Forage characteristics

Alfalfa, a perennial leguminous grass, has strong stress resistance and a wide range of adaptability, and can grow in various types of climate and soil environments. It prefers a dry, warm climate with many sunny days and few rainy days and a dry, loose, well-drained soil rich in calcium. The optimum temperature is 25 to 30°C; it grows well where the annual rainfall is 400 to 800 mm, but it grows poorly when it exceeds 1,000 mm. The annual rainfall is within 400 mm, and irrigation conditions are required to grow vigorously. The rainy, humid and hot weather in summer is the most unfavorable. Alfalfa has a high transpiration coefficient and requires a lot of water for growth. Approximately 800 grams of water are needed to make up 1 gram of dry matter, but water accumulation is the most avoidable. If it is continuously flooded for 1 to 2 days, a large number of people will die. Alfalfa is suitable for planting in neutral to slightly alkaline soil, but is not suitable for strongly acidic or alkaline soil. The optimal soil pH value is 7 to 8, and it can grow when the soil contains soluble salts below 0.3%. Areas below 2,700 meters above sea level, with a frost-free period of more than 100 days, annual accumulated temperatures of ≥10°C and above 1,700°C, and annual average temperatures above 4°C are suitable areas for alfalfa planting. Alfalfa is a plant affected by strong light. The maximum amount of carbon dioxide that newly developed leaves can assimilate is 70 mg per square meter per hour. The starch content of leaves changes greatly day and night, with the dry weight increasing from 8% in the morning to 20% at sunset. Afterwards, the content dropped sharply. Leaves are the place for photosynthesis. The leaf area index of a well-developed alfalfa population is usually 5, with 5,000 to 15,000 medium-sized leaves per square meter.

Cultivation Technology

(1) Soil Tillage and Fertilization Alfalfa has small seeds, weak buds, and poor soil support. Soil preparation must be meticulous, requiring flat ground, finely crumbled soil, and no Weeds, good moisture. Alfalfa has a well-developed root system and penetrates deep into the soil. The sowing land must be plowed deeply to allow the roots to fully develop. Alfalfa has a long growth life, is cut and utilized many times a year, and absorbs a lot of nutrients from the soil. According to reports, alfalfa absorbs 13.3 kilograms of nitrogen, 4.3 kilograms of phosphorus, and 16.7 kilograms of potassium per acre per year. Nitrogen and phosphorus are 1 to 2 times more than wheat, and potassium is 3 times more. The land used for sowing alfalfa should be lightly plowed to remove stubble and plowed deeply after harvesting the previous year. In winter and spring, raking, water storage and moisture conservation should be done. The irrigated land should be filled with enough winter water. Before sowing, shallow plowing or harrowing should be carried out to prepare the land. Combined with deep plowing or shallow plowing before sowing, apply 1500 to 2500 kilograms of organic fertilizer per acre and 20 to 30 kilograms of superphosphate as base fertilizer. For soils with low fertility, apply quick-acting nitrogen fertilizers such as ammonium nitrate during sowing to promote seedling growth. Top dressing should be carried out after each mowing, and 10 to 20 kilograms of superphosphate or 4 to 6 kilograms of phosphorus diamine are required per acre.

(2) Sowing 1. seed. The seeds should be sun-dried for 2 to 3 days before sowing to break dormancy and improve the germination rate and seedling uniformity. Seed fields must be sown with Grade I seeds specified in national or provincial pasture seed standards; grassland can be sown with Grade I, II, or III seeds. 2. Vaccination. When sowing in land that has never been planted with alfalfa, it is necessary to inoculate alfalfa rhizobia. Use 5 grams of inoculant per kilogram of seeds to make a bacterial solution and sprinkle it on the seeds. Stir thoroughly and mix as you go. When using a sterile agent, mix old alfalfa soil and seeds with a ratio of at least 1:1. 3. Seeding rate. For seed fields, 3.75 to 7.5 kilograms per hectare, for grassland, 11.25 to 15 kilograms per hectare. In arid, hillside or alpine areas, the seeding rate is increased by 20 to 50%. 4. Sowing period. Due to the different climates in different parts of Gansu, it can be divided into three situations: spring sowing. After the ground thaws in spring, sow seeds at the same time as spring sown crops. Spring sown alfalfa will develop well that year and yield high yields, so seed fields should be sown in spring. Summer sowing. When there is drought in spring in arid areas and soil moisture is poor, sowing can be done after the summer rains. Autumn sowing. In northern my country, autumn sowing cannot be later than mid-August, otherwise the overwintering rate of seedlings will be reduced. 5. Sowing depth. Depending on soil moisture and texture, dry soil should be deeper, wet soil should be shallower, loamy soil should be deeper, and heavy clay soil should be shallower, generally 1 to 2.5 cm. 6. Sowing method. Commonly used sowing methods for alfalfa include drill sowing, broadcast sowing and hole sowing; sowing methods include single sowing, mixed sowing and protected sowing (cover sowing). It can be selected according to the specific situation. Seed fields should be sown individually, in holes or in wide rows, with row spacing of 50 cm, hole spacing of 50 × 70 cm or 50 × 50 cm or 50 × 60 cm, and 1 to 2 seedlings in each hole. The harvested grassland can be drilled or broadcasted, single or mixed sown or protected sown. The spacing between sowing rows is 30 cm. When sowing, plow lightly first, sow the seeds, and then rake.

Mixed sowing can be broadcast or drilled, drilled in rows or interrowed. For protection sowing, it is necessary to drill or broadcast to protect the crops first, then sow alfalfa seeds, and then rake. Protected sowing can be used in irrigated areas and areas with good water and fertilizer conditions. Protected crops include wheat, rapeseed or oats, grass sorghum, grass millet, etc. However, the protected crops should be harvested as early as possible. When carrying out protected sowing in arid areas, not only will the yield of alfalfa that year be low, but it will even affect the harvest of the next year. It is best to practice sowing alone in spring. In mixed sowing, alfalfa grows quickly, has many tillers, abundant branches and leaves, high yield, strong regeneration, and frequent mowing. It is difficult for other forages to cooperate in mixed sowing, so it is better to sow alone. However, if you want to improve the nutritional value, palatability and winter survival rate of pasture, mixed sowing can also be used. Pastures suitable for mixed sowing include: chickenfoot grass, cattail grass, perennial ryegrass, goosegrass, smooth brome, etc. The appropriate proportion of mixed sowing is alfalfa accounting for 40% to 50%. (3) Field management 1. After sowing but before seedlings emerge, if the soil becomes hardened due to rain, the hardened layer should be removed promptly to facilitate seedling emergence. 2. The growth in the seedling stage is very slow and it is susceptible to weed damage. It needs to be cultivated and weeded 1 to 2 times. 3. In the year of sowing, before the end of the growing season, cut and utilize it once. When the height of the plant cannot reach the utilization level, the seedlings must be kept for the winter. Grazing is strictly prohibited in winter. 4. For alfalfa fields older than two years old, the remaining stubble in the field should be cleared before germination every spring, and the cultivated land should be protected and harvested. After the last mowing and harvesting in autumn, the soil should be loosened and topdressed. After each mowing, the ground should be raked and topdressed, and the irrigated area should be topdressed with water. In winter, sufficient winter water should be poured. 5. The height of alfalfa cutting stubble is 3 to 5 centimeters, but in arid and cold areas, the height of the last cutting stubble in autumn should be 7 to 8 centimeters to maintain root nutrients and facilitate winter snow accumulation, which is good for overwintering and spring germination. effect. 6. The last mowing in autumn should be completed 20 to 30 days before the end of the growing season. Too late is not conducive to the accumulation of nutrients in the roots and rhizomes of the plant. 7. Seed fields should be pollinated manually or by bees during the flowering period to increase the seed setting rate. 8. There are many diseases and insect pests in alfalfa. Common diseases and insect pests include downy mildew, rust, brown disease, etc., which can be controlled by Bordeaux mixture, stone flow mixture, thiophanate, etc. Insect pests include aphids, dust bugs, blind bugs, scarabs, etc. It can be controlled with dimethoate, trichlorfon and other drugs. However, it is advisable to mow and feed livestock as soon as pests and diseases are discovered.