Types of fertilizers and nitrogen fertilizers applied

1. Ammonium bicarbonate: the molecular formula is NH4HCO3, which contains about 17% nitrogen. It is a white crystal with unstable chemical properties, easy to absorb moisture and decompose, easy to volatilize, strong pungent, fumigating ammonia smell, the greater the humidity, the higher the temperature, the faster the decomposition, the easier to dissolve in water, showing an alkaline reaction (pH8.2-8.4). Ammonium bicarbonate is an unstable compound, which decomposes completely at atmospheric pressure and temperature up to 70 ℃. When the temperature is 20 ℃, the loss rates of 1 day, 5 days and 10 days are 9%, 48% and 74%, respectively. It is easy to absorb moisture, dissolve and agglomerate in a humid environment (caking itself is a sign of slow decomposition). In the process of storage and application, corresponding measures should be taken to prevent its volatilization loss. Suitable for all kinds of soil and crops, it is suitable to be used as base fertilizer, and attention should be paid to deep covering soil when topdressing. 2. Urea: the molecular formula is (NH2) 2CO, which contains about 46% nitrogen. Common urea is white crystal and has strong hygroscopicity. At present, most of the urea produced are translucent particles and have been treated with anti-moisture absorption. When the temperature is 10-20 ℃, the hygroscopicity is weak, and with the increase of air temperature and humidity, the hygroscopicity increases. Urea is a neutral fertilizer, long-term application has no side effects on the soil. After being applied to the soil, it is easy to be hydrolyzed into ammonium carbonate by the action of urease secreted by soil microorganisms and absorbed by crops. The hydrolysis process is as follows: (NH2) 2CO+2H2O → (NH4) 2CO3 hydrolysis rate is related to soil acidity, humidity and temperature, and also affected by soil type, maturity and fertilization depth. In general, the time for urea to hydrolyze into ammonium carbonate is about 10 days at 10 ℃, 4-5 days at 20 ℃, and 2 days at 30 ℃. Therefore, the fertilizer effect of urea is relatively slow, and topdressing should be made in advance. Urea is suitable for all kinds of soil and crops, and can be used as base fertilizer, topdressing and foliar spraying (spraying concentration is 1-2%). 3. Ammonium chloride: the molecular formula is NH4Cl, containing 24-25% nitrogen, white crystal, soluble in water, low hygroscopicity, no caking, good physical shape, easy to store. Ammonium chloride is acidic and is also a physiologically acidic fertilizer. Ammonium chloride should not be applied to acid soil, saline-alkali soil and chlorine-avoiding crops (fruit trees, tobacco, etc.). Chloride ion has a certain inhibitory effect on nitrifying bacteria, and the nitrification leaching effect of nitrogen applied to soil is weaker than that of other nitrogen fertilizers. Therefore, ammonium chloride is a better nitrogen fertilizer in paddy field. The application of ammonium chloride should be combined with watering to try to leaching chloride into the subsoil so as to reduce its adverse effects on crops. Ammonium chloride is not suitable to be used as seed fertilizer. 4. Ammonium nitrate: the molecular formula is NH4NO3, containing 33-35% nitrogen. There are two kinds of ammonium nitrate: crystalline and granular, the former has strong hygroscopicity, while the latter has slightly worse hygroscopicity because of the anti-moisture agent on the surface. Ammonium nitrate is soluble in water and pH is neutral. Ammonium nitrate contains both ammonium nitrogen (NH4+-N) with less mobility in soil and nitrate nitrogen (NO3--N) with higher mobility, both of which can be well absorbed and utilized by crops. Therefore, ammonium nitrate is a good nitrogen fertilizer which does not leave any substance in the soil, and it is a physiological neutral fertilizer. Ammonium nitrate should be used as topdressing fertilizer for crops in dry fields, and it is more economical to apply it in small amounts. It is not suitable to be applied in paddy field or as base fertilizer or seed fertilizer.