2026/07/10
Answer: The utilization rate of phosphate fertilizer in the current season is generally only 10% to 25%, making it the lowest among the three major fertilizers. The fundamental reason is the extremely poor mobility of phosphorus in the soil—phosphorus mainly moves by diffusion, typically traveling only 1 to 3 centimeters after application, with the vast majority concentrated within 0.5 centimeters of the application point. Simultaneously, soluble phosphorus is largely adsorbed and fixed after entering the soil, gradually transforming into chemically fixed forms, converting available phosphorus into insoluble phosphorus, a process that can last for months or even years. In acidic soils of the south, phosphorus easily combines with iron and aluminum ions to form insoluble iron phosphate and aluminum phosphate; in calcareous soils of the north, it combines with calcium ions to form insoluble calcium phosphate. This is the core reason for the inefficient use of phosphate fertilizer.
To improve the utilization rate of phosphate fertilizer due to its fixation characteristics, two main principles should be followed: reduce the contact between fertilizer and soil to avoid fixation, and increase the contact between fertilizer and roots to facilitate absorption. Specifically, the following measures can be taken:
1. Concentrate application to reduce the contact area. Phosphate fertilizer has very low mobility in soil, and broadcasting it will cause a large area of phosphorus to be fixed. It should be applied in a concentrated manner, such as furrow application, hole application, seed coating, or root dipping, placing the phosphate fertilizer in the dense root layer of the soil to reduce the contact area between the phosphate fertilizer and the soil, thus reducing fixation. In paddy fields, this method can be used by stuffing seedlings with seedling bags or dipping seedling roots. Phosphate fertilizer is generally best applied as a base fertilizer and should be avoided as a top dressing.
2. Mixing and composting with organic fertilizer utilizes organic acids to complex and fix ions. Mixing phosphate fertilizer with organic fertilizer is an effective measure to reduce soil fixation. On the one hand, organic colloids and coarse organic matter can protect water-soluble phosphates, preventing them from directly contacting ions such as iron, aluminum, and calcium; on the other hand, organic acids produced during the decomposition of organic matter can form complexes with iron, aluminum, and calcium ions in the soil, thereby reducing the formation of insoluble phosphates. It is recommended to mix phosphate fertilizer with well-rotted organic fertilizer in a certain proportion, compost it, and then apply it to the soil.
3. Foliar fertilization (foliar spraying) bypasses soil fixation. Foliar fertilization can completely prevent phosphorus fixation in the soil. In the later stages of crop growth, when root nutrient absorption capacity weakens, foliar spraying with superphosphate leachate allows leaves to directly absorb phosphorus, resulting in lower fertilizer usage, faster effect, and higher utilization. The typical spraying concentration is: 0.5%–1% for dicotyledonous crops and 1%–2% for monocotyledonous crops.
IV. [Production Recommendations] How to improve phosphorus availability through fertilizer production processes?
We recommend the following optimization measures in compound fertilizer production lines:
Granular Production:Making phosphate fertilizer into 3–5 mm granules effectively reduces the contact area between phosphate fertilizer and soil, achieving the same phosphorus fixation reduction effect as concentrated application.
Phosphorus Activation Treatment:Adding chemical phosphorus activators can increase soil available phosphorus by 29.0%–49.0%, extending the effective period from approximately 35 days to over 65 days.
Controlled-release coating technology: Applying coated phosphate fertilizer in combination with ordinary phosphate fertilizer can significantly reduce fertilizer application and improve the current season's phosphorus utilization rate.
Precise formulation design: Utilizing an automatic batching system to precisely control the nitrogen, phosphorus, and potassium ratio allows for the combined application of nitrogen, phosphorus, and potassium—experiments show that this combination increases yield by 16.5% compared to phosphorus application alone.
Water and fertilizer integration adaptation: For drip irrigation systems, polyphosphate phosphorus sources (such as ammonium polyphosphate) are selected, as their mobility in the soil is superior to orthophosphate, improving the range of phosphorus transport and utilization.
Although the current season's phosphate fertilizer utilization rate is low, its residual effect is long-lasting—the cumulative utilization rate over 20 years can reach 38.9%. Therefore, phosphate fertilizer management should consider both current season utilization and the long-term cultivation of the soil's phosphorus pool.
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