The hazards of excessive fertilization and soil improvement guidelines

In agricultural production, fertilization is an important means to increase crop yield, but blindly excessive fertilization not only fails to achieve the goal of increasing yield, but also leads to a series of problems such as soil nutrient accumulation and soil fertility decline, seriously affecting the sustainable development of agriculture. This article will provide a detailed analysis of the mechanism of nutrient accumulation in fertilizers, the multiple obstacles caused by excessive fertilization, and targeted soil improvement and prevention measures, providing scientific fertilization references for growers.
1、 Mechanism of nutrient accumulation in fertilizers
Once continuous cropping is implemented, fertilizer components will inevitably accumulate in the soil. This is because the fertilizer used for fertilization is not completely absorbed by the crops.

Flow direction of fertilizer components
Assuming a fertilizer application rate of 100, crops will absorb approximately 70% nitrogen, 20% phosphoric acid, and 80% potassium, and the remaining nutrients will accumulate in the soil.
In soil, most of the nitrogen is absorbed by bacterial cells and becomes organic matter; Phosphoric acid will combine with iron and aluminum, becoming insoluble in water. The fertilizer components remaining in the soil do not accumulate all at once, but gradually accumulate.
In addition, when applying compost, the components contained in the compost will also enter the soil; When planting vegetables with fast growth rates, people often apply excessive fertilizers to increase yields. Excessive accumulation of nutrients can lead to stunted growth of crop roots, resulting in poor crop growth conditions. Many people, in order to solve this problem, apply more fertilizers, thus falling into a vicious cycle.
2、 Obstacles caused by excessive fertilization
By applying sufficient compost, the buffering function of the soil can be enhanced; If high fertilizer cultivation is continued without applying compost, the soil fertility will significantly decline.
If there is too much nitrogen fertilizer, the soil will accumulate a large amount of nitric acid, causing the pH value of the soil to decrease and gradually becoming abandoned land. Excessive use of nitrogen fertilizer can also cause gas hazards:
Excessive application of urea fertilizer in dry fields can produce nitrous oxide and ammonia gas in an oxidized state; Excessive application of ammonium sulfate in paddy fields can cause sulfate ions to dissociate in a reduced state, producing hydrogen sulfide gas.
3、 Accumulate faster in facility cultivation
Under open-air cultivation, nitrogen and potassium will be lost with rainwater, but in facility cultivation, salts will accumulate more rapidly because they will not be lost due to rainwater.
In facility cultivation, excessive application of fertilizers leads to the accumulation of salts, causing the soil to become high salt soil and disrupting the balance of microorganisms. When salt accumulates, ammonia gas will be produced in alkaline soil with a pH value above 7; When nitric acid accumulates, acidic soil with a pH value below 5 will produce nitrous acid gas, which can cause damage to crops and affect the normal growth of leaves or fruits.

The harm of excessive fertilization in facility cultivation
4、 How to prevent excessive accumulation of nutrients
The methods to prevent salt accumulation include reducing the amount of application and seizing the accumulated nutrients.

（1） Reduce the application amount according to the results of soil diagnosis, avoid excessive fertilization, and carefully choose the type of fertilizer, using urea or ammonium nitrate fertilizers that do not contain sulfur ions in their composition. In addition, when applying organic matter, it is necessary to avoid livestock manure compost with high fertilizer content, and only apply a moderate amount of mixed bark compost with low fertilizer content. （2） Extracting nutrients to remove crop residues from farmland, further planting grass suppressing crops such as sorghum that can absorb a large amount of fertilizer components, and finally removing these crops from farmland. In emergency situations, flooding and desalination can be carried out, which means flooding with water to wash away fertilizer components.