Topic 2 Chemical Fertilizers

Topic 2

Chemical Fertilizers

Plant growth needs nutrients, and the nutrients that the soil can provide are limited, so it must be supplemented by fertilization, which is an important means to increase agricultural production. The fertilizers originally used by humans were natural organic fertilizers such as human and animal manure and plants. In the mid- 18th century, with people's understanding of the relationship between chemical elements and plant growth, chemical fertilizers (referred to as chemical fertilizers) made of chemical and physical methods containing nutrients needed for crop growth appeared. Later, with the growth of the world population, the human demand for agricultural products increased , and increasing the application of chemical fertilizers gradually became the most powerful measure to increase crop production .

1. Introduction to fertilizers

The nutrients necessary for crops include carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, etc. Among them, nitrogen, phosphorus, and potassium are required in large quantities, so nitrogen, phosphorus, and potassium fertilizers are the most important chemical fertilizers.

Some fertilizers contain two or three nutrients at the same time, such as ammonium phosphate (NH4H2PO4), ammonium dihydrogen phosphate [(NH4) 2HPO4] and potassium nitrate (KNO3), etc. Such fertilizers are compound fertilizers. The characteristic of this type of fertilizer is that it can evenly supply several nutrients to crops at the same time, fully exert the interaction between nutrient elements, and have high active ingredients. Fertilizers can also be specially processed and formulated according to actual needs. For example, ammonium phosphorus potassium is formulated and processed by adding potassium salt on the basis of ammonium phosphate.

Fertilizers play an important role in increasing crop yields. However, since chemical fertilizers often contain some heavy metal elements, toxic organic substances and radioactive substances, potential soil pollution will be formed after being applied to the soil; in addition, the accumulation, loss or change of certain components during the application of chemical fertilizers may cause soil acidification, water nitrogen and phosphorus content increase, nitrogen and sulfide gas ( N2O , NH3 , H2S, etc.) emissions, etc., causing soil degradation and pollution of water and atmospheric environment. Therefore, it is necessary to apply chemical fertilizers in a targeted, balanced and moderate manner according to soil and climate conditions, crop nutritional characteristics, chemical fertilizer properties and their changes in the soil, so as to improve application efficiency and reduce negative effects.

In addition to chemical fertilizers, chemical pesticides also play an important role in the high yield and harvest of agriculture. Pesticides are agents (except chemical fertilizers) that protect and improve agriculture, forestry, animal husbandry, and fishery production, including insecticides, fungicides, herbicides, rodenticides, and plant growth regulators. The amount of cereals that are reduced due to pests and diseases is 20% to 40% of the expected harvest every year in the world. For a considerable period of time in the future, the use of pesticides is still the most important means of crop protection. However, pesticides themselves are toxic substances, and improper use will bring pollution to the natural environment and harm to human health. Therefore, when applying pesticides, according to the occurrence and development of harmful organisms, it is necessary to prescribe the right medicine and use them in a timely manner, and to use pesticides in a reasonable manner according to the prescribed application amount, depth, and frequency, and to use different types of pesticides alternately, so as to give full play to the characteristics of different pesticides , to obtain the highest control effect with the least amount of pesticides; at the same time delay or prevent the emergence of drug resistance, thereby reducing the pollution of agricultural products and the environment by pesticides.

2. the simple identification of chemical fertilizers

Compare the appearance, odor and solubility in water of nitrogen fertilizers (hydrogen hydrogen carbonate, potassium chloride), phosphate fertilizers (phosphate rock powder, superphosphate) and potassium fertilizers (potassium sulfate, potassium chloride), and summarize their properties.

After studying this topic, you should know

1.Nitrogen, phosphorus and potash are important fertilizers.

2.Chemical fertilizers and pesticides play an important role in improving the yield of agricultural products, but they can also cause environmental problems. It is necessary to rationally apply chemical fertilizers and pesticides, increase their utilization rate, and pay attention to reducing pollution.

3.The method of preliminarily distinguishing common chemical fertilizers by using different physical and chemical properties