Description
Crop species:
1. Common alfalfa (Medicago sativa):
With purple, violet, and blue flowers, it is the most important crop in the world and this species constitutes over 90% of alfalfa grown in Iran. The plant height in this species varies from 60 cm to 100 cm and is well resistant to hot and cold weather.
2. Sickle hay or yellow flower (Medicago falcate):
With yellow flowers and sickle-shaped fruit, it has played an important role in the evolution of common alfalfa. It is highly resistant to cold weather and tolerates 60 Celsius degrees of temperature well under some conditions.
3- Medicago Media Alfalfa:
This group of alfalfa is a hybrid of first and second groups of alfalfa mentioned above and is suitable for temperate regions. The flowers of this species can be seen in pink, white and yellow colors. The height of this alfalfa varies from 80-50 cm.
Botanical characteristics:
A. Root:
Alfalfa has 2 types of roots:
1 – Main root: straight – deep – thick that in suitable soil texture can penetrate to a depth of 7 meters in the soil.
2 – Lateral roots: Shot out from the main root, lateral roots are responsible for plant strength in the soil and absorption of water and salts. Fixing Nitrogen nodes comprising Rhizobium meliloti bacteria group from symbiotic bacteria (Rhizobium) genus are formed on these roots.
B. Stem:
The main stem of alfalfa becomes thick and woody near the ground surface over time and turns into a crown. At the crown site there are buds that later turn into alfalfa stems. Depending on the genotype, the number of stems that shoot out of the crown vary between 5 to 40. The stems grow in height from 40 to 80 cm and sometimes reach up to 1 meter. Green stems have a large kernel and are of significant value. The percentage of protein also varies in different organs of alfalfa, so that in main stems it is 10 to 11 percent, in branches, 13 to 16 percent, in leaves 21 to 23 percent, and in flowers 31 to 34 percent.
C. Leaves:
After germination, alfalfa forms a pair of leaves called cotyledon from the center of which the first simple heart-shaped leaf appears with a long leaf tail. The main leaves are 3-leaflet leaves. The leaflets are elliptical with jagged hairy margins so that the middle leaflet is connected to the main petiole by a short leaflet tail but the two side leaflets are connected without any leaflet tails.
D. Flower
Flower arrangement in an array of a composite cluster with a very long flower tail on which may exist 5 to 50 flowers. The flower bowl is made of 5 connected sepals and the flower cup consists of five petals as follows. The largest petal is called standard petal. The two small petals are called wing petals. The smallest two are called keel petals. The number of flags is 10, of which nine are interconnected and one is free. This (9 + 1) arrangement is called Diadelph. If the flags are together, it is called Monodelf. Alfalfa is an allogamous plant, but it also is about 10% autogamous.
Inoculation is done by insects, especially honeybees. When bees sit on flowers to suck nectar, as soon as their bodies come in contact with keel petals, they are torn, the flags are freed, and hit the standard flag hard, which results in fertilization. Freeing of the genital organ from keel petals for fertilization and pollination is called tripping. Needless to say, tripping is not necessary for fodder production; it is only needed when seeding is intended.
E: Fruit: Alfalfa fruit is a twisting and spiral pod with kidney-shaped seeds. The seeds are in yellow or brownish yellow and 1000 seeds weight 2 to 3 grams. Propagation of alfalfa is via seeds, however, it can also be propagated asexually by slips, and stem cutting and root cutting. Growth vigor of alfalfa fruit is low when on alfalfa plant and it decreases sharply after 3 years, so it is better to use annual seeds for planting.
Alfalfa Ecology:
A: Suitable soil: Because alfalfa survive for 3 to 5 years, subject to climatic conditions of a region and as it becomes compressed and stiff owing to agricultural machinery movements in different growing and harvesting stages, therefore, alfalfa should be cultivated in soils crop depth of which is not less than 20 cm. Sandy clay and clay sandy soils are suitable for cultivation of this plant. Alfalfa is able to be cultivated in saline and calcareous soils. It grows best in the interval of neutral pH to slightly alkaline and is not able to grow in pH levels under 5.5.
B: Suitable weather: Alfalfa is highly adaptable to different climates, therefore, it is cultivated across the world. It survives cold temperatures from – 54 to -60 degrees Celsius provided that it is covered by snow. Favorable and optimal temperature for alfalfa is between 15 to 30 degrees Celsius.
Alfalfa planting:
As alfalfa survives for a long time and hence is cropped in several pickings or turns every year, then a prepared agricultural land is important for alfalfa. Because seed sizes are small, the seedbed need to be soft and the soil grains fine. Alfalfa can be planted in both Autumn and Spring; however, its Spring cultivation is a common routine. For Spring cultivation, land is plowed to a depth of 15 to 30 cm in the Autumn of the previous year. It is recommended to add 20 to 30 tons of rotten manure per hectare before that Autumn plowing. In the Spring, 1 or 2 weeks before sowing the seeds, a plow perpendicular to the main plow is performed and the land is disked.
It is better to use a trowel or special alfalfa spreaders for leveling. After preparing the land, cultivation of seeds takes place in two ways.
A: via hand-sowing: The worst type of cultivation of alfalfa is via hand-sowing because for lack of distribution of seeds, the seeds located 10 cm deep in the soil will never sprout.
B: Row seeding: In this case, alfalfa seeds are planted using row seeding. The distance between rows is 20 to 25 cm and the distance between seeds on rows is 3 to 4 cm. If the purpose is to prepare seeds, the distance between rows could be considered to be 60 to 90 cm.
To bury the seeds in hand-sowing way, a trowel or a rake is used. The amount of seeds used in hand-sowing way is 30 to 40 kg per hectare and in row seeding, 15 to 10 kg/ha. It is better to cultivate alfalfa in the form of a pyramid to reduce the problem of seeds movement. Alfalfa cultivation takes place as mixed with gramineous plants and grasses—esp. barley—in a ratio of 9 (alfalfa) to 1 (barley).
Mixed cultivation has advantages including:
1. As alfalfa does not produce much crop in the first year and the first pick, grass- gramineous plants are used.
2. In the Spring, grass grows earlier than alfalfa, so it protects young alfalfa plants from sunlight radiations.
3. Mixing alfalfa with grass is more palatable due to its high carbohydrate content.
4. When drying alfalfa crop is less damaged if is mixed with grass.
Fertilizer amount
1. Nitrogen: Among the needed fertilizers, Nitrogen is less frequently used, this is because of nitrogen fixation made by symbiotic bacteria (Rhizobium) during growth period which makes the plant able to provide their required nitrogen, however, 20-40 kg/ha Nitrogen is used as a starter fertilizer.
2. Phosphorus and potash: Depending on the needed soil, 100 to 150 kg/ha is consumed.
Note 3. As alfalfa survives for several years, so due to frequent irrigation, the soil becomes acidic after a few years and it is necessary to add lime to the field once in a few years to increase the pH and neutralize harmful acids.
Growing operations:
1. Replanting: In alfalfa farms, usually in the first year, empty spots are seen on the field surface for the following reasons:
A: Low alfalfa seed growth vigor, B: Uneven distribution of seeds in hand-sown planting, C: Non-emergence of seeds placed in the depths, D: Soil clogging, accompanying plant places left empty: Leaving these places empty gradually causes weeds to develop, therefore, after the first picking, sowing seeds is started in these places.
2. Fertilization: Besides the fertilizers added to the soil earlier and at planting stage, every year at the end of Autumn, potash or phosphorus fertilizers are used, upon the soil needs and in proportion to the crop that is going to be harvested annually from the soil.
3. Irrigation: Alfalfa is a plant that needs sufficient water to produce crop and crop is produced in proportion to the amount of water received. In general, the need for water in crops depends on the texture and structure of soil, level of rainfall, soil depth, and temperature. In alfalfa, it depends on the number of pickings harvested. For alfalfa, irrigations are done before planting and subsequent irrigations are done after seedling emergence and in early stage of growth at immediately lowered intervals and with low volume of water. By continuation of growth, irrigation intervals and the amount of water are increased. Alfalfa is irrigated 15-30 times a year; in temperate and cold regions it is irrigated once in every 8-10 days and in tropical regions once in every 4-6 days. Irrigation takes place in three ways:
A) Flood or plot irrigation: If the slope of the land is uneven, the farmer has to irrigate as such
B) Leakage or row irrigation: Used to prevent clogging
C) Rain-fed irrigation: In the first year, this type of irrigation may cause problems owing to soil compaction, however, since the second year, it has the following advantages: Saving water consumption, maintaining soil moisture, the possibility of distributing fertilizer in water.
4. Pest control against diseases and weeds: Alfalfa has a very slow growth in its early growth stage when weeds can overcome and not only delay alfalfa growth but also reduce the harvested fodder quality. The most important weed of Alfalfa fields is a flowering parasite plant called cuscuta. After growing, this plant wraps itself around the stem, disconnects it from the ground, and feeds on the elaborate sap of alfalfa with its sucking organs.
How to combat against cuscuta:
A) Prevention method: 1. Winnowing seeds: Alfalfa seeds are kidney shaped and smooth, while cuscuta seeds are almost round and uneven. Therefore, by mixing the seeds mass with iron powder and passing the seeds through a bug screening system equipped with a magnet, winnowing is performed, 2. avoid using contaminated manure, 3. avoid using contaminated water, and 4. Silt and weed removal
B) Agronomic control: 1- Carrying out crop rotation, 2- Creating a drought period, 3- Burning infected plants by flamethrowers
C) Chemical control:
1. Use 3-5 l/ha of ductal toxin before contact of cuscuta with alfalfa
2. Use 7-15 l/ha of ductal toxin after contact of cuscuta with alfalfa
3. Use general pesticides such as Randab Gramaxon to remove infected plants. Use of chemical pesticides is not recommended, as in addition to being expensive, they are hazardous for remaining in food chain. Therefore, the main point when planting is to have a weed-free field. Purity of seeds at the time of planting should be over 98% and the remaining 2% should not be cuscuta seeds. Orobanche is another weed in alfalfa field and to combat against it, orobanche flies could be used. Some weeds such as wild barley and wheat have thorns, and may injure livestock’s buccal mucosa when feeding. Some, such as bulbous grasses, cause their milk taste and smell to change. For pests, the most important pests of alfalfa is a brown to black colored beetle called hypera miner. In Winter this pest spends as an adult insect under weeds or in the soil and spawn on young stems after mating in Spring. Damage is caused by the larvae of this insect, which feeds on all leaves except the veins. To fight against this pest, first picking could be pushed forward and performed earlier or chemical pesticides such as diazinol and valendine van valerate could be used in early spring after the complete insect leaves its seed. Diseases as flax, leaf spot disease, root rot and nematodes pests could also be mentioned, the most important factor in combating against them is the use of resistant cultivars.
Hay harvest:
The most important factors to consider in harvesting alfalfa:
1. Yield 2. Fodder quality 3. The effect of harvesting on crop durability.
The time of harvesting alfalfa is an important factor in yielding high quality fodder. If harvesting is earlier than the scheduled times, the quality is high but the yield is low. If it is late, the quality is low and the yield is higher. The best time to harvest alfalfa is when 10-25% of the field is flowering. It should be noted that the alfalfa planted in Autumn should not be harvested in the first year, and the alfalfa planted in the Spring is to be harvested to strengthen the plant during its full flowering. The closer the time interval between pickings, the more damage affects the plant owing to low carbohydrate and nutrient storage. Therefore, alfalfa should never be harvested before reaching a height of 15-25 cm. At the time of harvesting alfalfa, the height of cutting from the soil surface should be 5-10 cm. It is better to harvest early in the morning; seeds are to be harvested when 75% of the pods are in dark color.
