The author conducted long-term field research in rural areas and found 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 dissociates 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 ideal for top-dressing due to its high volatility. To reduce losses, it should be applied at a depth of 7–10 cm and covered with soil immediately. The best method is to apply it through furrows or holes and then cover tightly with soil.
1.2 Urea has the highest nitrogen content at 46%, making it one of the most concentrated nitrogen fertilizers. Once dissolved in the soil, it initially exists in a molecular form before converting to ammonium nitrogen. Urea is not easily adsorbed by soil colloids, so it can be lost after heavy rain or flooding. Light rainfall or irrigation after application is recommended. Being neutral, it can be used on all types of soil and crops. It can be applied as a seed fertilizer, base fertilizer, top-dressing, or foliar spray. However, it should not come into direct contact with seeds to avoid burning. The recommended concentration for top-dressing is 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 amounts. Apply evenly on leaves during early morning or late evening. Urea can also be mixed with potassium dihydrogen phosphate, ammonium phosphate, phosphate fertilizer, insecticides, and fungicides for combined nutrient and pest control benefits.
1.3 Ammonium Nitrate contains 33% to 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% to 20% P₂O₅. Due to its low mobility, phosphorus tends to be fixed in the soil, mostly within 0.5 cm of the fertilizer placement. Therefore, concentrated application—such as through drilling or furrowing—is an effective way to maximize efficiency. This method reduces the contact area between the fertilizer and soil, minimizing phosphorus fixation. Combining it with organic manure can further reduce fixation and improve fertilizer efficiency. Superphosphate can be used as a base fertilizer, top-dressing, seed fertilizer, or foliar application. As a basal fertilizer, deeper placement gives better results. For monocots, the concentration should be 1% to 2%, while dicots require 0.5% to 1%.
2.2 Triple Superphosphate (also known as heavy superphosphate) contains 36% to 54% Pâ‚‚Oâ‚…, primarily in the form of water-soluble monocalcium phosphate. It is a high-concentration phosphate fertilizer and is used similarly to regular superphosphate.
Author: Tianjin Wuqing District Agricultural Technology Promotion Center
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