1. Ammonium nitrogen fertilizer
The nitrogen in the fertilizer mainly exists in the form of ammonium (NH4+). The ammonia nitrogen fertilizer mainly includes ammonium sulfate, ammonium chloride, ammonium hydrogencarbonate, ammonia water and liquid ammonia.
Ammonia nitrogen fertilizer is easily soluble in water, and ammonium ions are formed after dissolution (chemical symbol is NH4+, the upper right corner plus sign indicates that ammonium ion has a positive charge), and ammonium ions can be directly absorbed and utilized by crop roots;
Ammonium ions can be adsorbed by negatively charged soil colloids, so they are not easily lost with water and are suitable for use in paddy fields;
Ammonia nitrogen fertilizer can be converted into nitrate nitrogen under the action of microorganisms in the soil, which can also be absorbed and utilized by crops;
When ammonia-nitrogen fertilizers encounter lime, grass ash or other alkaline fertilizers, ammonium will become a loss of ammonia volatilization. Therefore, it cannot be mixed with alkaline substances;
High concentrations of ammonium ions are toxic to crops, especially to seedlings;
It has an antagonistic effect on absorption of calcium, magnesium and potassium.
2. Nitrate nitrogen fertilizer
Nitrogen in nitrate nitrogen fertilizer exists in the form of nitrate ion (NO3-). The ammonia nitrogen fertilizer mainly includes potassium nitrate, calcium nitrate, ammonium nitrate and sodium nitrate.
The nitrate nitrogen fertilizer is easily soluble in water, and forms nitrate ions after dissolution (the chemical symbol is NO3-, and the minus sign in the upper right corner indicates that the nitrate ion has a negative charge), which can be absorbed and utilized by the crop roots;
Nitrate ions can not be adsorbed by negatively charged soil colloids, and are easily lost with water, so they should not be used in paddy fields, generally used in dry land;
In the soil under anoxic conditions, nitrate-nitrogen fertilizer will produce denitrification, which will convert nitrate nitrogen into nitrous oxide or nitrogen loss;
Nitrate nitrogen fertilizer has strong hygroscopicity and combustion support, flammable and explosive, and should pay attention to moisture and fire prevention during transportation;
The nitrate nitrogen fertilizer has a low nitrogen content;
Nitrate nitrogen fertilizer can promote the absorption of calcium, magnesium and potassium.
3. Amide nitrogen fertilizer
Nitrogen exists in the form of an amide group, and the common amide nitrogen fertilizer is urea.
Urea has a high nitrogen content and a nitrogen content of 46%.
Soluble in water, neutral, and can be mixed with most fertilizers;
After being dissolved in the soil, most of it can not be directly absorbed by the crop, and it needs to be converted into ammonium nitrogen before it can be absorbed by the crop. Therefore, in the low temperature season, the fertilizer effect is slower than that of ammonium nitrogen and nitrate nitrogen, and should be used in advance.