Part 2

CONTENTS.

Page.

Introduction 3

Species of sweet clover 4 White sweet clover 5 Biennial yellow sweet clover 8 Annual yellow sweet clover 9 Other species of sweet clover 9

History 10

Distribution 10

Climatic adaptations 12

Requirements for obtaining a stand 12 Soils suitable for sweet clover 13 Resistance to alkali 13 Need of lime on acid soils 14 Fertilizers 17 Use of a nurse crop 18 Choice of seed 19 Preparation of the seed bed 21

Seeding 22 Hulled sweet-clover seed 23 Unhulled sweet-clover seed 24 Rate of seeding 25 Methods of seeding 25

Inoculation 27 The soil-transfer method 28 The pure-culture method 29

Treatment of the stand 30 Treatment the first season 30 Treatment the second season 32

Sweet clover in mixtures 32

Eradication of sweet clover 33

INTRODUCTION.

Sweet clover is an important forage crop in many regions. Although one of the oldest of known plants, not until very recently has it been considered seriously as a forage plant in this country. The principal causes for not utilizing this crop were its aggressiveness on uncultivated land in many localities, the tendency of the stems to become woody as they mature, and the refusal of stock to eat sweet clover before they had become accustomed to the bitter taste. Another reason was the fact that until recently red clover could be grown in the eastern half of the United States without difficulty. In northern Kentucky the continuous growing of tobacco or of tobacco and wheat impoverished the soil to such an extent that crops no longer could be grown successfully. Upon the abandoned farms in this section sweet clover was introduced as a honey plant. Owing to the remarkable yields of tobacco that were obtained on such farms after sweet clover had been grown for a few years the acreage of this plant increased very rapidly. For a number of years sweet clover has been grown on the Selma chalk (rotten-limestone) soils of Alabama and Mississippi as a soil-improving crop. At the present time it is being cultivated in practically every State, and the acreage is increasing very rapidly.

After it had been demonstrated that sweet clover would grow successfully on soils too depleted for other crops, many experiments were conducted to determine its value as forage. It was found that it was not only a valuable soil-improving crop, but that it made an excellent pasture and hay plant, quite palatable and rich in protein.

White sweet clover comprises a very large percentage of the acreage seeded to sweet clover at the present time. On this account this species ordinarily is referred to simply as "sweat clover." The yellow biennial species is designated as yellow sweet clover, and the annual yellow species as bitter clover, sour clover, or annual yellow sweet clover. This usage has been adopted in this bulletin.

The cultivation of sweet clover should be preceded by a thorough understanding of the requirements for obtaining a stand. It can not be grown successfully on all soils, as many assume from seeing it growing in uncultivated places. Neither will it thrive in many sections of the country without careful preparation of the seed bed. Sweet clover will not grow successfully in acid soils unless lime is applied, but it will make a good growth in soils too low in humus to grow red clover, provided the soil is neutral or alkaline.

Sweet clover is an excellent plant to precede alfalfa, as the large roots do much toward breaking up and aerating the subsoil. Contrary to the belief of many, it will not inoculate the soil for alfalfa unless inoculation is applied to the sweet clover. If, however, the soil contains but few inoculating germs, the sweet clover will serve as a medium to inoculate it thoroughly.

SPECIES OF SWEET CLOVER.

A number of species of sweet clover are found throughout the world, and most of them are native to temperate Europe and Asia as far east as Tibet.

White sweet clover, yellow biennial sweet clover, and yellow annual sweet clover are the only species which have given sufficient promise as forage and green-manure crops in this country to warrant growing them under cultivation.

Melilotus alba Dear.

Melilotus officinalis (L.) Lam.

Melilotus indica (L.) All.

It is difficult for the average person to distinguish between the different species of sweet clover from an examination of the seeds or seed pods only. The differences are indicated in figure 1. Where there is a question as to the identity of a sample of seed it should be sent to a State agricultural experiment station or to one of the seed laboratories of the United States Department of Agriculture for identification.

WHITE SWEET CLOVER.

White sweet clover (fig. 2) is ordinarily referred to as melilotus or meliot in the South and merely as sweet clover in other portions of the country. When soil conditions are favorable for germination, sweet-clover seedlings will appear from one to two weeks after seeding. On account of the biennial nature of the plants, they do not seem to make much growth above ground the first month or six weeks after germination, but during this time they are developing root systems rapidly and thus becoming established, so to be able to withstand adverse conditions. Plants which have made no more than 2 inches of top growth very often have produced roots 6 inches or more in length (fig. 3). The tap-root continues to develop rapidly throughout the growing season the first year, and by autumn often reaches a length of 24 to 36 inches and a diameter of three-fourths to 1 inch at the crown.