As agriculture advances, crop nutrient needs are becoming more diversified. Building on our previous discussion, this article delves into the types, characteristics, and application strategies for micronutrient and compound fertilizers.
I. Micronutrient Fertilizers: Small but Essential
Micronutrient fertilizers contain small yet essential elements like boron (B), manganese (Mn), molybdenum (Mo), zinc (Zn), copper (Cu), and iron (Fe). Although present in minor quantities, these elements are critical for crop health and yield. In recent years, micronutrient deficiencies have become common in various crops, with maize and rice often deficient in zinc, fruit trees lacking iron and boron, and rapeseed in need of boron. Proper application of micronutrient fertilizers can effectively enhance crop growth, yield, and economic returns.
Main Types of Micronutrient Fertilizers and Application Recommendations
Boron Fertilizers
Types and Properties: Common boron fertilizers include borax and boric acid, widely used in boron-deficient areas.
Application: The amount of boron fertilizer depends on crop and soil needs. Crops with high boron demands, such as rapeseed, sugar beets, and cotton, should be prioritized. Boron is effective in soils with water-soluble boron content below 0.5 mg/kg. Apply 0.25-0.5 kg of borax or boric acid per 667 square meters, avoiding over-application to prevent toxicity. Seed soaking or coating should use a concentration of 0.01%-0.1%.
Zinc Fertilizers
Types and Properties: Zinc sulfate and chelated zinc are commonly used, with zinc sulfate showing high absorption efficiency in field conditions.
Application: Zinc fertilizers are highly effective for zinc-sensitive crops like maize and rice, particularly where soil zinc levels are below 0.5 mg/kg. Apply 1-2 kg of zinc sulfate per 667 square meters as a basal fertilizer. For foliar application, use a concentration of 0.1%-0.5%.
Manganese Fertilizers
Types and Properties: Manganese sulfate and manganese chloride are effective in improving yields for manganese-sensitive crops such as legumes and wheat.
Application: In soils with low manganese, foliar application of a 0.05%-0.1% manganese solution is highly effective.
Iron Fertilizers
Types and Properties: Ferrous sulfate is a common iron fertilizer, suitable for crops with iron deficiency, such as fruit trees and soybeans.
Application: Foliar spray of 0.5%-1% ferrous sulfate solution helps alleviate chlorosis due to iron deficiency. Adding a small amount of urea and citric acid can enhance effectiveness.
Molybdenum Fertilizers
Types and Properties: Commonly used molybdenum fertilizers include ammonium molybdate and sodium molybdate, particularly beneficial for legumes and rapeseed.
Application: Before sowing, treat legume seeds with 2-6 grams of ammonium molybdate per kilogram of seed. Foliar application at 0.01%-0.1% is effective for crops with large leaf areas.
Copper Fertilizers
Types and Properties: Copper sulfate is a widely used copper fertilizer, particularly effective for high-copper-demand crops like wheat, carrots, and sunflowers.
Application: Apply 1-1.5 kg of copper sulfate per 667 square meters as a basal fertilizer. Due to copper's long retention in soil, it is usually applied every 3-5 years.
Key Considerations for Micronutrient Fertilizer Application
Control Dosage and Concentration: The required amount of micronutrients is minimal; over-application may lead to toxicity or environmental pollution.
Optimize Soil Conditions: Adjusting soil pH and organic matter levels can increase the bioavailability of micronutrients.
Combine with Major Nutrients: Micronutrients should be used alongside nitrogen (N), phosphorus (P), and potassium (K) to maximize fertilizer efficiency.
II. Compound Fertilizers: A Balanced Nutrient Solution
Compound fertilizers are those that contain two or more essential nutrients, such as nitrogen (N), phosphorus (P), and potassium (K), in a single product. When a fertilizer includes two primary nutrients, it is called a binary compound fertilizer; if it contains three, it is known as a ternary compound fertilizer, and with more than three, it is termed a multinutrient compound fertilizer.
Types of Compound Fertilizers and Production Processes
Chemically Formed Compound Fertilizers: Made through chemical reactions, such as monopotassium phosphate.
Mixed Compound Fertilizers: Produced by processing multiple single-element fertilizers together, commonly referred to as blended fertilizers. Some chemical reactions may occur during processing.
Mechanically Blended Compound Fertilizers: Created by mechanically mixing different fertilizers without chemical reactions, such as ammonium phosphate.
Advantages and Disadvantages of Compound Fertilizers
Advantages: High concentration of active ingredients, comprehensive nutrients, minimal adverse effects on soil, and relatively low cost.
Disadvantages: Fixed nutrient ratios, making it challenging to meet the specific needs of various soil types and crops. Compound fertilizers require specific application techniques, as different nutrients have unique absorption patterns and must be adapted based on soil and crop characteristics.
Major Types of Compound Fertilizers and Recommended Application
Ammonium Phosphate
Features: Produced by neutralizing phosphoric acid with ammonia, with nitrogen content around 14%-18% and phosphorus 46%-50%. It dissolves easily and is suitable for crops requiring higher phosphorus.
Application: Used as a base or top dressing, with 10-15 kg per 667 square meters. Avoid using with alkaline substances like wood ash to prevent nitrogen loss.
Ammoniated Superphosphate
Features: Created by adding ammonia to superphosphate, with nitrogen content 2%-3% and phosphorus 13%-15%. Ideal for acidic soils, offering stable properties and better efficacy than regular superphosphate.
Application: Use as a base or top dressing, and avoid mixing with alkaline substances to prevent nitrogen loss.
Monopotassium Phosphate
Features: A high-concentration, phosphorus-potassium binary compound fertilizer, with nutrients at 0-52-34. It has low moisture absorption and good solubility.
Application: Suitable for seed soaking and foliar spraying at 0.2%-0.5% during critical growth stages to improve crop quality.
Potassium Nitrate
Features: Known as saltpeter, with nitrogen at 13% and potassium at 46%. Suitable for potassium-loving crops that avoid chlorine, such as potatoes. It has high efficacy and is water-soluble but should be handled carefully due to flammability.
Application: Ideal for top dressing in dryland crops, with 5-10 kg per 667 square meters. For foliar spray, keep the concentration at 0.6%-1%.
Urea Ammonium Phosphate
Features: A combination of urea and ammonium phosphate with a nitrogen-to-phosphorus ratio of either 1:1 or 2:1, suitable for various crops.
Application: Best used with single-element fertilizers to maximize effects. Applied as a base or top dressing similarly to ammonium phosphate.
Ammonium Phosphorus Potassium Fertilizers
Features: A ternary compound made from ammonium sulfate, potassium sulfate, and phosphate salts. Common ratios include 12-24-12, 10-20-15, or 10-30-10, suited to potassium-demanding crops like tobacco.
Application: Adjust application based on soil and crop needs, supplementing with nitrogen or potassium as required.
Scientific Application of Compound Fertilizers
Apply According to Soil and Crop Needs: Choose the type of compound fertilizer that aligns with soil composition and crop nutrient requirements.
Optimize Nutrient Distribution: Use appropriate ratios of nitrogen, phosphorus, and potassium for crops with different nutrient demands.
Avoid Over-Application: Follow recommended dosages to prevent nutrient waste and soil pollution.
Using compound fertilizers correctly can significantly boost crop yield and quality, promoting efficient and sustainable agricultural production.
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