The total yields of sweet clover per acre for the season are usually less than those of alfalfa except in the semiarid unirrigated portions of the country. Sweet clover ordinarily yields more to the acre than any of the true clovers.

When the seed is sown in the spring in the North without a nurse crop, yields of 1 to 3 tons of hay of good quality may be expected the following autumn, The Massachusetts Agricultural Experiment Station obtained 2,700 pounds of hay per acre in the fall from spring seeding, while the United States Department of Agriculture obtained 3,000 pounds of hay per acre in August from May seeding in Maryland. Yields of 1 to 2 tons, and occasionally 3 tons, have been obtained in Michigan, Illinois, Iowa, Kansas, the Dakotas, and other States. In Illinois, Iowa, and Kansas yields of 1 to 1¹/₂ tons are often obtained after grain harvest when weather conditions are favorable.

The first crop the second season yields 1¹/₂ to 3 tons of hay to the acre in the northern and western sections of the United States. The second crop of the second season will yield from three-fourths to 1¹/₂ tons to the acre, although this crop usually is cut for seed.

When sweet clover is seeded in the South without a nurse crop on fairly fertile soil that is not acid, three cuttings of hay, averaging at least a ton to the cutting, may be secured the year of seeding. When the seed is sown in the early spring on winter grain, two cuttings, yielding at least 1 ton to the cutting, may be obtained. The first crop the second season yields on an average 1¹/₂ to 3 tons of hay to the acre. In 1903 the Alabama Canebrake Station obtained 2¹/₂ tons of hay after oat harvest and a total yield of 3 tons per acre from the same field in 1904.

TIME TO CUT SWEET CLOVER FOR HAY.

The first season's growth of sweet clover does not usually get coarse and woody and therefore may be cut when it shows its maximum growth in the fall, In regions where more than one crop may be obtained the first season, the first crop should be cut when the plants have made about a 30-inch growth.

The proper time to cut the first crop the second season will vary considerably in different localities, depending very much upon the rainfall, the temperature, and the fertility of the soil. In no event should the plants be permitted to show flower buds or to become woody. In the semiarid sections of the country sweet clover does not grow as rapidly as in more humid regions. Neither do the plants grow as rapidly on poor soils as upon fertile soils. In the drier sections the best results usually are obtained by cutting the first crop when the plants have made a growth of 24 to 30 inches. On fertile, well-limed soils in many sections of the country a very rapid growth is made in the spring, and often the plants will not show flower buds until they are about 5 feet high. On such soils it is very essential that the first crop be cut when the plants have made no more growth than 30 to 32 inches if hay is desired which is not stemmy and if a second growth is to be expected.

HEIGHT OF STUBBLE TO BE LEFT WHEN CUTTING FOR HAY.

It is not necessary to leave more than an ordinary stubble when cutting the sweet-clover hay crop in the fall of the year of seeding. A stubble 4 or 6 inches in height, however, will serve to hold drifting snow and undoubtedly will be of some help in protecting the plants from winter injury. While sweet clover without question is more hardy than red clover, usually more or less winterkilling occurs, and any protection which may be afforded during cold weather will be of considerable benefit.

While the first crop in the second year comes from the crown buds, the new branches which produce the second crop of the second year come from the buds formed in the axils of the leaves on the lower portions of the stalks which constitute the first crop, as shown in figure 4. These branches usually commence growth when the plants are about 24 inches high. In fields where the stand is heavy and where the lower portions of the plants are densely shaded, these shoots are soon killed from lack of necessary light. (Figs. 4 and 5.) The branches which are first to appear and which are first to be killed are those closest to the ground. It is therefore very important when cutting this crop to cut the plants high enough from the ground to leave on the stubble a sufficient number of buds and young branches to produce a second crop.

Examination of hundreds of acres of sweet clover in different sections of the United States during the summers of 1915 and 1916 showed that the stand on at least 50 per cent of the fields was partly or entirely killed by cutting the first crop the second season too close to the ground. A direct relation exists between the thickness of the stand, the height of the plants, and the height at which the stubble should be cut if a second crop is to be harvested. It is very essential to examine the fields carefully before mowing, so as to determine the height at which the plants should be cut in order to leave at least one healthy bud or young branch on each stub. In fact, the stand should be cut several inches above the young shoots or buds, the stubble may die back from 1 to 3 inches if the plants are cut during damp or rainy weather.

When fields of sweet clover contain only a medium-heavy stand and when the plants have made no more than a 30-inch growth, a 5 to 6 inch stubble usually will be sufficient to insure a second crop, but where fields contain heavy stands—15 to 25 plants to the square foot—it may be necessary to leave an 8-inch stubble. In many fields examined in northern Illinois in June, 1916, heavy stands had been permitted to make a growth of 36 to 40 inches before cutting. In a number of these fields a very large percentage of the plants were killed when an 8 to 12 inch stubble was left. (See fig. 5.) A careful examination of such fields showed that the young branches had started on the lower portions of the stalks and had died from lack of light before cutting. In semiarid regions, where the plants do not make as rapid growth as in humid sections, they may, as a rule, be clipped somewhat closer to the ground without injury.

On account of the difference in the growth that sweet clover makes on different types of soil and on account of the difference in the thickness of the stand obtained in different fields, it is impossible to give any definite rule as to the proper height to cut the first crop.

MOWER CHANGES FOR CUTTING SWEET CLOVER.

It is good practice to replace the shoe soles of the mower with higher adjustable soles, so that a stubble up to 12 inches in height may be left when cutting sweet clover, Shoe soles such as are shown in figures 6 and 7 may be made on any farm provided with a blacksmith's forge, or they can be made at any blacksmith shop at a cost which should not exceed $2.50. Preferably they should be of strap iron, about one-fourth of an inch thick and 2 inches wide; however, old pieces of iron or steel which may be found on the farm will serve the purpose.

Then these soles are to be placed on machines that have shoes of the type used on the Deering mower, the forward 8 inches of the sole for the inner shoe should be tapered gradually to a blunt point and bent in such a manner that it will hook into the slot in the shoe. (Fig. 6, C.) When the soles are to be placed on mowers having shoes of the type used on McCormick machines, the forward 8 inches of the sole for the inner shoe should be tapered gradually to about 1 inch in width, bent forward so that it will fit against that portion of the shoe where it is to be bolted, and have a hole of the proper size bored for the bolt three-fourths of an inch from the end. (Fig.6, B and D.) The bottom of the sole should be rounded, so as to run smoothly on the ground when the cutter bar is raised to cut at different heights. The back portion of the sole should be upright and should have holes bored in it, so that it may be set for the cutter bar to rest at different heights from the ground. Preferably the lower hole of the upright should be located so that when the bolt in the shoe is run through it the cutter bar will be 6 inches from the ground. It should be long enough to permit four or five holes, 1 inch apart, to be bored above the lower one. (Fig. 6, A.)

With some makes of machines it is not advisable to raise the cutter bar higher than 10 inches from the ground, but when this is true the cutter bar may be tipped upward, so that a 12-inch stubble is left.

The forward end of the shoe sole to be used on the outer shoe should be tapered gradually to 1 inch from the end. The forward inch should be one-fourth of an inch in width and bent slightly upward and inward, so that a hook will be formed to fit into the slot in the front end of the shoe. (Fig. 7, B.) The rest of the sole should curved, so that it will run smoothly on the ground when the cutter bar is set to cut at different heights. The upright which is bolted to the sole should preferably be made of three-eighths by 1 inch material and should have six holes, 1 inch apart, bored in it, so that the outer end of the cutter bar may be raised to the same height as the inner end. On practically all standard makes of mowers the outer shoe sole hooks into the shoe instead of bolting to it, as is the case with the inner sole on some machines. A wheel is used in place of a shoe sole on the outer end of the cutter bar on some machines. When this is the case, the upright to which this wheel is attached should be lengthened. On other machines the forward end of the sole hooks into a slot in the shoe in the same manner as the inner sole. In this event the front end of the sole should be bent slightly upward and outward. (Fig. 7, C.)

Before shoe soles are made for any mower a careful examination should be made of the shoes to determine the exact size required and the manner in which they should be attached to the forward ends of the shoes.

CURING AND HANDLING SWEET-CLOVER HAY.

One of the greatest difficulties in curing sweet clover is the fact that the plants usually are ready to be cut for hay at a time of the year when weather conditions are likely to be unfavorable for haymaking. Little trouble is experienced in curing this crop in the drier sections of the country where the methods used for alfalfa are employed. The curing of sweet clover is more difficult than the curing of either red clover or alfalfa, as the leaves are very apt to shatter before the stems are cured. Every possible means should be employed to save the leaves, as these constitute the best part of the hay. (See Table II.)

Table II.—Average analyses of the leaves of four samples of well-cured white sweet-clover hay.

[Analyses made by the Bureau of Chemistry.]

The hay collected for the above analyses represented the first cutting the second season. The plants had made a 30 to 36 inch growth at the time of cutting. It will be seen that the protein content of the leaves is almost three times as great as that of the stems.

In the drier sections of the country or when the first crop of the year of seeding is cut for hay in the North-Central States the mower may be started in the morning as soon as the dew is off. The hay should remain in the swath until the following day, or until it is well wilted, when it should be raked into small windrows. After remaining in the windrows for a day it may be placed in small cocks to cure. Cocks made from hay which has dried to this stage will not shed water well and therefore should be covered if it is likely to rain. It is important that the cocks be made small enough to be thrown on the rack entire, as many leaves will be lost if it is necessary to tear them apart.

When sweet clover is permitted to dry in the swath, a large percentage of the leaves will be lost in windrowing and loading unless handled with the utmost care. Hay in this condition should never be raked while perfectly dry and brittle, but should be raked into the windrow in the early morning or in the evening, when it is slightly damp from dew. It may then be hauled to the barn or stack after remaining in the windrow for a day.

One of the most successful methods for handling sweet-clover hay, especially in regions where rains are likely to occur at haying time, is to permit the plants to remain in the swath until they are well wilted or just before the leaves begin to cure. The hay should then be raked into windrows and cocked at once (fig. 8). The cocks should be made as high and as narrow as possible, as this will permit better ventilation. In curing, the cocks will shrink from one-third to one-half of their original size. It may take from 10 days to 2 weeks to cure sweet clover by this method, but when well cured all the leaves will be intact and the hay will have an excellent color and aroma. When sweet clover is cocked at this time the leaves will cure flat and in such a manner that the cocks will readily shed water during heavy rains (fig. 9).

When sweet-clover hay is to be stacked it is highly desirable that some sort of foundation be made for the stack, so as to prevent the loss of the hay which otherwise would be on the ground. Several feet of straw or grass are often used for this purpose, but still better is a foundation of rails, posts, or boards placed in such a manner that air may circulate under the stack.

A cover should be provided for the stacks, either in the form of a roof, a canvas, or long green grass. If none of these means is practicable a topping of perfectly green sweet clover will cure with the leaves flat and will turn water nicely.

It is well known that hay made from either red clover or alfalfa will often undergo spontaneous combustion if put into the barn with too much external moisture upon it. No instances of spontaneous combustion in sweet-clover hay have been noted, but this may be due to the fact that comparatively little sweet-clover hay is stored in barns. The same precautions, therefore, should be taken with sweet-clover hay as with red clover or alfalfa.