Rye may serve as grain, hay, pasture, cover crop, green fodder and green manure. Depending on the utilization several traits have to be considered not only in breeding but also for the technology (Tab. 8.1).
Rye is a good pioneer crop for sterile soils. When used as a cover crop, it is grown for erosion control, to add organic matter, to enhance soil life, and for weed suppression. It may also stabilize and prevent leaching of excess soil or manure nitrogen. It has been used to protect soil from wind erosion in exposed areas and, with its tall stature, may be of some value in providing windbreaks. It is a good green manure because it produces large quantities of organic matter but should be used only in rotation with row crops because other grain crops are graded down in the market if they contain rye seed.
Recommended seeding depths include 2.5 to 5.0 cm. The suggested seeding rates are 90-112 kg/ha. Optimal seed rate for hybrid material is about 150 seeds/m². When rye is seeded late the rate should be increased up to 336 kg/ha to achieve rapid and complete vegetational cover and reduce erosion. To minimize erosion, a leaf area index of 1.0, i.e. complete cover, may be necessary.
Rye grows best on well-drained loam or clay loam soils, but even heavy clays, light sands, and infertile or poorly drained soils are feasible. It will grow on soils too poor to produce other grains or clover. On light sandy soils rye can produce more than 7 t/ha in several years when hybrid varieties are grown. In general, it is tolerant of different soil types. Rye is well known to tolerate acid soil. The range of best suitability is pH 5.0-7.0, but tolerance is between 4.5 and 8.0. Therefore, rye also shows high aluminum tolerance (Gallego and Benito, 1997). It even gives good yields on poor, sandy soils and does better than oat on sandy soil.
Rye grows best with ample moisture, but in general it does better in low rainfall regions than do legumes and it can outyield other cereals on droughty, sandy, infertile soils. Its extensive root system enables it to be the most drought-tolerant cereal crop, and its maturation date can alter based on moisture availability. The structure of the rye plant enables it to capture and hold protective snow cover, which enhances winter-hardiness. This snow retention might also be expected to enhance water availability. However, under intensive condition of rye production a dense stand of plants in autumn can promote the growth of snow mold. Diploid varieties are more drought tolerant than are those that are tetraploid. Rye requires about 20-30 % less water than wheat per unit of dry matter formation.
In plant physiology rye is recognized among cereals as genotype showing high ability for uptake of micronutrients, e.g. under iron, copper, manganese and zinc deficiency (Erenoglu et al., 1999). When grown in zinc-deficient calcareous soil in the field, the rye cultivars had the highest, and the durum wheat the lowest zinc efficiency. Under zinc deficiency, rye had the highest rate of root-to-shoot translocation of zinc. The results indicated that high zinc efficiency of rye could be attributed to its greater zinc uptake capacity from soils. By utilization of wheat-rye addition lines it was demonstrated that genes on chromosome arms 1RS and 7RS are associated with high zinc efficiency (Schlegel et al., 1999).
Already earlier, it was found that rye shows the ability to take up iron and copper under deficient conditions (Podlesak et al., 1990). As shown by Marschner et al. (1989) and Treeby et al. (1989) the release of phytosiderophores is the main mechanism of grasses to acquire iron and copper in the rhizosphere. An initial study demonstrated that rye secretes mainly 3-hydroxymugineic acid under iron-deficiency conditions, but also mugineic acid and 2’-deoxymugineic acid (Mori et al., 1990). The latter authors found a clear correlation between high amounts of those chelators and the presence of chromosome 5R in wheat rye addition lines. Later the genes for high copper and iron efficiency were physically mapped on the distal region of chromosome arm 5RL by using a specific wheat-rye translocation lines (Schlegel et al., 1993).
The different behavior of root uptake is not necessarily correlated with the concentration of micronutrients in the shoot (Schlegel et al., 1997). Nevertheless, the chromosomes 2R and 7R were associated with improved manganese and iron concentrations in the shoots, chromosome 1R with zinc and 5R with copper concentration, respectively.
Rye even produces high yield under poor soil conditions and without or limited extra dressing. Intensive systems of rye production require additional nitrogen during the starting phase of vegetation. It promotes tillering and spikelet fertility. Depending on the soil and the variety up to 30-50 kg/ha N can be recommended. Application of nitrogen during the period of shoot emerging and two-node-stage influences the stand density. However, to dense stands are susceptible to lodging. In order to utilize the yield potential, a third portion of nitrogen can be applied during the stage of spike emerging, however, when sufficient water resources are available.
The application of sludge is possible, however in limited amounts. Precise calculations of mineral fertilizers have to be considered.
Rye is grown in the cool temperate zones or at high altitudes. It is the most winter hardy of all small cereal grains. Its cold tolerance exceeds that of wheat, including the most hardy winter wheat varieties, and it is seldom injured by cold weather. Alien cytoplasms may even increase cold tolerance (Limin and Fowler, 1984). It can be established when seeded as late as October 1. Minimal temperatures for germinating rye seed have been variously given as 1 to 5 °C. It grows better in cooler weather. Vegetative growth for rye requires a temperature of at least 4 °C. It also can be incorporated earlier in the spring as compared to other cereals. It is one of the best crops where fertility is low and winter temperatures are extreme.
SUSCEPTIBILITY AND RESISTANCE
Rye is afflicted by the following fungi: powdery mildew (Erysiphe graminis), ergot of rye (Claviceps purpurea), take-all of wheat (Gaeumannomyces graminis, Ophiobolus graminis), stalk smut (Urocystis occulta), stem rust (Puccinia graminis f. secalis), brown leaf rust (Puccinia dispersa) yellow rust (Puccinia striiformis, Puccinia glumarum), eyespot (Cercosporella herpotrichoides), snow mold (Fusarium nivale), fusariosis of rye spikes (Fusarium spp.), spot blotch (Helminthosporium sativum, Bipolaris sorokiniana), black mold (Cladosporium herbarium), anthracnose (Colletotrichum graminicola), septoria leaf blotch (Septoria secalis), and leaf blotch of rye (Rhynchosporium secalis). Viral diseases include barley yellow dwarf, wheat dwarf, soil-borne mosaic, and oat blue dwarf. Rye is susceptible to glyphosate and to paraquat.
It may be also attacked by nematodes, such as Ditylenchus dipsaci, Anguina tritici and Heterodera avenae. Wheat, potato, turnip, lupin, alfalfa, and white mustard can be grown preceding rye to reduce D. dipsaci. Clean seed and crop rotation reduces A. tritici. The use of leguminous and root crops in rotation reduces H. avenae. Rye harbors particularly low densities of root lesion nematode (Pratylynchus penetrans).
Because of plant height of common rye varieties the lodging resistance is reduced. Lodging significantly decreases grain yield and quality, despite more costly harvest. Even when seeding rate is and nitrogen dressing is optimal, twice growth regulators can be applied for stem reduction, considering the specific characteristics of the variety, local and climatic conditions. Before and after application of growth regulators there should be sufficient soil moisture!
INCORPORATION IN CROP ROTATION
Rye is very suitable for several crop rotations showing high adaptability. The new hybrid varieties show high yield potential and, if an optimal cropping technique is used, outyield other cereals under comparable agronomic conditions. However, wheat is usually grown on the better soils and it receives more attention within the crop rotation. Often the production is suboptimal so that the yield potential of rye is made use in lower measure. Trials where rye is grown in monoculture or in rotation with winter wheat and winter barley showed the better yield performance of rye. Rye has been shown to be allelopathic towards other plants, but some of the suppressive effects may relate to tie-up of soil nitrogen by decomposing rye residues. It also can inhibit germination or growth of vegetable crops sown after rye is incorporated. In some countries, it is sown with legumes or other grasses.
Rye produces several compounds that inhibit crops and weeds. Rye provides excellent weed suppression through both allelopathic and competitive mechanisms. Rye residues maintained on the soil surface release 2,4-dihydroxy-1,4(2H)-benzoxazin-3-one (DIBOA) and a breakdown product 2(3H)-benzoxazalinone (BOA) both of which are strongly inhibitory to germination and seedling growth of several dicot- and monocotyledonous plant species (Chase et al., 1991a, b). Further, microbially produced transformation products of BOA demonstrate several fold increases in phytotoxic levels. Hence, a variety of natural products contribute to the herbicidal activity of rye residues. Several studies have demonstrated the allelopathic characteristics of rye residues and root exudates containing DIBOA and BOA. Experiments have shown marked reductions in germination and growth of several problem agronomic weeds including barnyardgrass (Echinochloa crusgalli), common lambsquarters (Chenopodium album), common ragweed (Ambrosia artemisiifolia), green foxtail (Setaria viridis) and redroot pigweed (Amaranthus retroflexus).
Rye can become a weed through volunteering and sometimes escapes in waste places and fields, e.g., it is a common weed. In some areas, it grows even with only 15-20 l/m² of precipitation.