Kans. State Agric. College Bul. 127: 201-207 (June 1904)
The Roots of Plants
A. M. Ten Eyck

CORN ROOTS
(Lister versus level planting)

Planting with a lister.

In the study of corn roots, the purpose was not only to exhibit the root development of the plant, but to compare the root systems produced by the level and lister methods of planting. The corn was planted May 19, on new spring plowing. Part of the ground was listed in furrows about six inches deep, and all of the corn was planted with a check-row planter, in hills three and one-half feet apart each way. The variety of corn used was the Kansas Sunflower, a rather late maturing sort and a medium grower. The first set of samples were taken July 18-23, sixty days after planting. The corn stood about five feet high at that date, and had been cultivated for the last time ten days previous to taking the samples. It was the plan to cultivate shallow, in order not to injure the roots of the corn, but through an error, at the third cultivation, June 30, a six-shovel cultivator was used, and it is possible that the cultivation was sufficiently deep to destroy some roots.

Plate 1 is an illustration of the sample of the level-planted corn taken sixty days after planting. It shows the development and distribution of the roots between the hills of corn in adjacent rows. At the first observation, one is surprised at the large number of roots and their extensive growth. At this stage the corn has filled the soil with its roots, not only beneath the hills but between them, until the entire space was fully occupied to the depth of two and one-half feet, and some roots reached a depth of more than three feet. The roots are thrown off from the base of the stalks in quite uniform whorls, arranged one above the other, the whole forming a root-crown which in this sample measured ten to twelve inches in diameter near the surface of the ground.

From the illustration two classes of roots are easily distinguished: Those that curve out from the crown and strike more or less directly downward into the soil, i. e., the main vertical roots, and those that spread out from the root-stem in a horizontal plane, near the surface of the ground, the main lateral roots. In this sample the lateral roots curve downward as they leave the crown, and then extend out in an almost horizontal plane, the roots from opposite hills meeting and interlacing, when they curve more or less abruptly downward, often ending two or three feet beneath the opposite hill. In their horizontal course these roots have given off many vertical branches, which have penetrated the subsoil and reached a depth almost equal to that of the primary vertical roots directly beneath the hill.

In this sample the main roots were about four inches from the surface of the ground midway between the hills, are eight or ten inches from the hill they were three inches beneath the surface, and at four or five inches from the hill the outer roots of the root-crown reached the surface, and many large brace roots extended two or three inches above the ground. The bulk of the lateral roots lie between three inches and twelve inches from the surface. Some small fibrous roots were observed above the main lateral growth, showing that the small feeding roots grow upward as well as downward and to the sides. This upward growth was more noticeable in the samples taken at maturity. Some of the main roots strike out at an angle, gradually curving downward with the branches from the horizontal roots. The vertical as well as the horizontal roots give off numerous branches, the branches in turn give off other branches, and these produce smaller fibers and root-hairs, so that the whole soil at this stage of growth, to the depth of two and one-half feet, served as a feeding-ground for the crop.

Plate 2 shows the root system of the corn which was planted in lister furrows. The sample was taken sixty-five days after planting. The early part of the season was very wet and rather unfavorable to the growth of listed corn, and the stalks of corn in these two hills were not quite so large as those in the hills of the level-planted corn; also, the roots of the listed corn appear to be less numerous and have made somewhat less growth than the others, although having much the same general arrangement and distribution in the soil. The main difference in the two root systems appears in the difference in the location and form of the root-crowns. While the root-crown of the level-planted corn rises to the surface of the ground in a compact, fibrous mass, from which the roots curve downward and outward into the soil, the root-crown of the listed sample is located fully three inches deeper in the ground and is less compact and fibrous, and the lateral roots extend directly from the root-stem in an almost horizontal direction, the depth at the hill being practically the same as the depth midway between the hills. Thus, although the lateral roots of the listed corn were found within four inches of the surface, midway between the hills, yet the average depth of the roots was greater than in the level-planted corn, in which the lateral roots rise nearer the surface at the root-crown.

*Later study in the spring of 1904, after this bulletin was prepared for publication, indicates that, when the middles between the listed rows are unplowed and hard, the lateral roots actually rise nearer the surface as they extend outward from the root-crown. Thus the depth of the lateral roots midway between the rows may be less with the listed corn than with the level-planted corn, when the latter is planted in a deep, mellow seed-bed.

It is the general experience of farmers who practice the lister method of planting that listed corn stands drought better than level-planted corn. This study of the root systems offers a suggestion as to the reason why: It is evident that the listed corn could have been cultivated deeper and closer to the hill at the last cultivation, without injuring the roots, than the level-planted corn. The root-crown forms deeper in the soil and, as cultivation progresses, the furrow is gradually filled until, at the last cultivation, the ground is left practically level, with three or four inches of mellow soil over the roots close up to the hill. The root-crown and the main roots of the corn are well covered and the whole soil is completely protected by a deep soil mulch, which conserves the soil moisture and protects the corn roots from the extreme heat of the summer sun much more than could be the case if the root-crown rose to the surface as it does in the level-planted corn. Although the root-crown and the main lateral root system of the listed corn lie deeper in the soil than in the level-planted corn, yet there was apparently no loss of feeding-ground for the roots, since it was observed in washing out the sample that the soil above the main roots was filled with numerous slender, hair-like roots, branches from the main roots, which seemed to feed almost to the surface of the soil. These small roots were either broken off in washing, or, having no support, sank down upon the main lateral roots when the earth was removed. *

Plate 3 is an illustration of the sample of listed corn showing the root development at maturity, 125 days after planting. The stalks averaged about eight feet in height. The ears were nearly ripe, but the stalks and leaves were green and the roots were still alive and apparently growing when the sample was taken. At maturity the roots had reached a depth of fully four feet, and some were traced to the depth of five feet, but it was very difficult to wash them out to that depth because of the tenacious, clayey character of the deeper subsoil. Comparing this sample with those taken earlier in the season, it will be observed that the amount of root growth has greatly increased. The arrangement of the root system is much the same as that of the earlier sample of listed corn already described, but the root-crown has greatly increased in size and density and appears a little nearer to the surface, although midway between the rows the roots are slightly deeper than was observed in the first sample taken.

Plate 4 shows the root system of the level-planted corn at maturity. This sample was taken a few days later than the listed-corn sample just described. It should, however, have been taken before the other, because it was the riper corn. The ears were fully rip'e and the leaves and stalks were beginning to turn brown when the sample was taken. In this sample the roots reached fully as deep into the ground, but the number of roots and the fibrous growth was less than in the sample of listed corn. The root-crowns lie near the surface but midway between the rows; the lateral roots are deeper than in the sample taken earlier, those from the hill on the right being nearly six inches beneath the surface. Compared with the sample taken earlier in the season, this seems to be an irregularity in growth, or it may be that the roots of this hill received some injury from the cultivator. The apparently thinner and less fibrous growth of the roots in this sample may also be due partly to the fact that the corn was overripe and the roots broke and washed away more easily than did the roots of the listed corn.

In taking the sample at maturity, it was observed, both in the listed and level-planted corn, that the soil above the main roots was filled with a fine fibrous growth of roots to within one-half inch of the surface. Thus the fact that the main roots lie several inches from the surface does not prevent the crop from feeding in the more fertile surface soil. That the roots of plants may readily grow upward in the soil is evidenced by examining celery after it has been banked for several weeks. When digging celery last fall, the writer found the soil full of the slender, white roots of the plants twelve inches above the root-crowns.

SOIL MOISTURE CONSERVED BY LISTING CORN

A comparison of the soil moisture found in adjacent plots of listed and level-planted corn last season showed little difference in the amount of moisture in the soil of the two plots during the first part of the season. The level-planted corn was laid by July 2, part of it receiving shallow cultivation and part being cultivated deep. The listed corn was cultivated for the last time July 6, with a six-shovel cultivator, which left the surface fine and mellow to the depth of three or four inches. Soil samples, taken July 29 gave the following results:

Moisture in soil. Samples taken July 29, 1904.
  First
foot
Second
foot
Third
foot
Fourth
foot
Fifth
foot
Sixth
foot
Listed corn
Level-planted corn
14.71% 
12.63   
22.31%
20.10   
23.11%
20.81   
21.28%
18.35   
20.80%
18.84   
20.34%
19.07   
Differences 2.08 2.21 2.30 2.93 1.96 1.27
Average difference 2.12 per cent., in favor of the listed-corn plot.

It appears from the results given above, that more moisture was conserved in the listed plot than in the level-planted plot, after the corn was laid by. The early part of the season of 1903 was too wet and cold for listed corn; hence the level-planted corn thrived best, and produced the larger crop by about eight bushels per acre, the comparative yields being 52.3 and 44.4 bushels per acre, respectively. The larger crop would require more soil moisture, which may account partly for the lower per cent. in the level-planted plot. No moisture determinations were made at the close of the season.

DEEP OR SHALLOW CULTIVATION

Since the roots of corn spread out near the surface of the ground, it is evident that too deep cultivation (or too close cultivation of level-planted corn) will cut the roots and is apt to injure the corn. In many experiments reported from other states, the results have often favored shallow cultivation of corn as opposed to deep cultivation. As a rule, however, the deep cultivation in such experiments was extremely deep, usually five to six inches. Medium deep cultivation, three or four inches, and not too close to the corn, should not injure the roots, and in some soils and climates the deeper cultivation may often give better results than shallow cultivation. In 1893-'97 a series of experiments in corn cultivation were carried on at this Station. In summing up the results of these experiments, in Bulletin No. 64 of this Station, Professor Georgeson says: "Our experience also seems to indicate that it is not best to pin one's faith strictly to the shallow culture. . . . A judicious mixture of shallow and deep cultivation gives better results than to continue either one through the entire season."

*King's Agricultural Physics, page 186.

Too deep cultivation not only injures the corn by destroying the roots, but, during the period of cultivation, it prevents the roots from feeding in the most fertile part of the soil. On the other hand, the practice of shallow cultivation may be carried too far. A relatively thick mulch of mellow soil will conserve more moisture than a thin mulch, as shown by King in his experiments in Wisconsin.* As regards the conservation of soil moisture, the early cultivation of corn may be shallow. A deep soil mulch is not required at this season of the year, since the weather is moist and cool and evaporation is not great. But later in the season, when the hot, dry days of July and August come, a deeper mulch is necessary in order to keep the soil from dying out. Shallow cultivation early in the season also clears the ground of weeds better than deep cultivation, and a thin mulch may favor the quicker warming of the soil in spring. Loose soil is not so good a heat conductor as firm soil, and more heat can reach the firm soil through a thin mulch than through a thick mulch. On the other hand, in the hot part of the season the thick mulch may act as a regulator of the soil temperature and prevent the soil from becoming too hot as well as too dry.

North Dakota Bulletin No. 51, and 13th Biennial Report
Kansas State Board of Agriculture, page 798.

Cultivation experiments with corn at the North Dakota Experiment Station, and also at the Illinois station, gave yields favoring the shallow cultivation early, followed by deep cultivation, as opposed to deep cultivation early, followed by shallow cultivation.†

In the cultivation experiments made with corn at this Station last season, the yields did not vary sufficiently to be worthy of note. Samples of soil were taken from the several plots early in the season before cultivation was begun, and again at the close of cultivation. At the early date the moisture was found to be about the same in all plots. In the following tables the moisture content of the several plots, about two weeks after the corn was laid by, is compared.

The deeper cultivation as the corn was laid by seems to have conserved more moisture than the shallow cultivation. No moisture determinations were made at the close of the season.

Moisture in the soil. Samples taken July 16, 1903.
Kind of cultivation First
foot
Second
foot
Third
foot
Fourth
foot
Fifth
foot
Sixth
foot
Shallow
Deep
22.15%
21.52   
26.55%
25.21   
25.05%
27.59   
22.99%
23.99   
22.54%
22.41   
22.63%
22.08   
Differences  0.63% 1.34 2.54 1.00 .13 .55
Average difference 0.13 per cent., in favor of deep cultivation.

 

Moisture in the soil. Samples taken July 16, 1903.
Kind of cultivation First
foot
Second
foot
Third
foot
Fourth
foot
Fifth
foot
Sixth
foot
Deep early, shallow late
Shallow early, deep late
21.12%
22.03   
20.38%
28.72   
23.02%
26.17   
21.24%
21.44   
21.05%
21.28   
21.64%
20.77   
Differences -0.91 -8.34 -3.15 -0.20 -0.23 0.87
Average difference of 1.99 per cent., in favor of shallow early and deep late cultivation.

 

Plate 1   Plate 2
 
Showing distribution of roots between two hills of level-planted corn, sixty days after planting.   Showing distribution of roots between two hills of corn planted in lister furrows, sixty-five days after planting.
Plate 3   Plate 4
 
Roots of corn at maturity, planted in lister furrows.   Roots of corn at maturity, planted with check-row, level planter.