The author conducted long-term research in rural areas and discovered that many farmers have misconceptions about fertilizer application. To help them use fertilizers more effectively, this article provides a brief overview of the properties and proper application methods of several commonly used fertilizers.
1. Main Types and Properties of Nitrogen Fertilizers
1.1 Ammonium Bicarbonate contains 17% nitrogen. When applied to the soil, it breaks down into NH₄⺠and HCO₃â», both of which can be absorbed by plants. It supplies both nitrogen and carbon dioxide, making it suitable as a basal fertilizer. However, it is not recommended for top-dressing due to its tendency to volatilize. To reduce loss, it should be applied at a depth of 7–10 cm and covered with soil. The best method is to apply it through furrows or holes and then cover thoroughly.
1.2 Urea contains 46% nitrogen, making it the most concentrated and highest-quality nitrogen fertilizer available. Once applied to the soil, it dissolves and converts into ammonium nitrogen. Urea is mostly not adsorbed by soil colloids, so it can easily leach away after heavy rain or flooding. Light rain or gentle irrigation after application is preferable. Urea is a neutral fertilizer, suitable for all types of soil and crops. It can be used as a seed fertilizer, base fertilizer, top dressing, or foliar spray. However, it should not come into direct contact with seeds to avoid burning, and the dosage must be carefully controlled. Urea is especially effective for top dressing, with concentrations ranging from 0.5% to 1.0%, depending on the crop type. For example, grasses, radishes, cabbages, and cucumbers require higher concentrations, while sweet potatoes, potatoes, watermelons, eggplants, peanuts, and tomatoes need lower ones. Apply evenly to leaves in the morning or evening. Urea can also be mixed with potassium dihydrogen phosphate, ammonium phosphate, phosphate fertilizers, insecticides, and fungicides for combined nutrient supply and pest control.
1.3 Ammonium Nitrate contains 33–35% nitrogen and appears as white crystals. It is more suitable for dry fields than paddy fields.
2. Main Types and Properties of Phosphate Fertilizers
2.1 Superphosphate (also called calcium superphosphate) mainly consists of water-soluble calcium phosphate, containing 12–20% phosphorus pentoxide. Phosphorus tends to be fixed by the soil and has very limited mobility, usually remaining within 0.5 cm of the application point. Therefore, concentrated application—such as in furrows or holes—is an efficient method to maximize its effectiveness. This reduces the contact area between the fertilizer and the soil, minimizing phosphorus fixation. It can also be combined with organic fertilizers to further reduce fixation and improve efficiency. Superphosphate can be used as a base fertilizer, top dressing, seed fertilizer, or side dressing. For base fertilizer, deeper placement is more effective. When used as a seed fertilizer, the concentration should be 1–2% for monocots and 0.5–1% for dicots.
2.2 Heavy Superphosphate (also known as triple superphosphate) contains water-soluble monocalcium phosphate, with a higher concentration of phosphorus pentoxide (36–54%). It is two to three times more concentrated than regular superphosphate. Its usage is similar to that of ordinary superphosphate.
Author: Tianjin Wuqing District Agricultural Technology Promotion Center
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