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The garden beet (Beta vulgaris) although a biennial is grown as an annual. It is one of the most important of the root crops. Beets are hardy and easily grown and are found not only in a large percentage of market gardens but also in nearly all home gardens. During the first season of growth it accumulates a large amount of food in the fleshy taproot. If the beet is grown a second year, most of the surplus food is used in the production of aerial shoots. These are much branched and leafy and reach a height of 2 to 4 feet. The "beet" itself is largely the fleshy upper portion of a long taproot. The upper part or crown is a very much shortened, fleshy stem, upon the apex of which the leaves are borne. The root proper may be distinguished from the stem or crown by the two opposite, longitudinal rows of secondary roots (Fig. 21).
Beet seeds of the Edmand's Blood Turnip variety were sown Apr. 24 in drill rows 18 inches distant. Later the seedlings were thinned until they were 5 inches apart.
Early Development.--The early root development of the beet is rather rapid. Under very favorable conditions for growth, laterals appear on the upper portion of the long taproot only 7 days after the seed is planted.
The first field examination was made June 4 when the plants were 6 weeks old. The tops were 5 inches tall and each plant had 6 to 8 half-grown leaves about 3 inches long and 2.5 inches wide. The total transpiring surface (two sides of the leaves) averaged 1 square foot.
The underground parts were characterized by strong taproots which reached depths of 2.5 feet. The upper portion of the root had already begun to thicken but below 4 inches it was only 1 to 2 millimeters in diameter (Fig. 19). Although slightly kinked and curved, the general course was vertically downward. Rapid growth was indicated by the long, unbranched root ends. Usually more than 100 branches arose in the surface foot of soil. They spread rather horizontally on all sides of the plant. The smaller ones were only 1 inch or less in length and unbranched. The longer ones extended away from the taproot for a distance of a foot or more and were well clothed with short, unbranched laterals. In the second foot the laterals were almost as abundant but only rarely over 0.3 inch in length.
Fig. 19.--A garden beet 6 weeks after the seed was planted.
Midsummer Growth.--A second examination, June 30, revealed marked development. The tops were nearly a foot in average height and each possessed about 16 large leaves. The area presented for photosynthesis and transpiration was very large since the leaf blades were approximately 8 inches long and 5 to 6 inches wide. It had increased to 4.8 square feet.
To supply water and soil nutrients for the rapidly growing tops, the plants had developed a remarkably extensive root system.
The fleshy taproots were now 1.7 inches in greatest diameter but tapered rapidly under the enlarged surface portion so that they were only 3 to 4 millimeters in diameter at a depth of 18 inches. Beyond this depth the taproots, now only 1 millimeter thick, continued their somewhat tortuous but usually vertical course, reaching depths of 60 to 65 inches in the compact subsoil. The taproot was profusely branched, except near the tip, throughout its entire course. The roots originated in two rows on opposite sides of the taproot which is also characteristic of sugar beets. 68 The vigorous growth of the plants was shown by the long, unbranched ends of the taproot and their larger branches. Often 8 to 11 inches of the root ends were entirely unbranched.
From the lower one-third to one-half of the "beet" many, fine, unbranched rootlets arose. These were only 1 to 2.5 inches in length. Within the first foot of soil the taproot gave rise to from 100 to 125 branches. Many of these (approximately one-third) were only 0.5 to 3 inches in length and entirely unbranched. They were very delicate and almost thread-like. The other branches were larger in diameter and varied in length from 4 inches to 3 feet. A few had a horizontal spread of 4.5 feet. Like the smaller laterals they nearly all took a horizontal or slightly downward course (Fig. 20). They were branched somewhat irregularly but often at the rate of two to eight laterals per inch. These small branches varied between 0.2 and 1.5 inches in length. Many were furnished with short sublaterals. Thus the surface foot of soil was already well ramified with the roots of this crop.
Fig. 20.--A beet about 10 weeks old.
In the second, third, and even in the fourth foot, branching was scarcely less pronounced. The fine laterals were shorter, however, and the longer ones had not had time to pursue their horizontal course for a distance greater than 2 feet from the taproot. Although the secondary branches were shorter, the tertiary ones were practically absent except in the second foot. The number of branches still ranged between two and eight per inch. In the upper portion of the third foot the soil structure was very compact. Owing perhaps to the hard soil, branching of the laterals was noticeably less than on the roots above or below this stratum. The tendency of the roots in the fourth foot to spread only a few inches horizontally and then turn downward was very characteristic. Like the taproots, the long unbranched root ends indicated rapid growth. On the younger, rapidly growing roots laterals were very short.
A somewhat cone-shaped volume of soil, with its apex at about the 5-foot level and its base extending 2 feet or more on all sides of the plant, was being drawn upon to furnish water and nutrients for each rapidly developing plant. This volume included about 21 cubic feet of soil and subsoil. The excavation, examination, and comparison of such an extensive root system were somewhat easier than usual because of the fact that all except the smallest roots were fairly tough. All but the youngest were characterized by the presence of anthocyanin in such abundance as to give them the characteristic dark-pink or reddish color of the "beet" proper.
Maturing Plants.--At the final examination, Aug. 12, 6 weeks later, the plants had an average height of 11 inches although some were 5 inches taller. Plants of average size possessed 24 large leaves, about one-third of which were dead and 4 to 6 of the younger ones were only partially developed. The 10 to 12 fully grown leaves had approximately 60 square inches each of photosynthetic area. The "beets" were now 3.5 to 4 inches in diameter.
The strong taproots had grown vertically downward, many to the 10-foot level; some reached a maximum depth of 11 feet. Large numbers of the formerly horizontal branches in the 2 feet of surface soil had extended laterally for distances of 2 to 4 feet, and then, turning rather abruptly downward, penetrated to depths of 4 to 6 feet (Fig. 21). Moreover, a remarkable development of the deeper portion of the root system had occurred.
Fig. 21.--Root system of the garden beet on Aug. 12, about 3.5 months after planting the seed. The taproot had elongated at an average rate of over 1 inch per day. Note the extensive absorbing area deep in the soil.
Here, the downward-growing tendency of the laterals, already shown late in June, was clearly evident. These vertical branches, paralleling the course of the taproot, thoroughly filled the deeper soil, some reaching depths nearly or quite as great as the taproot.
Approximately on the lower half of the "beet" short roots occurred in great profusion. Here, as in the sugar beet, they are confined to two broad rows on opposite sides of the root. As many as 150 roots were counted on a single individual. These roots seldom exceeded 8 inches in length and usually most of them were shorter. Some were unbranched but others were so profusely branched as to form a dense network of rootlets in the surface soil. The abundant branching of the taproots may be seen in Table 12 which illustrates a typical case.
TABLE 12.--NUMBER OF LATERALS ARISING FROM 1 INCH OF THE TAPROOT AT VARIOUS DEPTHS Number of Number of Number of Number of Depth, roots less roots greater Depth, roots less roots greater inches than 1 milli- than 1 milli- inches than 1 milli- than 1 milli- meter in meter in meter in meter in diameter diameter diameter diameter 5 29 4 13 17 2 6 26 5 14 20 1 7 14 4 15 to 2 10 to 15 2 8 12 1 20 to 25 6 to 10 0 9 20 2 25 to 30 6 to 8 1 10 19 3 30 to 35 2 to 6 1 11 25 2 35 to 40 2 to 7 3 12 16 1 40 to 45 3 to 8 3
Many of the smaller branches were hairlike, only 1 inch or less in length, and often free from branchlets. The larger laterals were frequently 1.5 to 2.5 millimeters thick throughout much of their course but all tapered to ½ millimeter or less in diameter several inches from their ends. The rate of branching was quite variable, ranging from 5 to 10 branches per inch. The branchlets were usually 0.1 to 4 inches in length and often quite well furnished with laterals. The course of the laterals may be best seen in the drawing. In the drier and more compact soil layer at a depth of 36 to 45 inches, branching was poorer and few of the roots were over 2 to 4 inches long. But at greater depths from 7 to 10 branches (maximum, 17) normally arose from each inch of the taproot. Some were of large size, ran obliquely, and then turned downward and penetrated deeply. They were clothed with sublaterals, 0.5 to 2 inches long, in numbers similar to that of the taproot. These were poorly rebranched. A working level of 7 feet was found. although numerous roots penetrated more deeply.
The entire root system had the characteristic red or pinkish color except the root ends which were bright and shiny white. Even these could be immediately identified by the taste as belonging to the beet. Earthworm burrows frequently occurred and seemed most abundant in the deeper soil. Upon entering them the roots branched much more profusely, the branches running parallel to the large laterals in the burrows. This resulted in dense masses of roots of rope-like structure. Some of these branches were also found running horizontally 10 to 12 inches at depths of 7 feet. Although some of the cobwebby mats of roots in the drier, upper soil layers had shriveled and died, examination of the bright, turgid, unbranched root ends clearly showed that the roots were still growing.
Root Development of Seed Beets.--Beets of the same variety were also grown in Oklahoma. They were left in the soil unprotected during the winter. Only about one-fourth of the plants survived so that they were spaced 1.5 to 2 feet apart in the rows which were 3.5 feet distant. The roots of these surviving plants were dead. Renewed growth of tops began about Mar. 1. Three weeks later 70 to 260 unbranched roots had developed from two rows on opposite sides of the fleshy, somewhat shriveled "beet." These were mostly horizontal or ran obliquely and only slightly downward. They were 0. 1 to 6 inches long.
By Apr. 18 the plant had a crown of leaves 6 to 9 inches high. Aside from a multitude of fine, hairlike rootlets, about 40 were 1 to 2 millimeters in diameter. These extended 6 to 18 inches on all sides of the plant (maximum spread 23 inches); some penetrated obliquely and reached a depth of 22 inches. Many ended in the 14- to 18-inch soil level. The older parts of the larger roots were furnished with laterals 3 to 4 inches long at the rate of four to six pet inch. Many of the smaller roots were also branched, so that quite a network of rootlets filled the soil. These new roots are necessary to supply the demands for water made by the new shoots. They also absorb food materials from the soil which supplement the supply accumulated the preceding year and which thus promote a good growth of tops and an abundant yield of seed.
The plants made a vigorous growth during May and by the end of the month were about 3 feet tall and had five to nine well-branched, leafy stems. In fact they had almost attained their maximum development. The flowering period was nearly passed and fruits had begun to mature.
The root system was very different from that of the first season. About 50 long roots, varying in diameter from 0. 5 to 2 millimeters, arose from the lower portion of the "beet" and from the 2 to 3 inches of the attenuated taproot which survived the winter. None of these roots had major branches but were cord-like in character, maintaining their original diameter almost throughout their course. Many of them grew rather parallel to the soil surface at depths of 3 to 12 inches, some reaching a distance of 37 feet from the base of the plant. Others penetrated outward and obliquely downward to distances of 12 to 24 inches or more and ended in the second foot of mellow, moist, sandy soil. Still others pursued a more vertically downward course. These extended deepest, the longest to the 35- to 41-inch soil level. The paths of some of the roots were quite tortuous. The root distribution and the degree of branching are shown in Fig. 22. The larger roots were rather poorly branched on their older portions near the plant (two to eight rootlets per inch). This part of the soil, however, was thoroughly ramified by finer, wellbranched rootlets. But throughout most of the course of the roots, except near their tips, branches, usually 1 to 4 inches long but mostly unbranched, occurred at the rate of 16 to 20 per inch.
Fig. 22.--A portion of the root system of a "seed beet" reset in the spring following the first season of growth. The old roots had died and all the firbous roots grew during the second season.
Thus the new root system was not only widely spreading but well furnished with efficient absorbing rootlets.
This root development is similar to that of "mother sugar beets " used for production of seed. In experiments with these it was found that the lower temperatures of early spring or late fall gave a more profuse and more extensive root development than when the beets were set out during warmer weather. This temperature relation was clearly marked.115
It is of interest to note that although the roots of the beets were entirely winterkilled, those of the carrot were only partially injured (see Chapter XXII), and the roots of the parsnip lived through the winter unharmed (see Chapter XXIV).
Summary.--The beet has a very pronounced tap root which grows at an average rate of over 1 inch per day during a period of 3.5 months. By the last of June it is 5 feet long and in August extends to the 10-foot level. Two types of branch roots occur in the first 2 feet of soil. The first is exceedingly numerous, short, and repeatedly rebranched. On mature plants they fill the soil in a cone-shaped volume about 16 inches wide near the surface. (where they grow out in rows on two sides of the "beet") to its apex at a depth of 2 feet. This portion of the root system develops rather late. Strong branches, intermingled with these shorter roots, also extend horizontally, or only slightly obliquely, some to a distance of 4 feet. Turning vertically downward they then 'reach depths of 3 to 6 feet. Below 2 feet branches from the taproot grow out more obliquely and turn downward in such a manner that the lateral spread scarcely exceeds 1 foot. They form, with the taproot, an efficient absorbing system in the deeper soil (2 to 8 feet). All of the main roots are profusely branched but with short laterals. Hence, although the root system is very extensive, the soil volume delimited by it is not fully occupied.
The root system of a "seed beet" consists of 40 to 60 fibrous or cord-like roots running horizontally, obliquely, or rather vertically downward. These are new roots which arise from the lower portion of the "beet" and the short remnant of the attenuated part of the original taproot. All are well clothed with unbranched laterals. They thoroughly ramify a hemispherical soil volume having a radius of about 3 feet.
Other Investigations on Beets.--It has been observed in Russia that during the first 3 weeks after planting the root development is weak. It later becomes accelerated to a point where the taproots grow 1.2 inches per day and the lateral branches elongate at one-half this rate. A root depth of nearly 5 feet and a horizontal spread of nearly 22 inches were attained. 123
An examination of the Extra Long Dark Blood beet at Geneva, N. Y., showed that the main root was smooth and symmetrical to a depth of 8 inches. Below this it divided into several branches, which were quite thick at first, but rapidly tapered to only a few millimeters in diameter and then to thread-like proportions.
One of the longer ones extended 2 feet downward, while horizontal branches, which were mostly shallow in the soil, extended a distance of 2.5 feet. The small fibrous roots seen on the surface of beet roots after they are pulled seem to have very little office, as they penetrate the soil scarcely ½ inch. The feeding roots chiefly proceed from the taproot, below the thickened portion. Fibrous roots from the branches often extend upward apparently to the surface of the ground. The root system of the Eclipse beet, which is a turnip-rooted variety, growing largely above ground, is precisely similar in kind but slightly less extensive. We traced the roots downward about 22 inches, and horizontally a distance of 2 feet. 43
There has been observed at this station an early variety of beet and also of radish which appeared to root shallower than later ones, although no such differences were found in lettuce and pea. 44
The rooting habits of Crosby Egyptian beet, an early variety, was also studied at Ithaca, N. Y. They were grown in a fertile gravelly sandy loam soil underlain at a depth of 8 to 12 inches with gravelly sandy loam which became sandier at increasing depths. On plants 12 inches tall and with the fleshy taproot 0.5 to 1 inch in diameter, very few roots had penetrated to a greater depth than 6 inches, although the taproot reached a depth of 15 inches. The space between the 18-inch rows was fairly well filled with roots to the depth of 4 inches. When the plants were nearly fully grown and the beets 2.5 to 3.5 inches in diameter the taproot extended to a depth of 2 feet, and some branches from this to 30 inches. Small branch roots developed from the taproot throughout its length, some of which were 18 inches long. Near the surface a large number of roots ran almost horizontally and extended from one row to another, there being nearly as many in the centers as near the rows. The lateral roots were small and of nearly the same size throughout their length and had many small branch roots. The greatest development of roots was found in the surface 3 or 4 inches of soil where they extended from one row to another, there. being nearly as many in the centers as near the rows, and many were so near the surface that any kind of cultivation would result in some destruction. 159a
Root Habit Compared with the Sugar Beet.--The sugar beet is one of the forms of the complex species, Beta vulgaris, quite similar to the garden beet in root habit. Like the garden beet it develops a strong, deep taproot, a surface root system of profuse, much-branched, widely spreading laterals, and a more vertically penetrating but extensive system of branches which ramify the deeper soil. Extensive experiments in fine sandy loam soil at Greeley, Colo., have shown that the root system is very susceptible to modifications brought about in the soil environment by variations in the water content, fertility, etc. 68 It seems prob able that the garden beet would respond in a similar manner. For example, the Kleinwanzelebener variety of sugar beet in dry soil had a smaller taproot which pursued a more tortuous course, did not penetrate so deeply, and was branched more nearly to the tip than similar plants in moist soil. The larger, deeper-seated branches turned downward rather abruptly, reaching depths of 3 to 4 feet. Branching was more profuse throughout. Development of the surface absorbing system may be greatly delayed, although it branches more profusely and may extend even more widely when the soil becomes moist. The root systems of mature plants grown under irrigation and other very favorable conditions were less extensive than that of the garden beet. Depths of 5 to 6 feet were attained and the lateral spread seldom exceeded 18 inches.
Studies in Germany show that not only the sugar beet but also mangels and certain other closely related, fleshy rooted forms are very similar in habit to the garden beet just described. 83
Root Habits in Relation to Cultural Practice.--The very deeply penetrating root system of the beet explains why, like other root crops, it thrives best in a deep, friable, well-drained, but moist soil. A consideration of the very fleshy portion of the taproot makes clear why a deep, mellow, easily moved soil is essential for a proper development of the beet. In heavy soil the beets are likely to be unsymmetrical in form. Hence, in preparing the seed bed the soil should be well pulverized, loose, and smooth, but not so loose that it quickly dries. A heavy soil is less satisfactory. It becomes hard and cracks or if kept wet it puddles, conditions very unfavorable for the germination of seed. The actual depth of cultivation varies, of course, with the nature of the soil and the previous depth of cultivation. Poor soil preparation is likely to result in an inferior stand of plants, regardless of the high quality of the seed sown. No amount of later cultivation will compensate for carelessness in the preparation of a seed bed. Early and frequent tillage not only keeps down weeds but also prevents the formation of a soil crust and the subsequent difficulty in the emergence of the shoot. It promotes good aeration.
Since each fruit of the beet contains more than one seed, the plants come up in clumps and must be thinned. The time and manner of thinning is closely related to root injury. Late thinning greatly disturbs the roots of even the more vigorous plants left to mature. The widely spreading and deeply penetrating root systems are undoubtedly an important factor in competition and the resultant reduction of yield where the crop is too thickly grown.
A study of the root system shows that the beet used in this investigation did not depend largely on the surface 4 to 6 inches of the soil for its water and nutrient supplies. A comparison of the soil-moisture data in Table 2 shows that cabbage (as is indicated by its more superficial root system, Fig. 29) reduced the water content in the surface foot of the soil to a much greater degree than did the beet. At greater depths, however, the soil in the beet plats was usually drier. It would seem that cultivation of the soil for the purpose of retaining moisture should have some advantage over removing the weeds by scraping. 152,158 At Ithaca, N. Y., an average gain in yield of 4.25 per cent as a result of a soil mulch has been reported for an early beet which rooted extensively in the surface soil. 159a The large tops, of course, would more or less thoroughly shade the soil and thus retard surface evaporation. Only a few inches of surface soil, except that close to the plant, were, under the conditions of growth described, unoccupied by roots. The lack of superficial roots, except those very close to the plant, permits of deeper cultivation without root injury than is possible in the case of many garden crops. Some varieties, however, and perhaps all varieties under certain conditions, fill the surface soil also with a network of roots. Likewise, a practice of getting manure and other fertilizer worked well into the deeper soil would seem justifiable. This would not only place the manure more easily within the reach of the roots but also at the same time improve the physical condition of the soil.
The close spacing of beets, usually 4 to 8 inches apart in drills or rows 1 to 2.5 feet distant, results in much overlapping of absorbing territory and a thorough occupancy of every cubic inch of soil. It is not surprising that garden soils must be kept very rich where, as is often the case, beets are grown as companion or succession crops.