In some plants,stems and leaves appear scorching and shrinking,and some even die.Some pest structures also change.This is what the performance of continuous cropping obstacle in different crops. 

 The reasons are generally the following aspects: 

1.Continuous cropping causes symptoms of deficiency in soil

Field crops have a long reproductive cycle.The vegetable has a short growing period and a high multiple cropping index. However,whether the same crop or vegetable is grown on the same land for a long or short period,it will absorb more elements, and the element in the soil will be in short supply.Some will also lead to changes in the pH of the soil,and the availability of certain elements in the soil will also decrease.As a result, some cotton will have potassium deficiency,some cabbage will have calcium deficiency, and some will suffer from Zinc Magnesium deficiency. 

2.Serious harm of pests and Pathogens in soil

The common diseases in continuous cropping fields are infectious diseases and viruses;the pests are mainly nematodes.Most of the viruses are overwintering on the weeds in the fields and often become sources of infection.The vegetables that are endangered include cabbage,cucumber,tomato,pepper,and radish.Infectious diseases include blight,bacterial wilt,soft rot,and sclerotia. They can live in the soil for many years and occur when conditions are suitable.Such as cotton is easy to wilt if continuours rain in budding,flowering period,rape is susceptible to sclerotinia. 

3.Decrease of organic matter content

In the field of continuous cropping,some microorganisms are relatively active, and the decomposition of soil organic matter is fast and the utilization rate is high.Therefore,soil porosity decreases, soil buffer capacity decreases,nutrient loss increases,and the ratio of nutrients also becomes imbalanced.As a result,soil physicochemical properties and the biological character deteriorated.In order to mitigate the negative impact of continuous cropping,comprehensive adjustments and governance should be implemented in preventive measures. 

 Management solution 

1.Carry out “Crop Rotation”

For field crops or vegetable that have caused serious damage to virus sources and infectious diseases,two to three years of crop rotation should be implemented.It is best to use paddy crop rotations to better prevent diseases. 

2.Increase application of organic fertilizer

Each hectare should be applied with 60-75 MT decomposing home-fertilizer,or 37.5-45MT of bio-organic fertilizer, or 1200-2250 kg of bio-organic compound fertilizer,which can improve soil organic matter content and inhibit the activities of some harmful microorganisms.At the same time, according to the needs of different crops,applying a certain amount of potash fertilizer in organic fertilizer can alleviate or reduce the damage to wilt disease. 

3.Use microbial technology

Microbial agents(such as Trichoderma harzianum,Bacillus subtilis) can be used to irrigate roots or spray,which can improve soil condition obviously,control soil-borne pathogens,promote the growth of crop roots,increase traditional fertilizer efficiency,enhance crops stress resistance,and better prevent diseases caused by continuous cropping,thus increase yield and improve quality. 

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