The Salt And Water Movements & Biology Fertility Changes Under Seawater Irrigation In Seashore Saline Soil

Simulation was conducted to study the relative movement between salt and water of seashore saline soil. The first experiment was carried out in nigh undisturbed soil columns. The results were as follows: Under different rainfall intensity, the water movement in seashore saline soil was basically similar, and the whole process of water movement could be divided into two phases, namely rapidly decreasing phase of water suction and slowly-rising phase of water suction. The first phase in time was experienced more quickly, nevertheless the second more slowly. Meantime, the relationship between water suction and time can be expressed by a logarithmic equation, and its value amounted to most obvious lever in this experiment, but significant differences happened in those of salt movement. With different rainfall intensity, Httle rain had a great difficulty to render the salt in three-soil columns move, but moderate and heavy rain could induce the salt move from the upper-layers to sub-layers. The whole process of salt movement can also be divided into two phases: The first is a rapidly decreasing phase of salt, the other is a slowly increasing phase of salt, the second phase can also be expressed by a logarithmic equation. So almost no effects of desalination under little rain, having a certain effects of desalination in a short period of time under moderate rain, and a great effects of desalination in a long time under heavy rain.The second experiment was to study the Salinity Situation of Seashore Saline Soil under Seawater Irrigation. This experiment was carried out in fifteen undisturbed soil columns. The results were as follows: in summer, salt movement and distribution in the 0-40cm depth of seashore saline soil were very active, but salt in 40-120cm depth was relatively stable. Non-irrigating treatments had not salt peak being observed through the summer , and was in more stable situation of desalination. But it was happened to high temperature and evaporation , a low salt peak wound come into being. Although the salt movements and distribution in seawater irrigating treatments was very different from that in non-irrigating treatments. There would be a giant salt peak occurring in the 0-5cm depth and a low salt peak occurring in 5-40cm depth, however no salt peak being observed below 40cm depth of the columns. Further more, the higher concentration of the seawater was , and the longer intensive evaporation time lasted, the more sever the salt in topsoil was cumulated. In this experiment, action of main ions was also studied, Na+ was rapidly absorbed by the soil glue through Ca2+and Mg2+ exchange, so Na+ was very stable in bulk,on the contrary Ca2+ and Mg2+ were apt to leach out from the bulk. Act of Cl "was active, it was cumulated under high evaporation and leached by the rainfall and seawater irrigation. HCO3" was not very vulnerable by the outer condition changing. In addition, optimum seawater concentration used to irrigate saline soil could not make the soil cumulate soluble salt.The third experiment was to study the salt movement of Jiangsu seashore saline soil under open system. The materials in this experiment are also the three pieces of columns. The results showed: Under open system, salt in the columns moved from the uperlayers to the sublayers during the whole year, and most of it was leached into the groundwater. But many exclusive characteristics of salt movement was observed among the four quarters. In the first and second quarters, the salt in the columns in March and June was lost greatly because of the increasing rain, and salt movement of other months were stable. Entering into third quarter, salt was further leached from the buck soil for the sake of the heave rain, and the total salt in this quarter was the lowest of the year. In the last quarter, salt moved upward was predominant because of the evaporation. In a word, mechanisms of salt movement were summarized as follows: Salt in the columns was moving down and leached into the groundwater in March, June, July and August , however a...