With the increase in the amount of chemical fertilizers, the pollution of agricultural soils by chemical fertilizers is increasing day by day.

1. The loss of a large amount of chemical fertilizers makes the harmful substances in chemical fertilizers and excess ammonia, phosphorus and other nutrients pollute the soil, thereby deteriorating the physical and chemical properties of the soil. Long-term excessive application of chemical fertilizers will change the acidity and alkalinity of the soil, acidify or alkalize the soil, and directly affect the normal growth and development of crops; at the same time, excessive or improper fertilization will adversely affect soil microorganisms, resulting in a reduction of soil organic matter and fertility.
2. Nitrogen fertilizer accounts for about 80% of chemical fertilizers, and phosphate fertilizers account for about 20%. According to data, the utilization rate of nitrogen fertilizer applied to farmland is only 30% to 35%, and the utilization rate of phosphate fertilizer is only 10% to 20%. Therefore, the most serious environmental pollution is nitrogen fertilizer. Extensive use of nitrogen fertilizer makes the residue of nitrogen fertilizer in the soil accumulate, which is converted into nitrate and nitrite under the nitrification of the soil, which is absorbed by plants. The content of nitrate and nitrite in various crops, vegetables and pastures is greatly increased. Feeds with high nitrate content can cause livestock diseases or death; nitrates can also be reduced to nitrite in the human body, and then form carcinogens nitrosamines with secondary amines; nitrite concentrations reaching a certain level will trigger high iron Hemoglobin prion can make people have difficulty breathing. In severe cases, they can suffocate to death.
3. Excessive fertilizers can also enter surface water and groundwater through surface runoff and leaching, causing eutrophication of lakes, rivers, reservoirs and other water bodies.

Pesticides play an active role in agricultural production and occupy an important position in the integrated control of plant diseases and insect pests. However, in the process of pesticide use, most applicators cannot use pesticides rationally, resulting in reduced pesticide utilization, widespread pesticide abuse, frequent drug accidents, serious environmental pollution, and high agricultural product residues, which seriously affects the quality and efficiency of agricultural products. According to statistics, in the process of using pesticides to prevent pests and weeds, only 25% to 30% can be sprayed on the prevention and control targets. The proportion of pesticides sprayed on the target pests is less than 1%. Less than 0.03% of the total amount of pesticides used shows that the utilization rate of pesticides is low; the remaining 20%-30% will enter the atmosphere and water bodies, and 50%-60% will remain in the soil. In recent years, the pesticide industry has developed by leaps and bounds, and its varieties have continued to increase. Highly toxic and highly toxic pesticides have emerged one after another, the scope of use has continued to expand, and the amount of use has continued to increase. People are facing more and more serious pesticide pollution problems. How to reduce pesticide residues in agricultural products and the environment has become a research hotspot in countries all over the world.

1. The influence of pesticides on the soil The harm of pesticides to the soil is mainly reflected in its influence on the types, quantity and activity of microorganisms related to soil fertility, plant growth and plant diseases and insect pests. These effects are direct or indirect, inhibiting or promoting, temporary or permanent, reversible or irreversible, etc. For example, the extensive use of pesticides and herbicides will kill soil microorganisms or inhibit their activities. Soil fungicides and fumigants affect the balance of soil microbial systems. Pesticides affect soil microorganisms, which in turn affect the activity of soil enzymes and the conversion of nutrients, change the efficiency and speed of nutrient cycling in the agricultural ecosystem, and reduce the continuous productivity of the land. At the same time, pesticide residues in the soil will also cause heavy metal pollution, and once the soil is polluted by heavy metals, it will be difficult to recover.
2. The effect of pesticides on pests and their natural enemies. In nature, pests and natural enemies complement each other, and a large number of pesticides make the insects themselves high in pesticide content. After natural enemies prey on the pests, they accumulate a large amount of pesticides in their bodies under the action of bioconcentration. , And eventually died of poisoning. At the same time, the pesticides accumulated in the natural enemies can poison their offspring, causing various diseases and even death of the natural enemies of the offspring, resulting in a large reduction or even extinction of the natural enemies of the pests. In addition, the resistance of the pests themselves causes the pest population to increase rapidly, and the harm to the crops is greatly increased. Most of the insecticides currently in use have broad-spectrum insecticidal activity, which can kill non-target insects while killing pests. According to surveys, in the northeastern region of Japan, the use of chemical pesticides in apple orchards has rapidly reduced the number of pests. In just 10 years, the number of pests has dropped from 130 to 180 to a few. At the same time, more than 40 natural enemies of pests have become extinct, causing environmental and ecological imbalances.
3. Pesticide pollution to agricultural products After the application of chemical pesticides to prevent and control various pests and diseases, the plants themselves absorb a large amount of pesticides and penetrate into the plants, resulting in high residues of pesticides in the crops, which in turn pollutes agricultural products, especially pesticide residues in vegetable products Will directly endanger human health. Common pesticide residues mainly include organophosphorus and carbamate pesticides, such as omethoate, dimethoate, malathion, methamidophos, monocrotophos, fenthion, bekcarb, carbamicarb and carbamate Because of waiting. Among them, the annual consumption of highly toxic organophosphorus pesticides accounts for about 70%, and the milligram-level organophosphorus pesticides can cause deaths of humans and animals. When the pesticide residue in the human body reaches a certain amount and is not decomposed by the human body, various diseases will inevitably occur. In recent years, among various food poisonings, the proportion of food poisoning caused by pesticide residues has increased, and the poisoning deaths caused by pesticides accounted for about 20% of the total poisoning deaths. In addition, in the import and export of agricultural crops, due to excessive pesticide residues, my country’s agricultural crops have greatly reduced their international competitiveness, which directly caused economic losses.
4. Biomagnification of pesticides Under the natural laws of the food chain, organisms will continuously absorb toxic substances from environmental media or food and gradually accumulate and concentrate them in the body. In the entire ecosystem, pesticides are concentrated and amplified step by step through the transfer of bioconcentration and food chain. Human beings are at the top of the food chain and suffer the most. The unreasonable use of pesticides will eventually affect the development of organisms and induce embryonic deformities and mutations. In addition, pesticides remaining in the soil will also enter the atmosphere and water bodies through volatilization, diffusion, migration, and transformation. Pesticides in water and soil will not only exchange with pesticides in the atmosphere, that is, volatilization and sedimentation, but also can be absorbed into plants through plants.

The impact of agricultural film on the quality of agricultural products is much smaller than that of chemical fertilizers and pesticides. However, the main components of agricultural film include biphenol, phthalate, polyethylene, PCB, polychlorinated biphenyl and other substances. The molecular structure is very stable, it is difficult to carry out photolysis and thermal degradation under natural conditions, and it is not easy to be degraded by bacteria and enzymes. This will inevitably increase the number of plastic residues in the field. According to statistics, the annual residual amount of agricultural film in my country is as high as 350,000 tons, and the residual film rate is 42%, that is, nearly 50% of the agricultural film remains in the soil. As the agricultural film cannot be degraded in the soil, and the recycling of the mulch film has not been implemented well, the environmental pollution caused is also quite serious.

The undegraded agricultural film buried in the soil will have an adverse effect on the physical properties of the soil, which will directly affect the transfer of matter and energy in the soil, inhibit the growth of microorganisms, and change the characteristics of the soil. Residual agricultural film significantly reduces the bulk density of the cultivated layer soil, and the total porosity and non-capillary pores are significantly increased; the dispersion coefficient of the cultivated layer soil increases, and the structure coefficient decreases; experiments show that the percentage of the soil compacted carbon in the cultivated layer accounts for the total rot Significantly decreased throughout the growth period, which indicates that the mulching treatment consumes the organic carbon in the cultivated soil, which directly leads to the decline of soil fertility; the accumulation of residual plastic film also prevents the rising water flow to the root layer. The residual mulch makes the soil properties of the plough layer worse, which directly affects the growth of subsequent crops. In addition, after the plastic is decomposed in the natural environment, harmful substances will be generated, which will cause direct harm to the soil, and the inflow of harmful substances into water bodies can also cause immeasurable harm. Studies have shown that in wheat fields with continuous use of agricultural film for more than 2 years, the residual agricultural film per ha will reach 103.5 kg, and the yield of wheat will be reduced by 9%; for the wheat field continuously used for 5 years, the residual agricultural film will reach 375 kg per ha, and the yield of wheat will be reduced by 26%.