Research On The Mechanism Of Re-formed Salted Soil In Protected Field

In this paper, salt contents in different protected fields were investigated in Quzhou county, Hebei province. By monitoring the salt content in a year round, we explored the changes of soil salt in three planting patterns and two types of protected fields. The results are as follows:(1) Total salt content in plough layer from vegetable fields in both Tasiqiao and Quzhou, where vegetables are mainly produced, was about 1.0g/kg³.0g/kg, falling in the scope of light degree salinity. Analysis showed that the value of salt content in 0⁵cm layer, where vegetables were planted for over 20 years, was as 1.3 times as that of neighboring grain fields. That is to say, the difference was remarkable. While in 5²0cm layer, the total salt in vegetable field was 2.0g/kg, which was about as 1.2 times as that in grain field. Although different planting systems can hardly affect the components of soil salt, the amount of salt ions changed a lot, among which the ions Cl^- and SO₄^2- kept increasing in vegetable fields.(3) Under the salinity condition, there was little difference in salt content between grain fields and plastic sheds which had been practiced less than 5 years. In contrast, the value was proportion to the using time over 5 years, especially the Cl" and SO₄^2- in 0⁵cm layer.(4) There was different salinity degree in greenhouse and plastic shed. Generally, the sequence was greenhouses > plastic sheds > grain fields. In 0²0cm, there were two salt accumulation periods, from March to April and November, While it was from March to May in plastic shed. In the mean time, there were two salt accumulation periods: spring and fall in greenhouse, and one in plastic shed: from May to August.(5) Compared with nearby grain fields, the salt content in conventional pattern, which was as 1.55 times as that in grain fields in 0²0cm layer during salt accumulation period, was the highest among the three different patterns. According to the annual monitoring, on one hand, there were two accumulation periods (one is in spring, the other is in fall) and one desalinity period lasting for four months in conventional and integrated patterns. On the other hand, the second accumulation period lasted from July to November in organic pattern. No obvious difference can be seen between organic pattern and integrated pattern. There was the largest range in conventional pattern with 0.8g/kg.