1. Nitrogen deficiency symptoms in plants:
Overall characteristics:
first, the lower old leaves began to yellow, and then gradually expanded to the upper new leaves.
In contrast to the symptoms of sulfur deficiency, Symptoms:
less monocotyledon tillers, less dicotyledon branches, slow growth;
late symptoms:
small ears, flat and thin grain.
2. ammonium nitrogen fertilizer
Mainly NH4HCO3, NH4Cl, (NH4)2SO4, NH3·H20, liquid NH3 and so on. Because it contains a common ammonia ion, it has the following common properties:
(1), Easy to dissolve and fast
(2), Ammonium ions are easy to adsorb by colloids, and not easy to lose in water
(3), in the early ventilation, nitration to nitrate ions
(4), in alkaline substances, easy to decompose and release ammonia gas
(I) Ammonium carbon (NH4HCO3)
This is the earliest production of nitrogen fertilizer in China, the production equipment is simple, and less investment.
1）. Properties: pure crystal is a white crystal, containing impurities is light gray,
containing 17% nitrogen, ammonia odor (volatile) strong hygroscopic, soluble
water, solution PH = 8.2- -8.4, alkaline.
2）. Application key points:
(1) Request deep-cover soil, and prohibit the withdrawal of the surface
(2) If the ground, it should be filled in time to reduce ammonia volatilization
(3) Ball making or grain making and deep application (compared with organic
moon bar and fine soil)
(4) Appropriate base fertilizer and topdressing should not be mixed
(5) A small amount of dry fine soil can be mixed when sprinkled in the paddy field
(II), Ammonium sulfate (standard nitrogen fertilizer)
properties: pure crystal is a white crystal, containing impurities for gray white or
light yellow, with a certain hygroscopic. soluble, acidic, nitrogen content of 20-21%
(generally 20% as standard nitrogen fertilizer N)
(1) suitable for all kinds of crops, can be used as a base, planting, topdressing, but
should be deep cover soil
(2) It is an acid chemical fertilizer, the most suitable for application in alkaline soil
(3) A large number of calcareous soil for long-term application, will cause soil
compaction (reasons)
(4) Long-term or large amounts of application in paddy fields will make the roots
of rice black and the leaves yellow
(III) Liquid ammonia It is a high concentration of liquid fertilizer made of ammonia plus high
pressure liquefaction, the nitrogen content of 82% (the highest), in storage and
transportation must use high-pressure resistant containers, such as tank trucks,
hydraulic (ammonia) tank. Liquid ammonia is difficult to use by artificial method
(such as a bucket, the basin can not be filled), so in the production of special liquid
ammonia fertilizer machine (similar to a large seeder), can complete the opening,
fertilization, soil cover, etc., after the soil immediately gasification into ammonia,
a small part of the loss, most of it is dissolved in soil water and form ammonia.
At present, the corps eight agricultural division part of the regiment field has
been applied.
3. nitrate fertilizer
It mainly includes ammonium nitrate, potassium nitrate, calcium nitrate, and so on.
Ammonium nitrate is widely used in production, and ammonium nitrate is taken as an example （1）The nature of ammonium nitrate
White crystal, containing impurities is white or light yellow, high nitrogen content of 33-35%, strong hygroscopic, caking after drying, in order to reduce its hygroscopic, often specially made into particles, the surface with a layer of hydrophobic substances (such as oil, paraffin, asphalt, etc.)
（2）Application method of ammonium nitrate
1) Suitable for mixed sand and soil, incredibly alkaline soil
2) It should be applied in the dry land, not in paddy fields (NO3—Easy to lose with water)
3) It is suitable for planting fertilizer or topdressing, and generally should not be used
in irrigated land, and not in humid areas
4) It is best suited for all crops, especially cash crops such as tobacco
5) Once the block can be smashed with a wooden stick, no iron crushing, otherwise, it will explode
6) It is appropriate to apply together with farm fertilizer and phosphorus and
potassium fertilizer, and should not be mixed with alkaline fertilizer
（3） Amide nitrogen fertilizer
There are mainly urea, lime nitrogen, etc. At present, the most used in China is urea,
molecular formula: CO (NH2)2
1. Properties of urea:
Pure products are white crystals or small particles, odorless and tasteless,
N contains about 4 6%, slightly hygroscopic, to reduce hygroscopicity,
more hydrophobic substances to make particle fertilizer (small ball),
easily soluble in water, neutral, easy to hydrolysis into ammonium carbonate:
CO(NH2)2+ 2H20→(NH4)2CO3
When heated at 6 0 degrees Celsius, bimolecular urea can be decomposed into a
single molecule, toxic, which is harmful to seed germination and seedling growth.
2. Application key points:
(1) Due to the hydrolysis before the use, it should be applied 4-7 days earlier
then the general nitrogen fertilizer,
(2) Easily divided into biurets due to heat, harmful to seeds. Therefore, it is not suitable
for seed fertilizer (seed mixing) if it is done, the amount should be controlled
such as wheat 2.5 kg/mu, the seeds should be kept dry, accompanied by sowing,
it is best not to mix the seeds, and it is not suitable for application at the seedling stage
(3) because of high nitrogen content is too large or withdrawal is not uniform,
easy to cause fertilizer damage.
(4) The most suitable for fertilization outside the root, the concentration of different
crops: cereal 1.5- -2.0%, cotton 0.5- -1.0%, vegetables 1.0%.
(5) The amount of base fertilizer is 1 5-3 0 kg/mu, and topdressing can be applied
in the early morning, and the depth of the acupoint application is 5 to 1 0cm.
4. Long-acting nitrogen fertilizer
To reduce the release rate and prolong the fertilizer effect. Even if too much
fertilization, it will not burn seedlings, which can meet the needs of nitrogen
throughout the whole growth period of crops.
It can be divided into two main categories:
(1) Synthesis of organic and long-acting nitrogen fertilizer
(2) coated fertilizer
1. Synthetic organic long-acting nitrogen fertilizer:
There is mainly urea formaldehyde, which is the organic matter produced by
the condensation of urea and formaldehyde. The nitrogen content of 38-40%
(slightly lower than urea) can be used as base fertilizer for sandy soil, because it is
expensive for ornamental plants and fruit trees.
2, coated with film fertilizer
It refers to the application of inert fertilizer on the surface of inert substances or
using semi-permeable, impermeable substances to wrap granular fertilizer to
make its slow release speed. Call it coated fertilizer.
At present, the inert substances used include sulfur, paraffin wax, resin and so
on. Production out is sulfur coat urea, coating urea, etc. Urea was widely used
from the 1970s to the early 1980s. In the 1990s, coating urea instead, the Guangzhou
nitrogen fertilizer plant produced coating liquid (patent product) mixed with urea,
which can greatly improve the utilization rate of urea.
5. Way to improve the utilization rate of nitrogen fertilizer
At present, the average utilization rate of nitrogen fertilizer in China is not high: 35-65% in paddy fields and 45-75% in dry land.
The main reasons for the low utilization rate of nitrogen fertilizer are:
(1) Ammonia (NH3) Of the volatile loss (in heaven)
(2) Nitrate root (N 03—) Ionic drip and infiltration (into the ground)
(3) Denitrification
To improve fertilizer efficiency, the following points should be made in the production:
(1) Reasonable distribution and selection of fertilizers
1. Different nitrogen fertilizer varieties are allocated according to different soil properties.
For example, dry land is mainly nitrogenous nitrogen, and paddy field is mainly ammonium nitrogen fertilizer.
2. Distribution of different nitrogen fertilizers according to different crops.
For example, rice is mainly ammonium nitrogen fertilizer, potato is mainly ammonia nitrogen fertilizer, tobacco is mainly nitrate nitrogen fertilizer, Nitrogen nitrogen fertilizer, and ammonium nitrogen fertilizer are also effective in corn and other cereal crops.
(2) Improve the fertilization technology
1. Nitrogen fertilizer should be applied to 1 0 to 1 5cm depth
2. Centralized application (fertilization is concentrated in the root system)
(1) Open the ditch application (fertilization a large, not as good as a line)
(2) Cave application on crops and vegetables
(3) Mix
(4) Touching the seedling roots and soaking the seedling roots
3. Fertilize soil
According to the different textures, that is, the soil quality is other to determine the number of fertilization: sand, loam, and clay in the amount of fertilization and the number of different. The most scientific method is to test the soil and fertilize the formula.
4, nitrogen fertilizer combined with other fertilizers application
With phosphorus fertilizer, and organic fertilizer.
(3) Application of N fertilizer synergist
Also known as nitrification inhibitors or nitrogen stabilizers. Can inhibit the growth activity of nitrous acid bacteria in the soil. In the ammonium state applied in the soil, the nitrogen fertilizer is not easy to nitrate, so as to reduce the loss of nitric acid ions and the loss of gaseous nitrogen.
At present, the synergies used in China are:
Chemical synthesis of polymer organic matter, such as trichloromethyl pyridine (CP), etc.
Application effect: rice field is better than irrigated land, and food crops are better than beans.
