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   Rye (Secale cereale) is an annual and, like winter wheat, makes a good growth when planted in the autumn. Only rarely is it sowed in the spring. Upon germination, it rather regularly produces a whorl of four roots which constitutes the primary root system, thus differing from the other cereals which usually have only three. The mature root system is very similar to that of oats and spring wheat.

   Mature Root System.--Plants were grown near Lincoln on rich silt loam soil underlaid with a moist but hard clayey subsoil. The tops at harvest time were 5.5 feet tall and the maximum root penetration was 5 feet. Relatively few roots extended so deeply and the working depth was about 4 feet. Similar depths of penetration were found for Rosen rye growing in an adjacent field, although the tops were 6.5 feet tall. In both cases, the roots were exceedingly well branched to the working depth. In fact, branching is usually better developed in rye than in wheat or oats when growing in the same kind of soil and under the same conditions of moisture. This is one reason why rye is adapted to drier climates than wheat and will thrive on poorer and sandier soils than any of the other cereals. It sometimes produces a fair crop under adverse conditions where other small grains would fail completely. In this connection, the work of Nobbe (1869) is interesting. 147 He compared, measured, and counted the roots of winter wheat and rye plants grown in soil when 55 days old. He found that the roots of the first to the fourth order numbered 16,000 in rye and 10,700 in wheat. The combined lengths of these roots measured 118 and 82 meters, respectively.

   Root Variations under Different Soils and Climates.--The development of both shoots and roots of rye is greatly affected by differences in soil. Near Fairbury, in eastern Nebraska, plants in silty clay loam upland soil had a height growth of 4.5 feet, a working depth of 4.7 feet, and a maximum penetration of 5.2 feet. But a crop from the same lot of seed planted at the same time (Sept. 4) on alluvial soil of mellow silt loam was very different. The height of tops was 3.8 feet, which was also the working depth of the roots. Practically all of the roots ended abruptly at this level below which there occurred nearly pure sand. A similar rooting habit has been found for winter rye at Fargo, N. D. 186

   Fig. 75.--Root system of rye grown in rather dry sandy soil in eastern Colorado.

   The extensive growth made by the roots of rye in sandy soil, even under a meager precipitation, is shown in Fig. 75. The wide lateral spread is very characteristic of cereals grown in sand, a habit not unlike that of the native grasses. The first 4 to 6 inches of roots at the bases of the plants were almost woolly with dense masses of root hairs to which the sand clung tenaciously. The roots soon began to branch with delicate, hair-like branches ½ inch to 3 or 4 inches in length, some being even longer. They ran in all directions, even obliquely upward, and were fairly well rebranched to the second order. The most profuse branching was in the deeper soil where, in places, as many as 10 to 30 laterals were found on a single inch of root.

   Rye grown in sandy soil under a greater precipitation penetrated, even deeper (Fig. 76). The crop had been drilled in this field, near Central City in eastern Nebraska, early in September. It was grown to retard the. blowing of the sand (Fig. 27), since it is better adapted to sandy soil than, any of the other grain crops. The prevalence of wind action was clearly illustrated by the stratified soil. The surface 1.3 feet of nearly pure sand was underlaid by 1.3 feet of dark- colored sandy loam. Below this, pure sand occurred to the water level at 7.5 feet. The number of main roots varied, according to the amount of tillering, from 15 to 40. The lateral spread seldom exceeded 14 inches, but roots were fairly abundant to 6 feet. Few differences were noted in the degree of branching, etc., in passing from one soil layer to another. Plants grown in pure sand, because of the low fertil ity, had both root and shoo t development greatly abbreviated.

   Fig. 76.--Deeply penetrating roots of rye grown in moist sandy soil in eastern Nebraska. Scale in feet.

   On the "hard lands" of the short-grass plains, the root extent of rye, like that of the other cereals, is limited by the depth of moist soil. A carbonate layer occurs usually at 1.5 to 2.5 feet in depth, and the root system is frequently entirely confined to the soil above this layer. Under these conditions, lateral spread and degree of branching are exceptionally pronounced. An unusual amount of rainfall or irrigation, if sufficient to moisten the hardpan and deeper subsoil, produces a more normal development of roots and a correspondingly better growth of tops. Variations in growth under different types of climate and soils are summarized in Table 9.

TABLE 9.--VARIATIONS IN GROWTH OF RYE UNDER DIFFERENT TYPES OF
          CLIMATE AND SOIL

                                             Height  Work-  Maxi
                  Variety                      of     ing    mum
Station           of crop   Soil              tops,  depth, depth,
                                              feet    feet   feet

Short-grass plains:
Yuma, Colo        Winter    Very fine sandy
                              loam             2.3     2.2    2.8
Flagler, Colo     Winter    Very fine sandy
                              loam             2.1     2.3    2.8
Burlington, Colo  Winter    Very fine sandy
                              loam             3.5     4.3    6.0
Limon, Colo       Winter    Very fine sandy 
                              loam             2.3     2.0    2.0
Colby, Kan        Winter    Very fine sandy
                              loam             3.5     3.0    3.6

            Averages ......................... 2.7     2.8    3.4

Mixed prairie:
Yuma, Colo        Winter    Very sandy loam    2.7     4.2    5.0
Colorado Springs,
  Colo            Winter    Sandy loam         3.0     3.0    4.7
Mankato, Kan      Winter    Very fine sandy
                              loam             4.2     3.8    4.7

            Averages ......................... 3.3     3.7    4.8

Tall-grass prairie:
Central City,
  Nebr            Winter     Very sandy loam   6.0     5.0    7.7
Central City,
  Nebr            Winter     Pure sand         3.3     2.8    4.6
Lincoln, Nebr     Winter     Silt loam         5.5     3.9    5.0
Lincoln, Nebr     Winter
                    Rosen    Silt loam         6.5     3.7    5.0
Fairbury, Nebr    Winter     Clay loam         4.5     4.7    5.2
Fairbury, Nebr    Winter     Alluvial          3.8     3.9    4.2

            Averages ......................... 4.9     4.0    5.3

   Rye is a winter annual. Upon germination, a primary root system of four roots is produced. Later, numerous fibrous roots of the secondary system appear, the total number varying with the degree of tillering. In moist silt loam, the roots usually have a lateral spread of 6 to 10 inches, a working depth of about 4 feet, and a maximum penetration of 5 feet. Branching is usually better developed than in either wheat or oats when grown in the same kind of soil. Root habit varies greatly with environment. In sandy soil, the roots spread 12 to 14 inches near the surface and frequently penetrate to depths of 5 to 7.5 feet. Profuse branching may occur to the root ends. In soils of low water con tent underlaid with dry subsoil, the whole root system is frequently confined to the surface 2 to 2.5 feet. Under these conditions, widely spreading surface laterals and profuse branch ing throughout are especially characteristic. Growth in height varies somewhat directly with depth of root penetration.