How soil salt damage occurs

1. Fertilizer application dosage

Many vegetable farmers and fruit farmers think: big input will have big output, and thus in the use of fertilizer regardless of whether the vegetables can be used in full, the amount of fertilizer, so not only can not improve the yield, but also for vegetables is a big threat. The application of chicken and duck manure in large quantities, instead of lifting the soil salinity, will have the opposite effect. And fertilizer and chicken and duck manure into the soil, part of the mineral nutrients are absorbed by the crop, part of the leaching in the deep soil or water, there is a considerable part of the residue in the soil surface, year after year, the greenhouse because of the shed film cover, difficult to use and water leaching and degradation, the accumulation of salt more and more, soil salinization phenomenon is bound to occur. In particular, the application of ammonium nitrate and other excessive amounts, so that the soil tillage layer salt content increased. In the application of human and animal fertilizer in the shed, due to the high temperature in the shed, human and animal manure quickly volatile decomposition, sulfide, nitrate and other organic salts and inorganic salts and other residues caused by soil salinization.

2. Fertilization ratio is out of proportion

In actual production, vegetable farmers to improve vegetable production blindly a large number of fertilizers, and partial application of nitrogen, phosphorus, potassium fertilizer, do not pay attention to the application of trace elements. The ratio of organic fertilizer and chemical fertilizer is out of balance, fertilizer input utilization rate is very low. At present, the amount of chemical fertilizer has been higher, but also a large number of applications of unrotted chicken and duck manure and other organic fertilizers, but ignore the application of straw, stable manure, organic fertilizers, biological fertilizers, chicken and duck manure without fermentation and decomposition, it is easy to cause salt damage.

3. Special environment

Greenhouse almost year-round use of plastic film cover, long-term no precipitation flushing, artificial application of a large number of chemical fertilizers can not be infiltrated with the rain to the deep soil, and high temperature in the greenhouse, the evaporation of soil moisture, fertilizer in the salt is easy to rise with the moisture, rising to the soil tillage layer, when the salt accumulates to a certain extent will produce salt damage to crops.

4. High soil moisture

The greenhouse itself is a closed or semi-closed environment, coupled with frequent watering and fertilization in the greenhouse, the surface soil moisture is large, seriously damaging the soil granular structure, large pore space is reduced, the soil infiltration capacity is reduced and easy to form a plate, resulting in the soil surface salt can not penetrate into the deep soil layer. Especially in low-lying greenhouses, the soil humidity is too large, the permeability decreases, resulting in soil salinization.

In the case of insufficient organic matter content in the soil, the long-term blind over-application of chemical fertilizers is bound to cause the deposition of chemical elements in the soil, which will inevitably result in the occurrence of salt damage. Salt damage is a combination of soil type, irrigation water quality, inappropriate application of chemical fertilizers and differences in salt tolerance of planted crops, which can lead to wilting, dead trees and sterile growth and development.

Soil salt damage has light and heavy, commonly used ground observation and laboratory analysis of two methods to determine: salt damage of the initial ground frost and later developed to green moss, when the laboratory soil salt amount of 0.189-0.255%, shed field crops are still normal; soil salt heavy ground white crystalline "salt frost", shed vegetable seedlings When the ground appears "red frost", shed field crops in the middle of the spot wilt, at this time, chemical analysis of soil salinity has reached 0.315-0.378%.

When the shed field wilted and died, the whole salt amount has been as high as 0.378-0.441%, the soil solution osmotic pressure is high, the whole root system like soaking in a pickle jar, it is easy to cause root water backflow, reverse osmosis, root cortex red, stem shrinkage, crop root rot, dehydration and death.