Continuous cropping obstacles are the result of the combined effects of many factors within the crop and soil systems. Plants grow in the soil and have a close relationship with the soil. Continuous cropping obstacles are mainly caused by the unbalanced soil nutrients caused by the continuous planting of the same crops, the abnormality of soil microbial flora, and the accumulation of autotoxic substances secreted by plants or microorganisms in the soil, thus affecting crop growth.
In recent years, due to the increasing demand of potatoes, the economic benefits of planting potatoes are good. Therefore, in many areas, potatoes have become the main economic crops. However, potatoes are very sensitive to continuous cropping, and they are not suitable for continuous cropping, leading to continuous cropping phenomenon in global potato owners. Production areas are very common.
The reasons for continuous cropping obstacles are: 1. Soil nutrient imbalance. Continuous cropping will lead to the depletion of certain nutrient elements. If these nutrient elements are not supplemented in time, the healthy growth of the crops will be affected, which will lead to continuous cropping obstacles. However, the unnecessary elements of other crops will be accumulated excessively in the soil. The occurrence of secondary salinization will also cause continuous cropping obstacles. The content of available N, P, and K in the soil decreased after continuous cropping of potato; the total nitrogen, total P, and total salt content in the soil would decrease in the soil after four years of continuous cropping.
2. Soil microbial flora anomalies. The microorganisms in the soil can generally be divided into three categories: beneficial bacteria, neutral bacteria and harmful bacteria. Under normal rotation planting conditions, the quantity and proportion of the above three types of microorganisms in the soil are in a dynamic equilibrium. Although harmful microorganisms may exist, they will not become dominant populations in the soil and therefore will not affect the normal growth of the crops. After continuous cropping of crops, due to the presence of appropriate host and suitable growth environment, some pathogenic bacteria will rapidly multiply, eventually becoming the dominant group in the soil, thereby affecting crop growth, causing soil-borne diseases, and continuous cropping obstacles.
With the prolonged continuous cropping period, the number of dry rot pathogenic fungi, Fusarium spp., in potato root soil increased. After continuous cropping of potato, the number of cellulose-decomposing bacteria and nitrogen-fixing bacteria that were beneficial to the growth of potato in the soil decreased. After potato, the number of soil-borne pathogenic fungi, Fusarium oxysporum and Fusarium solani, increased, while the amount of antagonistic bacteria Chaetomium sp. decreased.
3. Accumulation of toxic substances. Plants mainly rely on roots to take up nutrients from the soil. Changes in soil chemistry and microecological environment have a great impact on normal plant growth. Among plant-secreted autotoxic substances, root exudates play a major role in plant growth. On the one hand, root exudates can directly affect the normal growth of crops by changing the chemical environment of the soil in the roots of crops; on the other hand, they can indirectly affect the healthy growth of plants by affecting the microbial flora in the root soil.
The prevention and control measures are as follows: 1. Change the planting system, make a reasonable rotation and intercropping. Through rotation, the number of pathogenic bacteria in the soil and the number of pests and diseases can be significantly reduced.
2. Concentrated burning of plant residues remaining in the field, and then returning plant ash to the field, which can effectively kill eggs, parasites, etc. remaining on the straw, and can effectively provide potassium fertilizer.
3. After the emergence of potatoes, 100 ml of avermectin 1000 times per plant is used to irrigate or avermectin is used for soil mixing, which can effectively control the occurrence of soil-borne diseases and insect pests.
4. Quantitative determination of the nutrient elements in the soil before sowing is conducted, and a reasonable fertilization system is established. Organic fertilizer is applied to improve soil structure.
5. Plant potato varieties resistant to continuous cropping (such as disease resistance, self-toxicity, salt tolerance, etc.).
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