Basic Knowledge of Chemical Fertilizers in the Screening Industry
01 The Importance of Chemical Fertilizers
To increase grain production and at the same time increase profits, cooperatives mainly rely on the application of fertilizers, especially the application of chemical fertilizers. Some farmers think that applying chemical fertilizers is simple. They believe that for those fertilizers in the market, they can just buy them and give them a try. In fact, this is a kind of knowledge, and there are many problems to be solved. Moreover, its application is related to the technical level and soil conditions. Especially, under the situation of implementing protective tillage in many places nowadays, there are many problems in the application amount, application method and precautions of chemical fertilizers that need to be solved by us. Next, some basic knowledge of chemistry will be introduced, especially the properties of some commonly used fertilizers encountered in agricultural production.
We all know that the chemical fertilizers bought in the market include compound fertilizers, urea, potash fertilizers, and trace elements, etc. Normal crops need multi-element nutrients. In fact, normally there should be 17 elements, and among these 17 elements, nickel is one of them, and some people think it is essential. Just like people need to eat flour, rice and white flour, plants also need to "eat" certain substances. What do they "eat"? What we humans eat are mainly organic substances, while most of what crops and plants "eat" are inorganic substances in the form of ions. So, for example, urea can't be completely absorbed by plants directly. It needs to be converted into the form of ammonia first and then absorbed by plants, and the same principle applies to other elements such as phosphorus and potassium.
In fact, crops need 17 elements, mainly nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, zinc, copper, molybdenum, boron, manganese, nickel, chlorine, carbon, hydrogen, and oxygen. If a certain element is lacking during the growth process of crops, some symptoms and nutrient deficiency diseases will occur. For example, if there is a lack of nitrogen, corn will grow poorly. If there is a lack of phosphorus, the corn seedlings will be purple. If there is a lack of zinc, there will be stripy yellow substances on the new leaves during the seedling stage.
When corn lacks nitrogen, generally the lower leaves of corn will turn yellow. When it lacks phosphorus, the leaves will turn purple. When it lacks potassium, the leaves will be scorched. When tomatoes lack calcium, blossom end rot will occur. When corn lacks zinc, and when peach trees or apple trees lack iron or sulfur, some typical symptoms will appear. Overall, elements such as nitrogen, phosphorus, and potassium are not often lacking. Basically, trace elements such as zinc, sulfur, and iron are lacking in some places, especially in the saline-alkali soil in the western part of Jilin Province.
Fertilizers are the "food" of grains. Plants are the food of animals, and animals are the food of humans. For humans to live well, they need to eat a lot of meat, and we need to produce a large amount of grain. By using fertilizers to increase grain production, the entire food chain can have enough food. In the 1960s and 1970s, there was very little grain and almost no meat. This is because at that time, we lacked production methods for grain and the production of fertilizers.
China's chemical fertilizer enterprises account for 70% of the global total, the production volume accounts for 28% of the global total, and the output value accounts for 37% of the global total. If our country does not export phosphate fertilizers or other elements, many places in India, including Southeast Asia, Indonesia, and Malaysia, will face a fertilizer shortage. Therefore, the price increase of fertilizers this year, in addition to being affected by environmental protection in the year before last, is mainly due to the tight foreign market, where the foreign exchange price is higher than the domestic price, and also due to the impact of the epidemic, which has reduced the production volume in the United States and other countries. This situation has led to an increase in the price of agricultural products, and the prices of oil, natural gas, and even coal are also rising, because the production of chemical fertilizers mostly depends on coal, natural gas, and oil.
02 The Characteristics of Chemical Fertilizers
High nutrient concentration: Urea contains 46% nitrogen, while chicken manure contains only 2% nitrogen. So, applying one bag of urea is equivalent to applying several carts of chicken manure.
Quick effect: If nitrogen fertilizer is applied to corn on June 19, urea will show an effect within four or five days. However, if organic fertilizer is applied, it will take a long time to show an effect.
High solubility: Nitrogen fertilizers are basically completely soluble, some phosphate fertilizers are slightly soluble, and more than 90% of some fertilizers are soluble.
03 Introduction to Different Chemical Fertilizers
According to the classification of fertilizer types, they are divided into nitrogen fertilizers, phosphate fertilizers, potash fertilizers, compound fertilizers, and new fertilizers.
Nitrogen fertilizers: Urea, ammonium sulfate, and calcium nitrate (mostly used on fruit trees). We may not have seen some nitrogen fertilizers, but in fact, these substances are basically included in the fertilizers we use now. Compound fertilizers mostly contain ammonium sulfate, ammonium chloride, and urea.
a) Ammonium sulfate: In the entire Northeast market, among nitrogen fertilizers, ammonium sulfate ranks first. Ammonium sulfate is mainly used for rice seedling cultivation and as a greening fertilizer for rice. Ammonium chloride is relatively rare. However, some compound fertilizers sold in the market, especially those in the South, which have a high chlorine content, basically contain ammonium chloride because it is relatively cheap. Ammonium sulfate is an ammonium nitrogen fertilizer (containing 20%-21% nitrogen) and is physiologically acidic. There were some fertilizers in the form of ferrous sulfate (light green) before, which were the most commonly used fertilizers in the western part of Jilin Province. Because it is acidic, it may have a better effect when used on the soil with a relatively high pH in Liushu Liujia Guanzi, Shenyang Town, etc. The biggest feature of ammonium sulfate is that it can be used as a seed fertilizer without burning the seedlings. In addition, it can also be used as a top dressing and base fertilizer. And ammonium sulfate may be the earliest fertilizer in the international market.
b) Urea: In the market, farmers can see that there are large-particle and small-particle urea. The large-particle urea is relatively more expensive than the small-particle urea, with a price difference of 100-150 yuan per ton. The reason is that the large particles are mostly used for making blended fertilizers. When topdressing corn in June, small-particle urea is used because it has a quick effect and is also cheaper in price. Urea has the highest nitrogen content of 46%, which is a very good fertilizer. At the same time, it needs to be slowly converted in the soil. For example, in Liushu, if the fertilizer is applied around April 30, it will take 10-15 days for urea to be converted into the form of ammonium. But if topdressing is carried out in the middle and late June, it will basically all be converted into ammonium within 3-5 days, so the effect comes relatively quickly. Its conversion is related to the temperature. The more fertile the soil is, the faster the conversion is. So, for the protection of black soil and returning straw to the field, after returning straw to the field, the soil fertility increases, and the element conversion is relatively fast. Urea itself is a very good fertilizer, but its biggest feature is that it cannot be used as a seed fertilizer. It is best used as a top dressing and can also be used as a base fertilizer (deep application). Urea contains an impurity called biuret. If some people want to use urea for foliar fertilization, if the biuret exceeds the standard, it will burn the seedlings.
c) Ammonium nitrate types: Except for ammonium sulfate and urea, ammonium nitrate is not seen in the market. However, calcium ammonium nitrate and ammonium nitrate phosphate can be seen. Why are these fertilizers produced? Because calcium ammonium nitrate and ammonium nitrate phosphate have no explosion hazard. They are mainly used more on dryland crops in the South.
For corn, the best nitrogen fertilizer should be mainly nitro fertilizers. Because nitro fertilizers will not have a bad effect on seeds in the early stage, will not burn the seedlings, and can promote seed germination. So, it is recommended that everyone buy compound fertilizers containing nitro fertilizers.
Phosphate fertilizers:
a) The so-called phosphate fertilizers, for example, superphosphate, which people of our age used before, is called phosphate fertilizer. In fact, the production of phosphate fertilizers uses acids, alkalis, and the thermal method. The form of superphosphate is especially suitable for the chernozem in the western region. It has a particularly obvious effect when used on the soil with a high pH in the sandy soil. It has a better effect when combined with ammonium sulfate. Normal superphosphate can be used as a seed fertilizer, top dressing, and base fertilizer. Its biggest feature is that it is not easy to be mixed with urea because it will produce water when mixed with urea, and generally, it cannot be stored after mixing. But it also has an advantage that it can be used for foliar fertilization after filtration, and it is a very good fertilizer. At the same time, in addition to calcium and phosphorus, it also contains trace elements. So, we think that although the content of superphosphate in our country is relatively low, it can increase the content of trace elements in the soil.
b) Diammonium phosphate is applied more. The domestic diammonium phosphate currently used contains about 16%-18% nitrogen and has a pH of about 8, which is alkaline. Monammonium phosphate, which is less common in the market, has a pH of 5.5-6.5, contains less nitrogen, and has a higher phosphorus content. Its biggest advantage is that it is an acidic fertilizer. Most farmers in the western region use monammonium phosphate as a seed fertilizer instead of diammonium phosphate, which is the best way. It contains less nitrogen and more phosphorus, so it is most suitable for leguminous crops. It is also more suitable for use as a corn seed fertilizer because corn needs less nitrogen in the early growth stage. Especially in the Northeast region, from April to May, the temperature is low, and more phosphorus can promote root development. When the straw is covered, if you want the corn seedlings to grow fast in the early stage, you must use monammonium phosphate as a seed fertilizer to promote early development and raise the soil temperature that is reduced during the covering process, especially when using high-nitrogen fertilizer as a base fertilizer.
Potash fertilizers:
The most commonly used potash fertilizers are potassium chloride and potassium sulfate. Potassium chloride contains about 60% potassium and is physiologically acidic, containing potassium ions and chloride ions. Potassium ions are needed by crops, while chloride ions are only sometimes needed because it can produce acid. Potassium sulfate is mainly applied to vegetables. The overall price of potassium sulfate is higher than that of potassium chloride because the amount of pure potassium sulfate in nature is not much. In our country, only Lop Nur produces natural potassium sulfate. The potassium sulfate bought in the market now is basically converted from potassium chloride through sulfuric acid and other methods, which will increase the price of the product. So, potassium sulfate is generally used for cash crops, such as greenhouse vegetables, apples, and tobacco. It is generally used less for corn. In the greenhouse, potassium sulfate should be used instead of potassium chloride as much as possible because the harm caused by chloride ions in the greenhouse is more serious than that caused by sulfur ions. So, in summer, it is necessary to wash the greenhouse with rainwater, mainly to wash away the chloride ions, followed by sulfate ions, because both ions can cause plasmolysis. Potassium sulfate can be used as a base fertilizer, seed fertilizer, and top dressing, while potassium chloride can be used as a base fertilizer and top dressing, but not as a seed fertilizer. Plant ash is also called potash fertilizer, but its potassium content is very low.
04 Compound Fertilizers and Blended Fertilizers
The first one is a schematic diagram of a compound fertilizer. In a compound fertilizer, nitrogen, phosphorus, and potassium in each particle are evenly distributed. The second one is a blended fertilizer, and each particle contains only one element, and the form is different. Compound fertilizers are basically made through chemical reactions or physical processing, while blended fertilizers are just a blending process. According to the definitions of compound fertilizers and blended fertilizers, fertilizers containing two or more of nitrogen, phosphorus, and potassium are called compound fertilizers.
In the actual market, there are various types. In the entire corn production area of Jilin Province, most of them are high-nitrogen compound fertilizers (with a nitrogen content greater than 20%). High-nitrogen compound fertilizers have both advantages and disadvantages. At present, blended fertilizers in the market have a very beautiful color, but this is not their original color. They are dyed with dyes to make them more attractive to farmers. This thing looks very beautiful, but if children are not careful, they may mistake it for small sugar balls and eat it, which is actually very dangerous. Moreover, the dyes have an impact on the soil or the environment.
There is also a relatively popular compound fertilizer made by the tower granulation method in the market. It melts urea through the tower granulation method, fully mixes it with raw materials such as phosphorus and potassium, and then forms granules. Its biggest feature is that each granule is very beautiful and has a good smoothness. There is a problem with the control of biuret. The biuret content in urea itself is very low (toxic to crops), but if the tower granulation is not well controlled, biuret will be produced. The national standard for the biuret content is 1%, and if it exceeds 1.5%, it is very dangerous. Especially on sandy soil and sloping farmland, if it exceeds the standard, it is easy to burn the seedlings.
This is a case of toxicity caused after tower granulation. After some farmers applied the fertilizer made by tower granulation, the seedlings grew well at first, but then began to wither and eventually died. This is because the biuret in the soil has not decomposed and caused toxicity, and the biuret content has exceeded 3%, which is seriously beyond the standard.
It is recommended to use fertilizers such as 12:18:15, 20:12:13, 20:19:15 on the saline-alkali soil in the western region, aiming to increase the amount of phosphate fertilizer applied in the early stage and carry out topdressing in the later stage, because the soil in the western region is alkaline. The high-nitrogen compound fertilizers we use now are basically used on the black soil in the central region because the black soil has a strong fertilizer retention ability and will not lack fertilizer in the later stage. In the sloping farmland in the eastern mountainous area, many farmers still need to topdress with high-nitrogen fertilizers in the later stage. There is also a phenomenon in the central mountainous area: half-seeding. It is recommended that farmers use high-nitrogen fertilizers for half-seeding as little as possible, because it may cause the seedlings to be burned. Obviously, this is not a problem with the fertilizer, but a problem with the planting method. If there is full straw coverage or in low-lying land or in shady slope land, seed fertilizers (diammonium phosphate, monammonium phosphate) should be applied in combination. Generally, one or one and a half bags should be applied per hectare.
Next, slow/controlled-release fertilizers will be discussed:
It is recommended to use sulfur-coated fertilizers, especially in the corn production area in the Northeast, the effect of using sulfur-coated fertilizers is more obvious because the current soil is in a state of sulfur deficiency. But it must meet the national standards.
Seaweed acid, humic acid, and amino acid fertilizers are actually additives added to urea and compound fertilizers. It has a synergistic effect on the fertilizers themselves, will not do any harm, can increase the absorption of fertilizers by crops, and at the same time can reduce leaching and promote the stress resistance of crops.
05 Liquid Fertilizers
In the past seven or eight years, a liquid fertilizer that has a relatively fast production growth in China is the urea ammonium nitrate solution. In fact, this kind of fertilizer is widely used in the United States. It is actually a mixed solution containing ammonium nitrate and urea, and it has no explosiveness. So, it is applied to the soil in the form of a liquid. Through mechanical use, it can achieve a more obvious effect than urea and ammonium nitrate. It mainly uses a tank truck and a liquid fertilizer applicator to achieve the purpose of increasing the fertilizer efficiency. The reason for the good effect is that it makes full use of the combination with soil colloids. At the same time, it contains three forms of nitrogen, so the effect is more obvious.
The production of this kind of fertilizer in our country can reach about 1 million tons now, while in the United States, it can reach more than 10 million tons. The main reason is energy conservation. Because producing urea solution and ammonium nitrate solution saves more energy than producing urea granules and ammonium nitrate granules. At the same time, it saves plastic bags and prevents explosive pollution. It has a particularly good topdressing effect on corn. We carried out an effect experiment in the Liushu experimental area and found that applying this solution directly to the soil with a fertilizer applicator as topdressing or base fertilizer has a much better effect than urea, and the price is also relatively cheap.
In addition to urea ammonium nitrate in our country, many people are now researching low-cost monammonium phosphate, which can also be made into a liquid form. Polyammonium chloride can also be directly used as a liquid fertilizer. Using mechanical fertilization can achieve the purpose of increasing production.
06 Precautions for Fertilization
Select some fertilizers according to the properties of fertilizers. In particular, cooperatives should control the amount of fertilizer application according to the amount of straw returned and the time of returning straw to the field, because applying too much fertilizer will not only not increase production but may also reduce production.
Select suitable fertilizers according to the soil type. Cooperatives in the eastern mountainous area should select fertilizers with good controlled-release performance. High-nitrogen fertilizers should not be used on the saline-alkali soil in the western region. Sulfur-based compound fertilizers can be used, and then topdressing should be carried out.
Topdressing can achieve the purpose of increasing production. When we investigated with Director Wang, we found that if you want to achieve a yield of one ton per mu of land, it is impossible to achieve it without topdressing in the later stage.
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