From slash-and-burn farming in rural areas to mechanized farming, in just a few decades, rural areas have undergone tremendous changes. Although the progress of agricultural technology has allowed us to enjoy the dividends of modern agriculture, it has inevitably caused serious damage to the soil. The following is a list of soil problems.
1. The tillage layer becomes shallower. Due to long-term mechanical tillage, rolling, and manual operations, most of the farmland soil has become shallower, with an effective living soil layer of about 15 cm. In addition to rainfall and irrigation, the "plow bottom layer" has moved up and thickened, forming a hard and deep barrier layer, which hinders the up and down operation of soil moisture, nutrients, and air, hinders the extension of crop roots, and the soil's water storage capacity is decreasing. Drought resistance continues to decline.
2. Reduced soil organic matter content. Farmland manure has not been applied for a long time, straw returning is rarely carried out, and green manure, the essence of traditional Chinese agriculture, has not been engaged in, and soil organic matter has not been replenished for a long time. Coupled with the excessive application of chemical nitrogen fertilizers, it has exacerbated the depletion of soil carbon. The soil organic matter content is seriously insufficient. The reduction of soil organic matter will cause a series of soil problems, such as soil acidification and secondary salinization, soil structure destruction, low soil fertility, and aggravation of soil-borne diseases.
3. The soil structure is damaged and compacted seriously. Due to the lack of organic fertilizer supplementation in the soil, as well as unreasonable tillage and unreasonable irrigation, the extensive application of chemical fertilizers has exacerbated the damage of the soil aggregate structure, resulting in more and more serious soil compaction, which directly affects the natural vitality and self-regulation ability of the soil.
4. Soil tends to acidify. Soil acidification is mainly due to the excessive use of chemical nitrogen fertilizers and physiological acidic fertilizers, resulting in an increase in acidic substances in the soil, which makes the soil acidified. Soil acidification will cause soil nutrient loss, soil harmful heavy metal activation, soil harmful microorganisms, especially parasitic fungi, increase, accelerate soil barrenness and soil-borne diseases.
5. Secondary salinization of soil. Due to the long-term excessive use of chemical fertilizers, salt in the soil continues to accumulate, especially nitrate accumulation. These salts accumulate to the surface, forming raw salinization at the surface of the soil, which can affect seed germination and seedling, hinder nutrient absorption, poor crop growth, and cause physiological drought, nutrient absorption disorders, soil structure damage, and even lead to salt damage, death, and permanent loss of agricultural use value.
6. The nutrient ratio of nitrogen, phosphorus and potassium in the soil is out of balance, and the medium and trace elements are seriously deficient. In daily management, the vast majority of farmers do not apply fertilizer in proportion, and often only apply a large amount of nitrogen and phosphorus fertilizers, resulting in a lack of potassium. Long-term failure to apply medium and trace element fertilizers results in the depletion of trace elements in the soil, the imbalance of the proportion of large amounts of nitrogen, phosphorus and potassium in the soil, and the imbalance of the nutrient ratio between large amounts of elements and medium and trace elements.
7. Soil pollution of farmland. Residual pollution from excessive use of chemical fertilizers, pesticides, and agricultural membranes, pollution from untreated organic fertilizers, and pollution from continuous cropping and pests and pathogens. These pollutants enter or remain in the soil for a long time, and once they exceed the soil's self-purification capacity, they will "overflow" and directly cause farmland soil pollution. After a large number of pollutants enter the soil, they will first destroy the ecological balance of the soil, cause a large number of beneficial organisms and beneficial microorganisms in the soil to die, reduce soil biological populations, deteriorate soil physical and chemical biological properties, decline in soil activity, and deterioration of soil function. Serious polluters will cause soil to lose capacity and lose agricultural use value.
8. "Soil disease" caused by continuous cropping of crops. Continuous planting of one or the same crop in the soil, due to the lack of micronutrients required by the crop due to continuous absorption, also allows some corresponding pathogens to multiply year after year, accumulating in large quantities in the soil, and the secretions of the roots of previous crops accumulate into toxic substances and form diseased soil.
9. Soil erosion. The main manifestations of soil erosion in cultivated land are water erosion, wind erosion and tillage erosion. Mainly due to over-reclamation by farmers, many hillsides are reclaimed for farmland. Especially for sloping land with a slope greater than 15 degrees, year after year of cultivation, soil erosion is extremely serious. Secondly, after reclamation, no protective tillage was implemented, such as slope ladder, horizontal ditch tillage, plant hedge protection, etc., but the land was dug and tilled at will, which not only caused tillage erosion, but also exacerbated wind erosion and water erosion. Long-term loss will inevitably lead to soil over-sand and reduced water and fertilizer retention capacity.
10. Facility agriculture soil comprehensive disorder disease. Facility cultivation is in a closed environment throughout the year or in a closed season. Due to high intensification, high multiple cropping index, high fertilizer input, high pesticide dosage, high intensity and high frequency human interference, excessive fertilization, the soil is in a state of high temperature and humidity for a long time, excessive irrigation, excessive tillage and trampling. Under such strong interference and huge pressure, soil health deteriorates sharply. Generally, after 2-3 years of planting, a series of soil diseases such as soil nutrient imbalance, soil acidification, soil secondary salinization, accumulation of soil harmful substances, soil microbial population diversity and functional degradation appear.
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