Study On Harm Of Soil Secondary Salinization And Its Solution

In order to solve the soil secondary salinization in protected vegetables production, which caused by excessive fertilization, unblanced fertilization and unscientific irrigation et al. Lots of studies were carried out. However, the traditional studies to solve the soil secondary salinization took much time and labour and caused secondary pollution to the environment Therefore, the scientific and rational, environmental protection, high efficiency and low cost of improved ways should be found. In the current study, a survey of soil secondary salinization in jiangsu province was conducted, the effects of soil soluble salt in the secondary salinization of soil on the vegetable seedling emergence and growth was studies, the possible of reducing soluble salt content in the secondary salinization soil of using the carbon regulator was discussed, and the effect of carbon conditioner on vegetable growth and development in the secondary salinization of soil was also studied in the current study. The current results were as follows:(1) The investigation of protected soil salinity in Jiangsu Province showed that, the pH decreased by0.23～1.14units and acidified phenomenon was existed. Ca2+was the main part of cations in soil water which contribution to the total cation concentration nearly80%in the current. NO3-and SO42-contribution to the total anion concentration of56.8%and42.2%, respectively NO3-was not only main parts of anions but also main parts of the total water soluble salt. The average amount of NO3-accounted for45%of total water-soluble salts in the protected soil.(2)The vegetable needs a certain range of salt in the growth period, not the lower the better. Results showed that the emergence rate and shoot growth of Brassica chinensis seedlings was not affected by low salt content (4.12g·kg-1in the current study) under pot culture. However, with the increase of salt content, the seedling emergence rate, shoot biomass and root parameters including length, surface area and volume all significantly decreased. Brassica chinensis seeds could not emerge when the salt content reached14.98g·kg-1. When soil nitrate content was1623mg·kg-1, the nitrate accumulated in seedling body could reach up to7810mg·kg-1, which was much higher than national food sanitation standard of nitrate in vegetables, although the growth of the seedlings was not apparently affected. Based on this study, the soil containing nitrate higher than429mg·kg-1was not recommended for Brassica chinensis cultivation.(3)The main reason of secondary salinization was that the high applying of nitrogen fertilizer and it would lead to the accumulation of NO3-in the surface of soil. So the measures of decreasing the content of NO3-should be taken to repair this kind of soil. According to the theory of interaction of carbon and nitrogen by microorganism, the accumulation of NO3-caused by lacking of appropriate carbon source to accept the inorganic nitrogen source. In theory, under the participation of microorganisms, inorganic nitrogen could be converted to organic notrogen when the appropriate carbon source existed in soil. The process could decrease the content of NO3-in soil, and increase the CEC by increasing the content of organic matter in soil and decrease the content of salt which would be absorbed by soil to decrease the salt poisoning. The current results indicated that as long as the carbon regulator was added to the secondary salinization of soil, the concentration of nitrate in the soil solution were significantly decreased, regardless of the short-term cultivation and long term cultivation. Within a certain range, the amount of NO3-was decreasing with the increasing of the amount of carbon regulator, and it could decrease97.10%on the original concentration. These results indicated that adding avaiable carbon to secondary salinization of soil to reduce the content of NO3-was feasible. Compared with drip washing, the advantages of adding available carbon was that it could change the NO3-to organic nitrogen.(4)Compared with control treatment, the cabbage seedling emergence rate is92%at the treatment of36g·kg-1carbon regulator (T3treatment). During the late growth of cabbage, T3treatment had highest increase rate on fresh weight in all treatments, nearly334%, the growth was not affected; The root system at the treatment of48g·kg-1carbon regulator (T4treatment) was most developed, but stems and leaves of cabbage in late growth was inhibited. With the increased use of carbon regulator, the stem of cabbage showed the puper and the leaves became yellow, even withers away at the treatment of72g·kg-1.Thus, the amount of carbon regulators was not the more the better. Considering the economic benefits, the recommended dosage of carbon regulator was36g·kg-1(T3treatment).