Continuous Cropping Obstacle
What are the manifestations of vegetable continuous cropping obstacles? It mainly manifested in the decrease of yield, serious pests and diseases, and the decline of quality. There are many reasons for the obstacles of continuous cropping of vegetables. Next, I will introduce the reasons for that and the prevention and control measures. I hope it can be helpful to everyone. help.
1. Definition of Continuous Cropping Obstacles
It refers to the phenomena of long-term stunting, reduced yield, poor quality, and severe pests and diseases after the same crop or related crops are planted in consecutive years under normal management.
2. The Performance
2.1 Vegetable growth becomes weaker and yield decreases
With the increase of continuous cropping years, garlic showed a trend of first increasing and then decreasing.
2.2 Serious pests and diseases, quality decline
With the increase of continuous cropping years, the VC content, crude fiber content and soluble sugar content of leek all showed a downward trend; the plant height and leaf area of potato decreased year by year; the degree of pests and diseases of cucumber increased year by year.
3.Causes of Continuous Cropping Obstacles
3.1 Allelopathy
Crops release certain chemical substances to the environment and affect the growth and development of other crops, which is called allelopathy, including both promotion and inhibition;
Toxins secreted by roots and decomposed by branch and leaf residues are important factors affecting continuous cropping of vegetables. Crops release chemical substances into the environment through leaching, residue decomposition, and root secretion. These chemical substances will cause direct or indirect damage to the crop itself. This phenomenon is called autotoxicity.
3.2 Soil Nutrient Imbalance
The distribution range and depth of the root system of the same vegetable are the same, and the absorption ratio of various nutrients in the soil is also the same. After continuous cropping, it is easy to cause a certain nutrient deficiency in the soil, and the soil nutrient will be unbalanced. For example, more nitrogen can easily cause magnesium deficiency. Cucumber mesophyll chlorosis after magnesium deficiency, pepper leaf tip yellowing due to magnesium deficiency, etc.
3.3 Soil Salinization and Acidification
The soil in the shed cannot be irrigated by rainwater, the temperature is high, and the evaporation of soil water is large. The fertilizer and other salts in the lower soil layer rise along the capillary of the soil, forming a thin layer of white salt on the soil surface, that is, secondary salinization of the soil Phenomenon;
Secondary salinization of the soil will increase the concentration of the soil solution and increase the osmotic potential, which will lead to the weakening of the water and fertilizer absorption capacity of the vegetable root system, resulting in nutrient deficiency, stunted growth, and reduced yield and quality.
3.4 Changes in Root Microorganisms
The change of microorganisms in the soil is most closely related to continuous cropping obstacles;
4.Prevention Methods
4.1 Reasonable selection of cultivated soil
There are three types of soil texture: clay soil, loamy soil and sandy soil; clay soil has poor ventilation and water permeability; allelochemical substances have a strong inhibitory effect in the soil; sandy soil is easy to lose toxic substances, but has low fertility retention ; For vegetable farming, it is recommended to choose loamy soil with high fertility and good drainage.
4.2 Soil Improvement
Choose a suitable substrate for soilless cultivation, avoid continuous cropping obstacles and soil-borne diseases, reduce the amount of pesticides, save water, fertilizer and labor costs;
Improve soil salinization and acidification by washing salt with water;
For soils with a PH value less than 5.5, use quicklime to neutralize the acidity and reduce the content of nitrate nitrogen in the soil;
For soil with a PH value of 5.5 to 6.0, apply alkaline fertilizers such as plant ash;
For soil with a PH value greater than 7.5, apply an appropriate amount of acidic fertilizer.
4.3 Reasonable Fertilization
Long-term application of chemical fertilizers will cause soil compaction, poor air permeability, water permeability and fertilizer supply capacity, and promote the occurrence of diseases and insect pests;
In vegetable production, bio-organic fertilizers with specific low-cost, safe, and effective characteristics should be used to reduce and prevent soil salt accumulation, improve soil physical structure, increase microbial activity in soil, maintain soil fertility, and improve vegetable quality.
