of these plants will help to hold the seed in place until it germinates and the young plants become established.

Seed may be scattered on native prairie ground in the late winter, but unless it is trampled into the ground by live stock disappointing results are likely to be obtained at first. Fair results have been secured by planting seed with disk drills on prairie sod after it had been double-disked in the early spring. This method should be used in preference to broadcasting the seed and depending on cattle to trample it in. Mr. George Hummer, of Prairie Point, Miss., reports good success in his locality by simply broadcasting 1 peck of unhulled seed on Bermuda-grass sod not later than January 1.

INOCULATION.

Excepting soil acidity, lack of inoculation probably is responsible for more failures with sweet clover than any other one cause. When sweet-clover plants are not inoculated they must depend upon the available nitrogen in the soil for their supply, and as the crop is grown for the most part on soils low in nitrogen the plants can not be expected to make more than a small growth. (Fig. 9.)

Arny and Thatcher, at the Minnesota Agricultural Experiment Station, obtained 10 times as much dry matter in the tops and seven times as much in the roots of sweet-clover plants which had been grown on thoroughly inoculated soil as from plants Which had been grown on soil not inoculated. Moreover, the plants grown on the inoculated soil contained 117 pounds more nitrogen to the acre than those grown on the uninoculated soil.

Experiments in many other sections of the country, and especially in the northeastern quarter of the United States, where but little sweet clover or alfalfa has thus far been grown, show that inoculation is very essential to success. Ordinarily it is not necessary to inoculate sweet clover when it is to be planted on land where alfalfa, bur-clover, or black medic thrives, because the same strain of inoculating germs inoculates all of these plants. However, when this closer is to be planted on land where none of the plants inoculated by this strain of the organism have been grown, inoculation should be provided. In localities where sweet clover or other plants inoculated by the same strain of bacteria thrive, the early growth has at times been made much more vigorous by inoculating the soil or seed thoroughly.

It is not safe to assume that a certain piece of soil is inoculated because any one of the plants inoculated by the same strain of the organism is growing or has been grown on other fields in the same vicinity. Many fields have come under observation where sweet clover was a failure because the plants were not inoculated, when plats or fields of alfalfa growing near by were abundantly inoculated.

There are several methods of inoculating sweet clover, any one of which when properly applied should give good results.

THE SOIL-TRANSFER METHOD.

The soil-transfer method of inoculation consists in scattering over the field to be seeded 200 to 400 pounds to the acre of soil collected from sweet-clover, alfalfa, or bur-clover fields where the healthy plants show an abundance of tubercles on the roots. It is strongly recommended that this soil be scattered on a cloudy day or in the early morning or in the evening and immediately harrowed or disked into the ground, as the sun's rays are very injurious to the inoculating germs. It is a good plan for the person scattering the soil to walk directly in front of the harrow. When this practice is followed little harm can be done by the light. To facilitate even scattering, the soil may be mixed thoroughly with two or three times its weight of other soil, preferably from the field where the sweet clover is to be sown. Soil used for inoculating sweet clover does not necessarily have to be scattered on the land just previous to sowing the seed. It may be scattered a few months or a year in advance of the time the sweet clover is to be seeded and be just as effective as if it were scattered at a later time. In general, where sweet clover is to be seeded in the spring on winter grain, the inoculation should be applied before the grain is sown.

Good success has been obtained by drying in a dark place soil containing the inoculating germs, sifting it, and running it through the fertilizer compartment of a grain drill. When this method is employed it is not necessary to use as much soil as when it is scattered broadcast.

A comparatively new method which has given successful results calls for dampening each bushel of seed and spreading it on a cloth, paper, or cement floor, where half a gallon of throughly inoculated soil from sweet-clover or alfalfa plants may be sifted over it. Some people prefer to add a trace of glue or sugar to water, so that more of the soil will adhere to the seed, although some soil will remain on the seed if the glue or sugar is not used. When only this quantity of soil is used it should be collected from around the roots of sweet-clover plants which are abundantly inoculated. Such soil may be collected in the fall and kept until spring in a cool, dry, dark place with no injury to the inoculating organisms. Seed treated in this manner should be kept in the dark and should be sown as soon as possible after treating.

THE PURE-CULTURE METHOD.

The pure-culture method has the advantage of greater case of transportation and freedom from danger of introducing harmful pests upon the farm. Inoculation by pure cultures may be carried out in either of two ways: