1. Chemical fertilizer is the technological achievement of industrial revolution and the material support of modern agriculture.
Fertilizer originated in Europe and is the product of the industrial revolution. 1800, Britain took the lead in recovering ammonium sulfate as fertilizer from industrial coking, but it was not until 1908 that Germany invented the modern synthetic ammonia process to realize the sufficient supply of fertilizer. The application of chemical fertilizer has made Europe's living standard improve rapidly and become the world economic center. In view of the great contribution of chemical fertilizer to human civilization, freese Haber (19 18) and Karl Bosch (193 1), German inventors of synthetic ammonia technology, have successively won the Nobel Prize in chemistry.
(A) the characteristics and historical achievements of chemical fertilizers
Fertilizer comes from nature and has high supply efficiency. The main raw material of nitrogen fertilizer comes from the atmosphere, and other fertilizer raw materials are mainly minerals. The mechanism of nitrogen fertilizer production is similar to biological nitrogen fixation. Inert N2 in the atmosphere is transformed into active nitrogen (ammonium salt, nitrate) which can be used by crops through high temperature, high pressure and catalyst. A synthetic ammonia plant built on 10 hectare of land can produce 3000 tons per day, which can meet the needs of10 million mu of farmland to maintain the annual output of 8 million ~ 1000 kg in A Mu, which is about10 million times higher than the traditional biological nitrogen fixation efficiency. Chemical fertilizer makes farmland change from long-term fertilization-production to short-term continuous production, which greatly improves the output efficiency of farmland.
Fertilizer has high nutrient concentration and intensity, which reduces labor intensity. The nutrient content of chemical fertilizer is generally above 40%, which is more than 10 times that of traditional organic fertilizer. Urea contains 46% nitrogen, and only about 25 kg of urea is needed to meet the nitrogen supply of one mu of farmland 10 kg. A labor force can complete transportation and application by hand for half a day. However, in traditional agriculture, many people need several months to collect, compost, transport and apply organic fertilizers. Chemical fertilizer liberates farmers from heavy labor such as collecting fertilizer and composting, and greatly improves farmers' labor production efficiency.
Chemical fertilizer has fast fertilizer efficiency and is beneficial to the timely absorption of crops. The nutrients in chemical fertilizer are mainly inorganic and do not need to be decomposed by microorganisms. After being applied to soil, they will be quickly absorbed by crop roots. For example, chemical nitrogen fertilizer will be completely released in 3 ~ 15 days after it is applied to the soil, which can quickly meet the needs of crops in the vigorous growth period of plants. It can also be fertilized by irrigation or even foliar spraying, which greatly improves the nutrient absorption efficiency of crops.
Fertilizer itself is harmless. Fertilizer has high nutrient content and few impurities. For example, urea contains 46% nitrogen, which is a nutrient element needed by crops, and the rest is mainly CO2, which will be released into the atmosphere after being applied to soil, which is harmless. In addition, it also contains about 1% water and 1% biuret. Strictly controlled below 1.5%, it is harmless to crops, decomposes in soil and is used by crops and microorganisms. Other phosphate fertilizers, potash fertilizers and trace elements are all extracted from minerals, and their basic components are harmless.
(2) Fertilizer in China is hard-won.
At present, China is the largest producer and consumer of chemical fertilizers in the world. As a developing country, it is a great thing to meet its own fertilizer supply and export it abroad. The development of chemical fertilizer industry has provided a solid foundation for the sustained and rapid development of agriculture and national economy in China.
Ensuring the supply of chemical fertilizer is the basic strategy of the country. Since the founding of New China, chemical fertilizer has been the key guarantee of strategic resources, and even in difficult times, the growth of chemical fertilizer consumption has not stopped. The state has taken a series of measures to ensure the supply of chemical fertilizers, such as the policy of rewarding sales, the policy of centralized purchase and marketing without profit, production subsidies, application subsidies and so on. The subsidy amount in 20 13 years is as high as10 billion yuan. The special policy of chemical fertilizer has a long duration, a wide range and great strength, which is not available in other commodities.
Establish a fertilizer industry system at all costs. Fertilizer production is an industrial system highly dependent on resources, which is extremely difficult for developing countries with weak industrial base. Before 1980s, 40% of China's chemical investment, 50% of high-quality smokeless lump coal, 30% of imported natural gas and more than 60% of imported sulfur resources were used for fertilizer production. In order to improve the storage and transportation capacity of chemical fertilizers, the state has also built special railway lines, transmission lines, railways and wharf warehouses for large and medium-sized chemical fertilizer plants.
The road to technological innovation is very difficult. In the early days of the People's Republic of China, it was extremely difficult to import fertilizer production equipment and materials. China adheres to the policy of "self-reliance and self-sufficiency" and embarks on the arduous road of fertilizer research and development and production. After eight years' efforts, scientists such as Hou developed a fertilizer technology with China characteristics-"carbonation method" to produce ammonium bicarbonate, and built a modern nitrogen fertilizer industrial system with independent innovation. Phosphate fertilizer has been explored from superphosphate-calcium magnesium phosphate-nitrophosphate-ammonium phosphate-compound fertilizer for half a century. From 65438 to 0956, potash industry began prospecting in Qarhan Salt Lake in Qinghai, and it was not until the successful development of "reverse flotation and cold crystallization" process at the beginning of this century that large-scale production began.
(3) Chemical fertilizer is an important guarantee for eating well and being healthy.
The first Green Revolution in 1960s was an important milestone in the history of human development, which improved the supply of agricultural products through high-yield varieties, irrigation, mechanization and large-scale application of chemical fertilizers. According to FAO statistics, from 1960s to 1980s, developing countries increased the yield of food crops by 55% ~ 57% through fertilization, and chemical fertilizer is of greater significance to China.
Half of China's grain production comes from chemical fertilizers. Before the founding of New China, China has been using traditional agricultural production methods, that is, using crop straws, human and animal manure, green manure and other ways to improve soil fertility, and the grain output has been at a low level for a long time. From Qin and Han Dynasties to Qing Dynasty, the yield per mu of wheat and rice in China only increased from 106 kg and 80 kg to 195 kg and 29 1 kg. Since the founding of New China more than 70 years ago, the average yield per mu of wheat in China has reached 700-800 kg, and the high-yield areas have reached 1.500 kg. Among them, the application of chemical fertilizer plays a key role. Scientists have proved that the yield difference between crops without chemical fertilizer and crops with chemical fertilizer is 55% ~ 65%.
Chemical fertilizer has significantly improved the nutritional level of people in China. In recent years, the per capita supply of vegetables and fruits in China has continued to increase, enriching recipes and improving the nutritional level of residents. The per capita animal protein supply increased from 196 1.4 kg in 0 year to 15.5 kg in 20 14 year. The increase of fruit and vegetable output is mainly through modern production methods (greenhouse, irrigation, chemical fertilizer and pesticide). The growth of meat products and dairy products comes from the increase of feed supply, and feed production also depends on the application of chemical fertilizers. Chemical fertilizer greatly enriches the nutrient supply in agricultural production system, and provides a basis for producing more protein, energy and minerals needed by human beings.
Chemical fertilizer has improved soil fertility. Cultivated land quality is the basic guarantee of food security. In traditional agriculture, the nutrient content of cultivated land is mainly determined by pedogenic minerals, and most soils lack nutrients to varying degrees. For example, the content of soil available phosphorus in China is relatively low. According to the data of the second soil survey in 1980s, the average content was only 7.4mg/kg (for example, the optimum content of corn should not be less than 8mg/kg). Through the application of phosphate fertilizer, the content of available phosphorus in soil in China has increased to 23mg/kg in recent 30 years. Fertilization can also increase crop biomass, improve surface coverage and reduce soil erosion. Soil itself is also a carbon sink, which can store greenhouse gases produced by human activities and reduce the negative impact of industrialization. In addition, the application of chemical fertilizer can increase the yield of crops and provide a broad land space for urban construction, transportation and industrial and commercial development.
Second, scientific understanding of several problems in the utilization of chemical fertilizers
At present, the application of chemical fertilizer has brought some problems, but people have many misunderstandings about it, resulting in some negative effects being over-amplified. In fact, it is easy for everyone to understand that fertilizer is compared to food. A series of health problems such as hypertension, hyperlipidemia and hyperglycemia caused by unreasonable diet and overnutrition are food intake problems, not food itself. Like diet, the wrong ways such as excessive application of chemical fertilizers, unreasonable nutrition collocation and extensive application methods will also have negative effects, but they need scientific analysis, correct understanding and rational treatment.
(A) the relationship between chemical fertilizer application and non-point source pollution.
At present, water pollution has been more prominent, but there are three main sources of water pollutants: agricultural non-point source discharge, sewage discharge from industrial enterprises and urban and rural residents, and atmospheric dry and wet deposition related to fossil energy discharge. According to the Bulletin on Environmental Status of China in 20 14, the total amount of ammonia nitrogen discharged from wastewater in China is 2.385 million tons, including domestic source 138 1000 tons, agricultural source 755,000 tons, industrial source 232,000 tons and centralized source 17000 tons. It can be seen that agricultural sources are lower than domestic sources. Agricultural non-point source pollution includes fertilizer loss and nitrogen and phosphorus nutrient loss caused by livestock and poultry breeding and aquaculture. According to the research, the contribution of fertilizer nutrient loss to agricultural nitrogen and phosphorus emissions is 1 1.2% and 25.7% respectively, which is generally low. In fact, most of the phosphorus and potassium elements absorbed by crops in this season will remain in the soil and be used by crops in the next season.
(2) The relationship between chemical fertilizer application and air pollution.
Air pollution, especially smog, has had a great impact on our lives. Generally speaking, nitrogen fertilizers used in agricultural production, such as urea, ammonium bicarbonate, diammonium phosphate, etc., enter the soil and are not absorbed and utilized by crops, and some nitrogen will be discharged into the atmosphere in the form of ammonia and nitrogen oxides, causing air pollution. These losses are very small if the soil is deeply covered, applied by stages and reasonable products are selected. The research shows that at present, the contribution of nitrogen fertilizer to the total emission of nitrogen oxides in China is about 5%. With the change of fertilization methods, this ratio will gradually decrease.
(3) The relationship between chemical fertilizer application and soil quality.
In recent years, soil health problems in China have aroused widespread concern. Farmers intuitively feel soil compaction pollution, which simply boils down to the role of chemical fertilizers. In fact, soil hardening is not the function of chemical fertilizer. Soil hardening is mainly caused by flooding irrigation, flooding irrigation and unreasonable farming. Rational use of chemical fertilizers, especially organic fertilizers, can improve soil structure. In addition, chemical fertilizer has little effect on soil heavy metal pollution. Only ammonium phosphate will bring in a certain amount of heavy metals in chemical fertilizer, and the cadmium content in phosphate rock in China is very low. According to the current fertilization amount (50 kg/mu, calculated by the average cadmium content 10 mg/kg), the cadmium brought in every year is only 0.5 g/mu, while the cadmium brought in by industrial and mining and sewage irrigation is much higher than that of chemical fertilizer.
(d) The relationship between the application of chemical fertilizers and the quality of agricultural products.
The appearance, nutrition, inclusion composition and storage characteristics of agricultural products are directly related to the application of chemical fertilizers. People often say that "the melon is not fragrant, the fruit is not sweet, and chemical fertilizer is used", which is the result of unreasonable application of chemical fertilizer. Some fruit farmers blindly pursue large fruit and super-high yield, invest a lot of nitrogen fertilizer and ignore the cooperation of other elements, resulting in large fruit and more water, but the soluble solids and sugar content can not keep up, which reduces the flavor. In fact, the quality of crops is related to the proportion of nutrient absorption. The nutrient structure and application method of chemical fertilizer are reasonable, melons and fruits grow healthily, and the fruits are more fragrant and sweeter.
Third, promoting weight loss and increasing efficiency is a key measure to adjust agricultural structure and mode and realize green development.
General Secretary Xi Jinping pointed out, "We should unswervingly accelerate the transformation of agricultural development mode, shift to the intensive development of paying equal attention to quantity, quality and benefit, improving competitiveness, agricultural scientific and technological innovation and sustainable development as soon as possible, and take the road of modern agricultural development with high output efficiency, product safety, resource conservation and environmental friendliness". At present, China's agricultural production has been squeezed by the price ceiling and the cost floor. Only by changing the mode of production and reducing the already high cost of agricultural materials can we improve agricultural quality and increase efficiency, save costs and increase efficiency.
In agricultural production, chemical fertilizers and pesticides are the main material inputs. Generally speaking, wheat, corn and rice account for 45% of the material input. Horticultural crops are even higher, and the input of chemical fertilizers and pesticides in apple production accounts for 2/3 of the total material cost. The main reason why the price of agricultural products can't go up is that the quality is not too hard, and chemical fertilizer is the decisive factor of quality. The problem of resources and environment has gradually become a rigid constraint factor affecting agricultural production. Environmental deterioration will not only directly increase the cost of agricultural production, but also indirectly increase the cost of agricultural production. Therefore, the importance of chemical fertilizer in transforming agricultural production mode is self-evident. Based on the national conditions, in accordance with the requirements of "increasing production and fertilization, economic fertilization and environmental protection fertilization", we will carry out the action of zero growth in fertilizer use, implement the four-word policy of "precision, adjustment, reform and substitution", and gradually correct the face of excessive and unreasonable fertilization.
Precision means promoting precision fertilization.
According to the soil conditions, crop yield potential and comprehensive nutrient management requirements in different regions, the fertilization limit standards for each region and crop unit area are reasonably formulated. Hundreds of thousands of soil testing and formula fertilization experiments have proved that precision fertilization can achieve the effect of reducing the weight of grain crops by 5 kg per mu, increasing the yield by 5-8% and increasing the income by 100 yuan, while cash crops such as fruits, vegetables and tea can reduce the weight by 20-90 kg per mu, increasing the yield by 10-20% and increasing the income by more than 2,000 yuan. However, due to the diversity of soil types and the complex planting system in China, there are more than 700 million cultivated land. It is a long-term work to realize accurate fertilization on each land, which requires the comprehensive guarantee of technology, policy and system.
Adjustment is to adjust the use structure of chemical fertilizers.
Farmers in China are too scattered, so in the past, general chemical fertilizer products have been the main products, which can meet the basic production requirements, but they are not optimal. First of all, it is necessary to optimize the ratio of nitrogen, phosphorus and potassium, enhance the coordination and coordination of large elements and medium and trace elements, and make soil crops more nutritious. Secondly, according to the different soil conditions and crop needs in China, we should develop suitable high-efficiency fertilizer products and ensure that these products can be used in the field. This requires the chemical fertilizer industry to meet the needs of agriculture to upgrade products, the chemical fertilizer marketing system to truly serve users, and to carry out in-depth innovation and localization technology in the agricultural field.
Change means improving fertilization methods.
At present, due to the shortage of labor and agricultural machinery, unreasonable fertilization phenomena such as surface application, spreading application and "instant success" are more common. It is necessary to speed up the research and development of suitable fertilization equipment and promote the transformation of fertilization methods. For example, the volatilization of nutrients in the top layer of nitrogen fertilizer will exceed 20%, while the application in the deep layer of soil can be reduced to less than 5%. The application of water to vegetables in protected areas and some field fertilizers can be gradually changed to the integration of water and fertilizer and foliar spraying. The change of fertilization method needs the close cooperation of fertilizer products, agricultural machinery, agronomy and facilities, which is a systematic project and needs long-term strengthening and promotion.
Substitution means that organic fertilizer partially replaces chemical fertilizer.
The aquaculture industry in China is very developed, and the nutrients contained in organic fertilizer are almost the same as those provided by chemical fertilizer. However, the nutrient return rate of organic fertilizer is only about 40%, which not only fails to exert fertilizer efficiency, but also becomes a pollution source. At present, most grain fields and orchards do not use organic fertilizer, which not only affects the yield, but also restricts the improvement of soil productivity in the long run. Through rational utilization of organic nutrient resources, especially replacing part of chemical fertilizers with organic fertilizers on fruits, protected vegetables and tea, the combination of organic and inorganic materials can be promoted, the basic fertility of cultivated land can be improved, and the yield and efficiency can be increased.
In a word, fully understanding the role of chemical fertilizers and actively and reasonably changing fertilization methods are important events to ensure China's food supply and sustainable development. In order to change the wrong ideas such as "more fertilization and more yield increase" and the wrong practices such as "no need to ask people for water and fertilizer", we should not go to extremes and demonize chemical fertilizers, thus denying chemical fertilizers across the board. Scientific and reasonable understanding of chemical fertilizers, correct and reasonable application of chemical fertilizers and innovative chemical fertilizer products based on modern agricultural development are the correct direction.