Nitrogen Fertilizer: Functions and Selection Methods Explained

Nitrogen fertilizer refers to a single-nutrient fertilizer that has nitrogen (N) as its main component, carries a stated N content, and, when applied to soil, can provide plants with nitrogen nutrition. In agricultural production, plant growth is inseparable from nitrogen fertilizer. Let's take a look below at what nitrogen fertilizer does and how to choose it.

1. What does nitrogen fertilizer do?

The effect of nitrogen on plant growth and development is very obvious. When nitrogen is sufficient, plants can synthesize more protein and promote cell division and expansion, so the leaf area of plants grows quickly and there is more leaf area available for photosynthesis.

In addition, the abundance or deficiency of nitrogen is closely related to the chlorophyll content in the leaves. The supply status of nitrogen nutrition can be judged from the size of the leaf area and the depth of leaf color. At the seedling stage, nitrogen deficiency in general plants usually appears as slow growth, short and small plants, thin and small leaves, and leaves that lack green and turn yellow. Gramineous crops show few tillers. When nitrogen is severely deficient in the later growth stage, it appears as short and small ears and shriveled grains. After increasing the application of nitrogen fertilizer, there is an obvious effect on promoting robust plant growth. Often after application, the leaf color quickly turns green and growth increases.

2. How to choose nitrogen fertilizer?

There are many varieties of nitrogen fertilizer, and according to compound form they can be divided into ammonium nitrogen fertilizer, nitrate nitrogen fertilizer and amide nitrogen fertilizer. Ammonium nitrogen fertilizers include ammonium bicarbonate, ammonium sulfate, ammonium chloride, ammonia water, liquid ammonia, etc.; nitrate nitrogen fertilizers include ammonium nitrate, sodium nitrate, calcium nitrate, etc.; amide nitrogen fertilizers include urea, calcium cyanamide (lime nitrogen), etc. In order to improve the application effect of nitrogen fertilizer, scientifically choosing the variety of nitrogen fertilizer is very important.

Generally speaking, crops with high carbohydrate content such as potatoes are suitable for the application of ammonium nitrogen fertilizer. For cereal crops such as wheat and corn, ammonium nitrogen and nitrate nitrogen are equally effective, but in rainy areas, in order to prevent nitrogen leaching loss, it is still advisable to apply ammonium nitrogen fertilizer.

For rice fields, urea and ammonium chloride are better choices, while ammonium sulfate and nitrate nitrogen fertilizers should not be chosen. This is because sulfate radicals are easily reduced to hydrogen sulfide in flooded fields, making rice roots black or even rot, and nitrate radicals are easily leached away with water in flooded fields and undergo denitrification, causing nitrogen loss.

For fiber crops such as hemp, ammonium chloride is preferable, because chloride ions can increase the toughness and tensile strength of the fiber. For tobacco, a combined application of nitrate nitrogen and ammonium nitrogen works well; nitrate nitrogen can improve the combustibility of tobacco, while ammonium nitrogen can promote the formation of aromatic volatile oils in tobacco leaves and increase the aroma of tobacco. Therefore, the combined application of these two forms of nitrogen fertilizer can improve its quality.

Applying ammonium sulfate on sulfur-deficient soil helps improve the sulfur nutrition of crops. Ammonium chloride, however, should not be applied to chlorine-sensitive crops that are sensitive to chloride ions, such as tobacco, grapes, potatoes, sweet potatoes, sugar beets, citrus, tea, sugarcane, watermelons and melons, otherwise their yield and quality will be significantly affected.