Nitrogen is a crucial element for the growth and development of alfalfa. Proper nitrogen application enhances plant vigor, delays flowering, and can improve cold resistance. When nitrogen levels are adequate, the plant exhibits strong growth, with large branches and leaves, moderate flowering, and high fruit yield. However, excessive nitrogen can lead to overly long shoots and large fruits, but with poor color, taste, and firm flesh. On the other hand, nitrogen deficiency results in weak growth, short and thin shoots, small and thin leaves, early leaf drop, and reduced fruit production.
Phosphorus is highly concentrated in the reproductive parts of alfalfa. Applying phosphorus improves fruit set, stimulates root development, and increases sugar content in fruits. A phosphorus-deficient plant shows poor root growth, small leaves, dark green coloration, and overall stunted growth.
Potassium is abundant in the fruits and also present in high amounts in leaves and shoots. Potash fertilizer significantly promotes fruit enlargement and improves fruit quality. It also helps in better branch development and enhances the plant's resistance to diseases.
Calcium is the most plentiful mineral in the plant. It helps regulate the tree’s internal pH. Alfalfa grows vigorously in calcium-rich soils. In calcium-deficient conditions, buds may turn brown and die.
Magnesium is an essential component of chlorophyll. A lack of magnesium causes yellowing between the leaf veins, leading to premature leaf drop. Overall, the nutrient composition of dry alfalfa matter includes 0.71% calcium, 0.53% potassium, 0.39% nitrogen, 0.10% magnesium, and 0.06% phosphorus. Other elements like sodium, iron, manganese, zinc, and boron are also present. Iron has the highest concentration, ranging from 126 to 700 mg per 100 g, followed by potassium at 210 mg per 100 g.
Normal alfalfa leaves typically contain 1.35% nitrogen, 0.09% phosphorus, 0.4% potassium, 0.16% calcium, and 0.05% magnesium. If any of these values fall below the standard, it indicates a deficiency in that particular nutrient. Therefore, leaf analysis serves as a reliable method for determining the need for fertilization and ensuring optimal growth conditions for alfalfa.
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