The importance of fertilizer

Fertilizer, as the food of plant, is an efficient nutrient to all cash and open-field crops. Since the production of ammonium sulfate in Europe in 1800, after more than 200 years of development, fertilizers have formed a complete production, supply, sales, and use system, which can provide essential mineral elements such as nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, manganese, copper, zinc, boron, molybdenum, chlorine, and beneficial elements such as silicon for agricultural products such as grain, cotton, oil, fruits, and vegetables. Over the past 200 years of using chemical fertilizers, while the population has continuously doubled, the level of nutrition has greatly improved, and human civilization has shown exponential growth, completely breaking through the bottleneck of traditional agriculture relying on natural recovery of soil fertility.

1、 Fertilizer is a technological achievement of the Industrial Revolution and a material support for modern agriculture

Fertilizer originated in Europe and is a product of the Industrial Revolution. In 1800, Britain was the first to recover ammonium sulfate from industrial coking as fertilizer, but it was not until Germany invented the modern synthetic ammonia process in 1908 that sufficient supply of fertilizer was achieved. The application of fertilizers has rapidly improved the living standards in Europe and made it the center of the world economy. Given the significant contribution of fertilizers to human civilization, Fritz Haber (1918) and Carl Bosch (1931) from Germany, inventors of synthetic ammonia technology, were awarded the Nobel Prize in Chemistry.

（1） Characteristics and historical achievements of fertilizers

Fertilizer comes from nature and has high supply efficiency. The main raw material for nitrogen fertilizer comes from the atmosphere, while other fertilizer raw materials are mainly minerals. The production of nitrogen fertilizer is similar to the mechanism of biological nitrogen fixation, which converts inert N2 in the atmosphere into active nitrogen (ammonium salts, nitrates) that crops can utilize through high temperature, high pressure, and catalysts. A synthetic ammonia plant built on 10 hectares of land can produce 3000 tons of nitrogen per day, which can meet the annual production of 800-1000 kilograms per mu of farmland for millions of acres. The efficiency of nitrogen fixation is about one million times higher than that of traditional biological methods. Fertilizer has transformed farmland from a long cycle of fertilization production to a short cycle of continuous production, greatly improving the efficiency of farmland output.

Fertilizer has a high nutrient concentration and strong energy, which reduces labor intensity. The nutrient content in fertilizers generally exceeds 40%, which is more than 10 times that of traditional organic fertilizers. Urea contains 46% nitrogen, and only about 25 kilograms of urea are needed to meet the nitrogen supply of 10 kilograms per acre of farmland. One laborer can transport and apply it in half a day by hand. However, traditional agriculture requires many people to spend several months collecting, composting, transporting, and applying organic fertilizers. Fertilizer has liberated farmers from the heavy labor of collecting and composting fertilizers, greatly improving their labor productivity.

Fertilizer has fast efficiency and is beneficial for crops to absorb in a timely manner. The nutrients in fertilizers are mainly inorganic and do not require microbial transformation and decomposition. After being applied to the soil, they will be quickly absorbed by crop roots. For example, chemical nitrogen fertilizer is usually fully released within 3-15 days after being applied to the soil, which can quickly meet the needs of crops during the vigorous growth stage of plants. Fertilizer can also be applied through irrigation or even foliar spraying, greatly improving the nutrient absorption efficiency of crops.

Fertilizer itself is harmless. Fertilizer has high nutrient content and low impurities. For example, urea contains 46% nitrogen, which is a nutrient required by crops, while the rest is mainly CO2. After being applied to the soil, it will be released back into the atmosphere and is harmless. In addition, it contains about 1% water and about 1% biuret. Biuret is strictly controlled below 1.5% and is harmless to crops. It will also decompose in the soil and be utilized by crops and microorganisms. Other phosphate fertilizers, potassium fertilizers, and trace elements are extracted from minerals, and their basic components are also harmless.

（2） Chinese fertilizers are hard won

Currently, China is the world's largest producer and consumer of fertilizers. As a developing country, it is remarkable to be able to meet its own fertilizer supply while also exporting to foreign countries. The growth of the fertilizer industry has provided a solid foundation for the sustained and rapid development of China's agriculture and national economy.

Ensuring the supply of fertilizers is a fundamental national strategy. After the establishment of the People's Republic of China, fertilizer became a key strategic resource guarantee, and even in difficult times, the growth of fertilizer usage never stopped. The country has taken a series of measures to ensure the supply of fertilizers, such as incentive sales policies, non-profit unified purchase and sales policies, production subsidies, and application subsidies. In 2013, the subsidy amount exceeded 100 billion yuan. The duration, scope, and intensity of the special policy for fertilizers are unparalleled by any other commodity.

Establishing a fertilizer industry system at any cost. Fertilizer production is an industrial system highly dependent on resources, which is extremely difficult for developing countries with weak industrial foundations. Before the 1980s, 40% of China's chemical industry investment, 50% of high-quality smokeless lump coal, 30% of imported natural gas, and over 60% of imported sulfur resources were used for fertilizer production. In order to improve the storage and transportation capacity of fertilizers, the country has also built dedicated railway lines, transmission lines, railways, and dock warehouses for large and medium-sized fertilizer plants.

The road to technological innovation is extremely difficult. In the early days of the founding of the People's Republic of China, it was extremely difficult to import fertilizer production equipment and materials. Adhering to the principle of "self-reliance and self-sufficiency", China has embarked on a difficult path of fertilizer research and production. Scientists such as Hou Debang have been working hard for 8 years since the 1950s to develop a fertilizer technology with Chinese characteristics - the "joint alkali method" for producing ammonium bicarbonate, and have established a modern nitrogen fertilizer industry system with independent innovation. Phosphate fertilizer has been explored for half a century from superphosphate calcium magnesium phosphate fertilizer nitrophosphate ammonium phosphate compound fertilizer. The potassium fertilizer industry began searching for minerals in the Qarhan Salt Lake in Qinghai in 1956 and only began large-scale production after the successful development of the "reverse flotation cold crystallization" process at the beginning of this century.

（3） Fertilizer is an important guarantee for having enough to eat, eating well, and eating healthily

The first Green Revolution in the 1960s was an important milestone in human development history, which increased the supply of agricultural products through high-yield varieties, irrigation, mechanization, and extensive use of fertilizers. According to the Food and Agriculture Organization of the United Nations (FAO), from the 1960s to the 1980s, developing countries increased crop yields by 55% to 57% through fertilization, and chemical fertilizers were even more significant for China.

Half of China's grain production comes from fertilizers. Before the establishment of the People's Republic of China, the country had been using traditional agricultural production methods, such as using crop straw, human and animal manure, green manure, etc. to fertilize the soil, resulting in a long-term low level of grain production. During the more than 2000 years from the Qin and Han dynasties to the Qing dynasty, the yield of wheat and rice per mu in China increased from only 106 jin and 80 jin to 195 jin and 291 jin, respectively. In the more than 70 years since the founding of the People's Republic of China, the average yield of wheat in China has reached 700-800 catties, with high-yield areas reaching 1500 catties. Among them, the application of fertilizers played a key role. Scientists have shown that there is a 55% to 65% difference in crop yield between crops without and with chemical fertilizers.

Fertilizer has significantly improved the nutrition level of countrymen people. In recent years, the per capita supply of vegetables and fruits in China has continued to grow. While enriching the diet, it has also improved the nutritional level of residents. The per capita supply of animal protein increased from 1.4 kilograms in 1961 to 15.5 kilograms in 2014. The increase in fruit and vegetable production is mainly achieved through modern production methods such as greenhouses, irrigation, fertilizers, and pesticides. The growth of meat and dairy products comes from the increase in feed supply, and feed production also relies on the application of fertilizers. Fertilizer greatly enriches the nutrient supply in the agricultural production system, providing a foundation for producing more protein, energy, and minerals needed by humans.

Fertilizer improves soil fertility. The quality of arable land is the fundamental guarantee for food security. In traditional agriculture, the nutrient content of cultivated land is mainly determined by soil minerals, and the vast majority of soils exhibit varying degrees of nutrient deficiency. For example, the available phosphorus content in Chinese soil is relatively low. According to the data from the second soil survey conducted in the 1980s, the average content is only 7.4mg/kg (for example, the most suitable content for corn should not be less than 8mg/kg). By applying phosphorus fertilizer, the available phosphorus content in Chinese soil has increased to 23mg/kg in the past 30 years. Fertilizer application can also increase crop biomass, improve surface coverage, and reduce soil erosion. Soil itself is also a carbon sink that can store greenhouse gases generated by human activities and mitigate the negative impacts of industrialization. In addition, increasing crop yields through the application of fertilizers provides vast land space for urban construction, transportation, industrial and commercial development.

2、 Several Issues in Scientific Understanding of Fertilizer Utilization

Nowadays, the application of fertilizers has brought some problems, but there are many misunderstandings about it, which has led to some negative impacts being overly amplified. In fact, comparing fertilizer to food is easy for everyone to understand. The series of health problems caused by unreasonable diet and overnutrition, such as hypertension, hyperlipidemia, and hyperglycemia, are a problem of food intake, not the food itself. Like diet, excessive use of fertilizers, unreasonable nutrient combinations, and extensive application methods can also have negative effects, but scientific analysis, correct understanding, and rational treatment are needed.

（1） The relationship between fertilizer application and non-point source pollution. At present, water pollution is quite prominent, but there are three major sources of water pollutants: agricultural non-point source emissions, industrial enterprises and rural and urban residents' sewage emissions, and atmospheric dry and wet deposition related to fossil energy emissions. According to the 2014 China Environmental Status Bulletin, the total discharge of ammonia nitrogen in wastewater in China was 2.385 million tons, including 1.381 million tons from domestic sources, 755000 tons from agricultural sources, 232000 tons from industrial sources, and 17000 tons from centralized sources. It can be seen that agricultural sources have lower emissions than domestic sources. Agricultural non-point source pollution includes fertilizer loss, nitrogen and phosphorus nutrient loss caused by livestock and poultry farming, and aquaculture. According to research, the contribution of nutrient loss from fertilizers to agricultural source nitrogen and phosphorus emissions is 11.2% and 25.7%, respectively, which is generally low. In fact, most of the phosphorus and potassium elements absorbed by current season crops in fertilizers will still remain in the soil and be utilized by next season's crops.

（2） The relationship between fertilizer application and air pollution. Air pollution, especially haze, has had a significant impact on our lives. Generally speaking, if ammonium nitrogen fertilizers such as urea, ammonium bicarbonate, and diammonium phosphate applied in agricultural production are not absorbed and utilized by crops after entering the soil, some of the nitrogen will be emitted into the atmosphere in the form of active nitrogen such as ammonia and nitrogen oxides, causing air pollution. If deep soil covering, phased application, and reasonable product selection are adopted, these losses are very small. Research has shown that nitrogen fertilizer currently contributes about 5% to the total nitrogen oxide emissions in China. With the change of fertilization methods, this proportion will gradually decrease.

（3） The relationship between fertilizer application and soil quality. In recent years, soil health issues in China have attracted widespread attention. Farmers intuitively feel that the soil is compacted and polluted, which can be simply attributed to the role of fertilizers. Actually, soil compaction is not the effect of chemical fertilizers. Soil compaction is mainly caused by flooding, inundation, and unreasonable cultivation. Reasonable use of chemical fertilizers, especially when combined with organic fertilizers, can improve soil structure. In addition, the impact of fertilizers on soil heavy metal pollution is minimal. Only ammonium phosphate in fertilizers can bring in a certain amount of heavy metals. The cadmium content in phosphate ore in China is very low. According to the current fertilization rate (50 kg/mu, calculated based on an average cadmium content of 10 mg/kg), the amount of cadmium brought in each year is only 0.5 g/mu, while the amount of cadmium brought in by industrial and mining mining mining and sewage irrigation is much higher than that of fertilizers.

（4） The relationship between fertilizer application and agricultural product quality. The appearance, nutrition, content composition, and storage characteristics of agricultural products are directly related to the application of fertilizers. The common people often say that "using chemical fertilizers makes melons lose their fragrance and fruits lose their sweetness", which is the result of unreasonable application of chemical fertilizers. Some fruit farmers blindly pursue large fruits and super high yields, investing a large amount of nitrogen fertilizer and neglecting the coordination of other elements, resulting in large fruits with a lot of water, while soluble solids and sugar content cannot keep up, which reduces the flavor. In fact, crop quality is related to the proportion of nutrient absorption. Reasonable fertilizer nutrient structure and application methods result in healthier growing fruits that are more fragrant and sweeter.

3、 Promoting fertilizer reduction and efficiency improvement is a key measure for agricultural structural adjustment, transformation, and achieving green development

General Secretary Xi Jinping pointed out that we must firmly accelerate the transformation of the agricultural development mode, and quickly shift to a modern agricultural development path that emphasizes both quantity, quality, and efficiency, focuses on improving competitiveness, agricultural technology innovation, and sustainable intensive development. We must take the path of efficient output, product safety, resource conservation, and environmental friendliness. At present, China's agricultural production is facing a dual pressure of price "ceiling" and cost "floor". We can only transform our production methods and reduce the already excessive cost of agricultural materials in order to achieve agricultural quality and efficiency improvement, cost savings and efficiency enhancement.

In agricultural production, fertilizers and pesticides are the main material inputs. Generally speaking, the three major grains of wheat, corn, and rice account for 45% of material inputs in terms of fertilizers and pesticides. Horticultural crops are even higher, with fertilizer and pesticide inputs accounting for two-thirds of the total material cost in apple production. The main reason why agricultural product prices cannot rise is that the quality is not strong enough, and fertilizers are the decisive factor in quality. Resource and environmental issues have gradually become rigid constraints on agricultural production. The deterioration of the environment not only directly increases agricultural production costs, but also indirectly increases the cost of governance. Therefore, the importance of fertilizers in transforming agricultural production methods is self-evident. Based on the national conditions and in accordance with the requirements of "increasing production and fertilization, economic fertilization, and environmental protection fertilization", we will carry out the zero growth action of fertilizer use, implement the four character policy of "refinement, adjustment, improvement, and replacement", and gradually correct the situation of excessive and unreasonable fertilization.

Precision means promoting precise fertilization. Reasonably formulate fertilization limit standards for each region and crop unit area based on soil conditions, crop yield potential, and nutrient comprehensive management requirements. Hundreds of thousands of experiments have proven that precise fertilization can achieve a weight loss of 5 kilograms, an increase in yield of 5-8%, and an increase in income of 100 yuan per mu of grain crops, while economic crops such as fruits, vegetables, and tea can lose 20-90 kilograms, increase yield by 10-20%, and increase income by over 2000 yuan. However, due to the diverse soil types and complex planting systems in China, with over 700 million farmland plots, achieving precise fertilization for each plot is a long-term task that requires comprehensive technical, policy, and institutional support.

Adjustment refers to adjusting the structure of fertilizer use. Chinese farmers are too scattered, so in the past, they have mainly relied on generic fertilizer products, which can meet basic production requirements but are not optimal. Firstly, it is necessary to optimize the ratio of nitrogen, phosphorus, and potassium, enhance the synergistic effect of large and trace elements, and make soil crop nutrition more efficient. Secondly, it is necessary to develop suitable and efficient fertilizer products based on different soil conditions and crop needs in China, and ensure that these products can be used in the field. This requires the fertilizer industry to upgrade its products to meet the needs of agriculture, the fertilizer marketing system to provide genuine services to users, and the agricultural sector to deeply innovate and localize technology.

Change means improving the fertilization method. At present, due to labor shortage and insufficient agricultural machinery, unreasonable fertilization phenomena such as surface application, scattered application, and "one bombardment" of fertilizers are quite common. We need to accelerate the development and promotion of suitable fertilization equipment, and promote the transformation of fertilization methods.